Differential Equations in Pumas

Author

David Widmann

1 Introduction

Pumas automatically chooses a differential equation solver that is suitable for the simulation or estimation of the dynamical system of the NLME (Nonlinear Mixed Effects) model at hand. This default solver is the preferred choice and optimized for most users and use cases. Nevertheless, in some cases the performance-accuracy trade-off can be improved by adjusting the tolerances, or possibly even the algorithm, of the differential equation solver.

In this tutorial, the Warfarin PK/PD model is used to demonstrate how to configure the differential equation solver.

2 Learning Goals

  • Observe the utility of the @vars block of a Pumas model with respect to storing dynamic variables associated with differential equations
  • Understand the main differences between common differential equation solvers for nonlinear dynamical systems
  • Learn how to adjust the algorithm and the tolerances of the differential equation solver

3 Warfarin PK/PD Model

We return to the Warfarin PK/PD model. Its dynamical system consists of three states, \(\operatorname{Depot}\), \(\operatorname{Central}\), and \(\operatorname{Turnover}\), whose dynamics are governed by the ordinary differential equations:

\[ \begin{aligned} \operatorname{Depot}'(t) &= - \operatorname{Ka} \operatorname{Depot}(t),\\ \operatorname{Central}'(t) &= \operatorname{Ka} \operatorname{Depot}(t) - \frac{\operatorname{CL}}{\operatorname{Vc}} \operatorname{Central}(t),\\ \operatorname{Turnover}'(t) &= \operatorname{rin} (1 + \operatorname{emax} \frac{\operatorname{Central}(t) / \operatorname{Vc}}{\operatorname{c50} + \operatorname{Central}(t)/\operatorname{Vc}}) - \operatorname{kout} \operatorname{Turnover}(t) \end{aligned} \]

with PK parameters \(\operatorname{Ka}\) (absorption rate), \(\operatorname{CL}\) (clearance), and \(\operatorname{Vc}\) (volume of distribution) and PD parameters \(\operatorname{rin}\), \(\operatorname{emax}\), \(\operatorname{c50}\), and \(\operatorname{kout}\).

The dynamical system can be written more concisely by introducing auxiliary variables for repeated expressions:

\[ \begin{aligned} \operatorname{Depot}'(t) &= -\operatorname{ratein}(t),\\ \operatorname{Central}'(t) &= \operatorname{ratein}(t) - \operatorname{CL} \operatorname{cp}(t),\\ \operatorname{Turnover}'(t) &= \operatorname{rin} \operatorname{pd}(t) - \operatorname{kout} \operatorname{Turnover}(t) \end{aligned} \]

with influx rate \(\operatorname{ratein}(t) := \operatorname{Ka} \operatorname{Depot}(t)\), concentration \(\operatorname{cp}(t) := \operatorname{Central}(t) / \operatorname{Vc}\), and \(\operatorname{pd}(t) := 1 + \operatorname{emax} \frac{\operatorname{cp}(t)}{\operatorname{c50} + \operatorname{cp}(t)}\).

4 Auxiliary Variables in @vars

In Pumas, dynamical systems are defined in the @dynamics block inside of the @model definition. For instance, the dynamical system of the Warfarin PK/PD model can be implemented as follows:

warfarin_pkpd_model = @model begin
    ...

    @dynamics begin
        Depot' = -Ka * Depot
        Central' = Ka * Depot - CL / Vc * Central
        Turnover' =
            rin * (1 + emax * (Central / Vc) / (cp50 + Central / Vc)) - kout * Turnover
    end

    ...
end

The same concise rewriting can be applied in a Pumas @model by defining auxiliary variables (“aliases”) in the @vars block:

warfarin_pkpd_model = @model begin
    ...

    @vars begin
        cp := Central / Vc
        ratein := Ka * Depot
        pd := 1 + emax * cp / (c50 + cp)
    end

    @dynamics begin
        Depot' = -ratein
        Central' = ratein - CL * cp
        Turnover' = rin * pd - kout * Turnover
    end

    ...
end
Tip

The walrus operator (:=) ensures that the aliases do not show up in the simulation output of the model. However, if you would like to access an alias in the simulation output, you should define the alias with =. For instance, if you want to obtain concentration cp as part of the simulation output, you can change the @vars block to

@vars begin
    cp = Central / Vc
    ratein := Ka * Depot
    pd := 1 + emax * cp / (c50 + cp)
end

5 Differential Equation Solvers

The differential equation in the Warfarin model is non-linear, as detected by Pumas (“Dynamical system type: Nonlinear ODE”):

using Pumas

warfarin_pkpd_model = @model begin
    @param begin
        # PK parameters
        """
        Clearance (L/h/70kg)
        """
        pop_CL  RealDomain(lower = 0.0, init = 0.134)
        """
        Central Volume L/70kg
        """
        pop_V  RealDomain(lower = 0.0, init = 8.11)
        """
        Absorption time (h)
        """
        pop_tabs  RealDomain(lower = 0.0, init = 0.523)
        """
        Lag time (h)
        """
        pop_lag  RealDomain(lower = 0.0, init = 0.1)
        # PD parameters
        """
        Baseline
        """
        pop_e0  RealDomain(lower = 0.0, init = 100.0)
        """
        Emax
        """
        pop_emax  RealDomain(init = -1.0)
        """
        EC50
        """
        pop_c50  RealDomain(lower = 0.0, init = 1.0)
        """
        Turnover
        """
        pop_tover  RealDomain(lower = 0.0, init = 14.0)
        # Inter-individual variability
        """
          - ΩCL
          - ΩVc
          - ΩTabs
        """
        pk_Ω  PDiagDomain([0.01, 0.01, 0.01])
        """
          - Ωe0
          - Ωemax
          - Ωec50
          - Ωturn
        """
        pd_Ω  PDiagDomain([0.01, 0.01, 0.01, 0.01])
        # Residual variability
        """
        Proportional residual error for drug concentration
        """
        σ_prop  RealDomain(lower = 0.0, init = 0.00752)
        """
        Additive residual error for drug concentration (mg/L)
        """
        σ_add  RealDomain(lower = 0.0, init = 0.0661)
        """
        Additive error for PCA
        """
        σ_fx  RealDomain(lower = 0.0, init = 0.01)
    end

    @random begin
        # mean = 0, covariance = pk_Ω
        pk_η ~ MvNormal(pk_Ω)
        # mean = 0, covariance = pd_Ω
        pd_η ~ MvNormal(pd_Ω)
    end

    @covariates FSZV FSZCL

    @pre begin
        # PK
        CL = FSZCL * pop_CL * exp(pk_η[1])
        Vc = FSZV * pop_V * exp(pk_η[2])
        tabs = pop_tabs * exp(pk_η[3])
        Ka = log(2) / tabs
        # PD
        e0 = pop_e0 * exp(pd_η[1])
        emax = pop_emax * exp(pd_η[2])
        c50 = pop_c50 * exp(pd_η[3])
        tover = pop_tover * exp(pd_η[4])
        kout = log(2) / tover
        rin = e0 * kout
        time = t
    end

    @dosecontrol begin
        lags = (Depot = pop_lag,)
    end

    @init begin
        Turnover = e0
    end

    # aliases for use in @dynamics and @derived
    @vars begin
        cp := Central / Vc
        ratein := Ka * Depot
        pd := 1 + emax * cp / (c50 + cp)
    end

    @dynamics begin
        Depot' = -ratein
        Central' = ratein - CL * cp
        Turnover' = rin * pd - kout * Turnover
    end

    @derived begin
        """
        Warfarin Concentration (mg/L)
        """
        conc ~ @. Normal(cp, sqrt((σ_prop * cp)^2 + σ_add^2))
        """
        PCA
        """
        pca ~ @. Normal(Turnover, σ_fx)
    end
end
PumasModel
  Parameters: pop_CL, pop_V, pop_tabs, pop_lag, pop_e0, pop_emax, pop_c50, pop_tover, pk_Ω, pd_Ω, σ_prop, σ_add, σ_fx
  Random effects: pk_η, pd_η
  Covariates: FSZV, FSZCL
  Dynamical system variables: Depot, Central, Turnover
  Dynamical system type: Nonlinear ODE
  Derived: conc, pca
  Observed: conc, pca

Pumas approximates the solution of the differential equation with a numerical differential equation solver. Generally, one distinguishes between solvers for stiff and non-stiff differential equations.

5.1 Stiff vs. Non-Stiff Systems

A key distinction among numerical solvers is whether they are designed for stiff or non-stiff differential equations:

  • Non-Stiff Differential Equations: These systems exhibit relatively moderate changes in their variables. Standard non-stiff solvers can efficiently approximate solutions of these systems.

  • Stiff Differential Equations: These systems contain rapidly changing components alongside more slowly varying dynamics. Non-stiff solvers typically perform poorly on stiff systems, as they may require exceedingly small step sizes to maintain numerical stability. Specialized stiff solvers are therefore employed to handle the sharp gradients and large timescale differences without compromising accuracy.

6 Pumas’s Automatic Solver Selection

By default, Pumas adopts a hybrid approach with automatic stiffness detection to switch between stiff and non-stiff solvers as needed.

  • Default Solvers: Rodas5P (stiff) and Vern7 (non-stiff)
  • Tolerances: Relative tolerance \(10^{-8}\) and absolute tolerance \(10^{-12}\)
  • Rationale: These tolerances ensure high precision during both simulation and parameter estimation, which is critical for accurate exploratory and predictive modeling and matching the model’s predictions to observed data.

The default solvers and tolerances are recommended for most users in most instances. If desired, however, it is possible to adjust these settings with the diffeq_options keyword argument.

Important

Computation time decreases as tolerances are increased. However, higher tolerances come at the cost of a less strict error control, and hence generally a less accurate solution.

6.1 Adjusting the Tolerances

The absolute and relative tolerance of the solver can be specified with abstol and reltol.

7 Absolute and Relative Tolerances

When employing a numerical solver, it is necessary to specify how accurately the solution should be computed. This precision is controlled by two key parameters:

  1. Absolute Tolerance \((\text{abstol})\)

    • Interpreted as the maximum allowable error when the solution values are near zero.
    • Ensures that numerical approximations stay within a reasonable bound, preventing physically impossible outcomes (e.g., negative concentrations) or excessive drift at small scales.
    • For instance, an absolute tolerance of \(10^{-6}\) means the solver attempts to keep the absolute error below \(10^{-6}\) whenever the solution magnitude is close to zero.
  2. Relative Tolerance \((\text{reltol})\)

    • Enforces the number of correct digits throughout the simulation, effectively controlling error relative to the current scale of the solution.
    • For example, a relative tolerance of \(10^{-3}\) implies the solver aims for three correct decimal places (i.e., the solution is accurate to within 0.1% of its current magnitude).
    • As the solution grows or shrinks, the solver adjusts its time-step size and internal computations to maintain this relative accuracy.

Sometimes decreasing tolerances can help to reduce numerical problems, e.g. to keep solutions non-negative that are mathematically guaranteed to be non-negative. Additionally, the choice of tolerances can be motivated by the application of the numerical solution: For plotting a less accurate solution, and hence larger tolerances, might be tolerable, whereas typically for model fitting a more accurate solution, and hence smaller tolerances, are beneficial.

This can be demonstrated when fitting the Warfarin model with an example dataset: Optimization fails with large tolerances of 1e-3 (relative) and 1e-6 (absolute)

fit(
    warfarin_pkpd_model,
    pop,
    init_params(warfarin_pkpd_model),
    FOCE();
    diffeq_options = (; reltol = 1e-3, abstol = 1e-6),
)
[ Info: Checking the initial parameter values.
[ Info: The initial negative log likelihood and its gradient are finite. Check passed.
Iter     Function value   Gradient norm 
     0     3.130181e+06     5.915753e+06
 * time: 0.04384589195251465
     1     5.185877e+05     8.742010e+05
 * time: 4.800498008728027
     2     3.866957e+05     6.366584e+05
 * time: 5.858506917953491
     3     1.795019e+05     2.835377e+05
 * time: 6.889288902282715
     4     9.682619e+04     1.546512e+05
 * time: 7.811128854751587
     5     4.791898e+04     6.820022e+04
 * time: 8.696491956710815
     6     2.907369e+04     3.509683e+04
 * time: 9.584167003631592
     7     1.827377e+04     1.713122e+04
 * time: 10.537323951721191
     8     1.260634e+04     9.563328e+03
 * time: 11.51173996925354
     9     9.403430e+03     8.611643e+03
 * time: 12.472425937652588
    10     7.325839e+03     7.634814e+03
 * time: 13.432734966278076
    11     5.926864e+03     6.625143e+03
 * time: 14.379194021224976
    12     4.942276e+03     5.562817e+03
 * time: 15.294863939285278
    13     4.139082e+03     4.326560e+03
 * time: 16.210917949676514
    14     3.563490e+03     3.065255e+03
 * time: 17.130348920822144
    15     3.296158e+03     2.170246e+03
 * time: 18.04499387741089
    16     3.216281e+03     1.669628e+03
 * time: 18.94379496574402
    17     3.205943e+03     1.487868e+03
 * time: 19.84991693496704
    18     3.204981e+03     1.444253e+03
 * time: 20.740763902664185
    19     3.204107e+03     1.417661e+03
 * time: 21.6385760307312
    20     3.201145e+03     1.361617e+03
 * time: 22.526020050048828
    21     3.194218e+03     1.282918e+03
 * time: 23.41675901412964
    22     3.175799e+03     1.158036e+03
 * time: 24.306293964385986
    23     3.130001e+03     9.774722e+02
 * time: 25.199190855026245
    24     3.016853e+03     7.265878e+02
 * time: 26.08452796936035
    25     2.749857e+03     4.107604e+02
 * time: 26.950739860534668
    26     2.137213e+03     2.318395e+02
 * time: 27.82140588760376
    27     1.756667e+03     2.281482e+02
 * time: 28.753108978271484
    28     1.380674e+03     1.613751e+02
 * time: 31.269019842147827
    29     1.328451e+03     1.298787e+02
 * time: 32.153708934783936
    30     1.287368e+03     2.435586e+02
 * time: 32.927605867385864
    31     1.263071e+03     1.616831e+02
 * time: 33.70522093772888
    32     1.254713e+03     1.796576e+02
 * time: 34.47108602523804
    33     1.247205e+03     1.996165e+02
 * time: 35.249754905700684
    34     1.243765e+03     1.938235e+02
 * time: 36.01481890678406
    35     1.240829e+03     1.739538e+02
 * time: 36.821568965911865
    36     1.240788e+03     1.744028e+02
 * time: 37.61355495452881
    37     1.240776e+03     1.743250e+02
 * time: 38.374022006988525
    38     1.240093e+03     1.687609e+02
 * time: 39.156182050704956
    39     1.239010e+03     1.586878e+02
 * time: 39.94395089149475
    40     1.236253e+03     1.305335e+02
 * time: 40.725817918777466
    41     1.232129e+03     8.229601e+01
 * time: 41.49223184585571
    42     1.228151e+03     3.735809e+01
 * time: 42.286757946014404
    43     1.226337e+03     5.238476e+01
 * time: 43.06374502182007
    44     1.226025e+03     4.868885e+01
 * time: 43.839536905288696
    45     1.226011e+03     4.583328e+01
 * time: 44.60988783836365
    46     1.226010e+03     4.536419e+01
 * time: 45.36117887496948
    47     1.226008e+03     4.466378e+01
 * time: 46.093708992004395
    48     1.226002e+03     4.336406e+01
 * time: 46.8202919960022
    49     1.225988e+03     4.102579e+01
 * time: 47.591376066207886
    50     1.225951e+03     3.656289e+01
 * time: 48.337640047073364
    51     1.225858e+03     2.865017e+01
 * time: 49.08858799934387
    52     1.225645e+03     2.863717e+01
 * time: 49.82658004760742
    53     1.225243e+03     3.015495e+01
 * time: 50.56348991394043
    54     1.224739e+03     4.057375e+01
 * time: 51.30551099777222
    55     1.224438e+03     5.072098e+01
 * time: 52.047581911087036
    56     1.224368e+03     4.561543e+01
 * time: 52.78227496147156
    57     1.224362e+03     4.124686e+01
 * time: 53.51751685142517
    58     1.224360e+03     4.008283e+01
 * time: 54.23265790939331
    59     1.224357e+03     3.807281e+01
 * time: 54.962846994400024
    60     1.224349e+03     3.507733e+01
 * time: 55.69300293922424
    61     1.224328e+03     3.152658e+01
 * time: 56.422492027282715
    62     1.224274e+03     2.940378e+01
 * time: 57.15742087364197
    63     1.224133e+03     2.814508e+01
 * time: 57.90731406211853
    64     1.223771e+03     2.816089e+01
 * time: 58.659225940704346
    65     1.222880e+03     4.493737e+01
 * time: 59.386653900146484
    66     1.220919e+03     8.628817e+01
 * time: 60.11530685424805
    67     1.217683e+03     1.137018e+02
 * time: 60.822242975234985
    68     1.214493e+03     9.066168e+01
 * time: 61.523202896118164
    69     1.212820e+03     8.381803e+01
 * time: 62.23194599151611
    70     1.212582e+03     8.589808e+01
 * time: 62.942939043045044
    71     1.212574e+03     8.557497e+01
 * time: 63.65787601470947
    72     1.212569e+03     8.522111e+01
 * time: 64.3703088760376
    73     1.212552e+03     8.416219e+01
 * time: 65.09645986557007
    74     1.212516e+03     8.236925e+01
 * time: 65.78960490226746
    75     1.212415e+03     7.841477e+01
 * time: 66.49769997596741
    76     1.212165e+03     7.017247e+01
 * time: 67.2089569568634
    77     1.211553e+03     5.231312e+01
 * time: 67.90825605392456
    78     1.210236e+03     7.254984e+01
 * time: 68.65167498588562
    79     1.208052e+03     8.652548e+01
 * time: 69.39358687400818
    80     1.205978e+03     9.811810e+01
 * time: 70.15770292282104
    81     1.205158e+03     1.085052e+02
 * time: 70.88729596138
    82     1.205038e+03     9.706885e+01
 * time: 71.62432098388672
    83     1.205030e+03     9.297156e+01
 * time: 72.3486750125885
    84     1.205025e+03     9.142093e+01
 * time: 73.07483005523682
    85     1.205007e+03     8.794517e+01
 * time: 73.78387498855591
    86     1.204968e+03     8.329868e+01
 * time: 74.49967193603516
    87     1.204860e+03     7.519245e+01
 * time: 75.22060203552246
    88     1.204586e+03     6.676950e+01
 * time: 75.9117419719696
    89     1.203889e+03     5.914985e+01
 * time: 76.60696792602539
    90     1.202275e+03     5.659425e+01
 * time: 77.29526901245117
    91     1.199277e+03     5.457598e+01
 * time: 77.99242401123047
    92     1.195791e+03     6.434187e+01
 * time: 78.654217004776
    93     1.193281e+03     4.404726e+01
 * time: 79.30896401405334
    94     1.192403e+03     4.696513e+01
 * time: 79.99026799201965
    95     1.192344e+03     4.826238e+01
 * time: 80.6446099281311
    96     1.192341e+03     4.836346e+01
 * time: 81.28319597244263
    97     1.192340e+03     4.843134e+01
 * time: 81.91030597686768
    98     1.192336e+03     4.854905e+01
 * time: 82.53473091125488
    99     1.192325e+03     4.873525e+01
 * time: 83.16785407066345
   100     1.192297e+03     4.901993e+01
 * time: 83.80186891555786
   101     1.192226e+03     4.941568e+01
 * time: 84.45286893844604
   102     1.192043e+03     4.985206e+01
 * time: 85.13519406318665
   103     1.191593e+03     5.001007e+01
 * time: 85.81375885009766
   104     1.190562e+03     4.892711e+01
 * time: 86.50051784515381
   105     1.188621e+03     4.482401e+01
 * time: 87.18688797950745
   106     1.186171e+03     5.565401e+01
 * time: 87.89409184455872
   107     1.184411e+03     7.195267e+01
 * time: 88.60426092147827
   108     1.183640e+03     7.480949e+01
 * time: 89.31642889976501
   109     1.183456e+03     7.309347e+01
 * time: 90.02860593795776
   110     1.183420e+03     7.276593e+01
 * time: 90.69497489929199
   111     1.183410e+03     7.363637e+01
 * time: 91.36429691314697
   112     1.183407e+03     7.448590e+01
 * time: 92.02231287956238
   113     1.183403e+03     7.577977e+01
 * time: 92.6972029209137
   114     1.183397e+03     7.712667e+01
 * time: 93.35962700843811
   115     1.183377e+03     7.953569e+01
 * time: 94.04420304298401
   116     1.183329e+03     8.300885e+01
 * time: 94.7211389541626
   117     1.183203e+03     8.805322e+01
 * time: 95.40114188194275
   118     1.182889e+03     9.423584e+01
 * time: 96.0783679485321
   119     1.182143e+03     9.919011e+01
 * time: 96.78499484062195
   120     1.180607e+03     9.577147e+01
 * time: 97.48721385002136
   121     1.178255e+03     7.337696e+01
 * time: 98.20086002349854
   122     1.176240e+03     3.404284e+01
 * time: 98.91404485702515
   123     1.175531e+03     1.922941e+01
 * time: 99.66240191459656
   124     1.175410e+03     1.933203e+01
 * time: 100.41189885139465
   125     1.175396e+03     1.964875e+01
 * time: 101.1775050163269
   126     1.175395e+03     1.966957e+01
 * time: 101.91872787475586
   127     1.175394e+03     1.960524e+01
 * time: 102.67614102363586
   128     1.175394e+03     1.957692e+01
 * time: 103.43248701095581
   129     1.175392e+03     1.945993e+01
 * time: 104.1843490600586
   130     1.175387e+03     1.938252e+01
 * time: 104.9326388835907
   131     1.175374e+03     1.915643e+01
 * time: 105.6806709766388
   132     1.175342e+03     1.892407e+01
 * time: 106.40796899795532
   133     1.175256e+03     1.840907e+01
 * time: 107.15405106544495
   134     1.175030e+03     1.936487e+01
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   135     1.174436e+03     2.656836e+01
 * time: 108.62122201919556
   136     1.172888e+03     3.906036e+01
 * time: 109.38319206237793
   137     1.169012e+03     5.824500e+01
 * time: 110.14776802062988
   138     1.160858e+03     7.724789e+01
 * time: 110.91178393363953
   139     1.151984e+03     5.979641e+01
 * time: 111.69499707221985
   140     1.150239e+03     2.132816e+02
 * time: 112.49608302116394
   141     1.147461e+03     1.267649e+02
 * time: 113.29408288002014
   142     1.143928e+03     2.373475e+01
 * time: 114.07671189308167
   143     1.142853e+03     2.225755e+01
 * time: 114.83840084075928
   144     1.141788e+03     3.914831e+01
 * time: 115.57437086105347
   145     1.141298e+03     2.253303e+01
 * time: 116.30886507034302
   146     1.140996e+03     2.098978e+01
 * time: 117.05825805664062
   147     1.140981e+03     2.094768e+01
 * time: 117.79100894927979
   148     1.140978e+03     2.098189e+01
 * time: 118.50924491882324
   149     1.140977e+03     2.101184e+01
 * time: 119.22071695327759
   150     1.140977e+03     2.100810e+01
 * time: 119.98072695732117
   151     1.140977e+03     2.097542e+01
 * time: 120.68533205986023
   152     1.140976e+03     2.094478e+01
 * time: 121.36990284919739
   153     1.140974e+03     2.089055e+01
 * time: 122.10394096374512
   154     1.140970e+03     2.083449e+01
 * time: 122.86092400550842
   155     1.140963e+03     2.076312e+01
 * time: 123.57725095748901
   156     1.140944e+03     2.068373e+01
 * time: 124.29382300376892
   157     1.140896e+03     2.060201e+01
 * time: 125.06949806213379
   158     1.140770e+03     2.053295e+01
 * time: 125.81379389762878
   159     1.140444e+03     2.051792e+01
 * time: 126.77110385894775
   160     1.139610e+03     2.178464e+01
 * time: 127.88144898414612
   161     1.138121e+03     3.276681e+01
 * time: 129.08301901817322
   162     1.135107e+03     4.596086e+01
 * time: 130.29972791671753
   163     1.132128e+03     5.673428e+01
 * time: 131.31528687477112
   164     1.130311e+03     6.297114e+01
 * time: 132.17991590499878
   165     1.126112e+03     1.303349e+02
 * time: 132.98048901557922
   166     1.116080e+03     4.102784e+01
 * time: 133.94178700447083
   167     1.114892e+03     3.653943e+01
 * time: 134.82184386253357
   168     1.112342e+03     3.437496e+01
 * time: 135.6621880531311
   169     1.111707e+03     1.636383e+01
 * time: 136.52938985824585
   170     1.111291e+03     9.909471e+00
 * time: 137.40249705314636
   171     1.111206e+03     1.001147e+01
 * time: 138.2972309589386
   172     1.111191e+03     1.040660e+01
 * time: 139.18353605270386
FittedPumasModel

Dynamical system type:               Nonlinear ODE
Solver(s): (OrdinaryDiffEqVerner.Vern7,OrdinaryDiffEqRosenbrock.Rodas5P)

Number of subjects:                             32

Observation records:         Active        Missing
    conc:                       251             47
    pca:                        232             66
    Total:                      483            113

Number of parameters:      Constant      Optimized
                                  0             18

Likelihood approximation:                     FOCE
Likelihood optimizer:                         BFGS

Termination Reason:                      NoXChange
Log-likelihood value:                   -1111.1914

-----------------------
            Estimate
-----------------------
pop_CL       0.13526
pop_V        7.9651
pop_tabs     0.61589
pop_lag      0.86532
pop_e0      96.343
pop_emax    -1.085
pop_c50      1.6306
pop_tover   14.55
pk_Ω₁,₁      0.11739
pk_Ω₂,₂      0.03428
pk_Ω₃,₃      0.24153
pd_Ω₁,₁      0.0029639
pd_Ω₂,₂      0.0022284
pd_Ω₃,₃      0.02459
pd_Ω₄,₄      0.015792
σ_prop       0.013052
σ_add        0.81408
σ_fx         3.5163
-----------------------

but fares much better with lower tolerances of 1e-8 (relative) and 1e-12 (absolute):

fit(
    warfarin_pkpd_model,
    pop,
    init_params(warfarin_pkpd_model),
    FOCE();
    diffeq_options = (; reltol = 1e-8, abstol = 1e-12),
)
[ Info: Checking the initial parameter values.
[ Info: The initial negative log likelihood and its gradient are finite. Check passed.
Iter     Function value   Gradient norm 
     0     3.125741e+06     5.911802e+06
 * time: 2.5987625122070312e-5
     1     5.174461e+05     8.708698e+05
 * time: 2.2354819774627686
     2     3.865265e+05     6.344302e+05
 * time: 4.204480886459351
     3     1.804274e+05     2.829723e+05
 * time: 6.008337020874023
     4     9.706640e+04     1.550547e+05
 * time: 7.893967866897583
     5     4.769637e+04     6.778818e+04
 * time: 9.764966011047363
     6     2.902319e+04     3.499747e+04
 * time: 11.628520011901855
     7     1.823472e+04     1.705751e+04
 * time: 13.471780061721802
     8     1.258819e+04     9.569381e+03
 * time: 15.302196025848389
     9     9.389984e+03     8.615851e+03
 * time: 17.16966485977173
    10     7.314702e+03     7.636883e+03
 * time: 19.061110019683838
    11     5.916029e+03     6.624325e+03
 * time: 20.895668983459473
    12     4.930519e+03     5.558140e+03
 * time: 22.727866888046265
    13     4.125060e+03     4.315759e+03
 * time: 24.570483922958374
    14     3.549280e+03     3.051093e+03
 * time: 26.38404893875122
    15     3.283489e+03     2.157292e+03
 * time: 28.173277854919434
    16     3.204886e+03     1.659798e+03
 * time: 29.878135919570923
    17     3.194875e+03     1.480528e+03
 * time: 31.56321406364441
    18     3.193944e+03     1.437921e+03
 * time: 33.2578330039978
    19     3.193070e+03     1.411186e+03
 * time: 34.94093894958496
    20     3.190129e+03     1.355327e+03
 * time: 36.62148404121399
    21     3.183228e+03     1.276603e+03
 * time: 38.30476403236389
    22     3.164897e+03     1.151838e+03
 * time: 39.96260905265808
    23     3.119250e+03     9.712651e+02
 * time: 41.63005089759827
    24     3.006297e+03     7.204342e+02
 * time: 43.24989295005798
    25     2.738913e+03     4.050545e+02
 * time: 44.8462860584259
    26     2.123834e+03     2.318194e+02
 * time: 46.306967973709106
    27     1.789138e+03     2.290465e+02
 * time: 47.85612893104553
    28     1.396455e+03     1.683969e+02
 * time: 51.94181489944458
    29     1.333545e+03     1.336195e+02
 * time: 53.567774057388306
    30     1.297771e+03     2.452189e+02
 * time: 54.927698850631714
    31     1.266002e+03     1.523968e+02
 * time: 56.28854584693909
    32     1.255506e+03     1.733993e+02
 * time: 57.656753063201904
    33     1.247789e+03     1.971624e+02
 * time: 59.02541399002075
    34     1.244490e+03     1.915728e+02
 * time: 60.38836693763733
    35     1.240568e+03     1.704250e+02
 * time: 61.776084899902344
    36     1.240503e+03     1.711787e+02
 * time: 63.15067791938782
    37     1.240492e+03     1.711657e+02
 * time: 64.49610495567322
    38     1.239992e+03     1.687240e+02
 * time: 65.876620054245
    39     1.239199e+03     1.624610e+02
 * time: 67.28721785545349
    40     1.236971e+03     1.400044e+02
 * time: 68.68989896774292
    41     1.233203e+03     9.442277e+01
 * time: 70.0905499458313
    42     1.228682e+03     3.273922e+01
 * time: 71.4747359752655
    43     1.226466e+03     4.997778e+01
 * time: 72.85972690582275
    44     1.226104e+03     4.904407e+01
 * time: 74.24275588989258
    45     1.226088e+03     4.675833e+01
 * time: 75.61262202262878
    46     1.226088e+03     4.628497e+01
 * time: 76.96887493133545
    47     1.226085e+03     4.541356e+01
 * time: 78.32595992088318
    48     1.226080e+03     4.402741e+01
 * time: 79.6824209690094
    49     1.226064e+03     4.142299e+01
 * time: 81.04272484779358
    50     1.226026e+03     3.663064e+01
 * time: 82.41365385055542
    51     1.225931e+03     2.851375e+01
 * time: 83.77667593955994
    52     1.225713e+03     2.844436e+01
 * time: 85.19013500213623
    53     1.225303e+03     3.026440e+01
 * time: 86.57701802253723
    54     1.224791e+03     4.157127e+01
 * time: 87.94020295143127
    55     1.224489e+03     5.047474e+01
 * time: 89.31216096878052
    56     1.224420e+03     4.451064e+01
 * time: 90.74336194992065
    57     1.224413e+03     3.994026e+01
 * time: 92.09214901924133
    58     1.224412e+03     3.879446e+01
 * time: 93.44346594810486
    59     1.224408e+03     3.677250e+01
 * time: 94.80109596252441
    60     1.224400e+03     3.377993e+01
 * time: 96.1508629322052
    61     1.224379e+03     3.158187e+01
 * time: 97.52853894233704
    62     1.224324e+03     2.925155e+01
 * time: 98.8903980255127
    63     1.224180e+03     2.815886e+01
 * time: 100.25663805007935
    64     1.223813e+03     2.818297e+01
 * time: 101.62795686721802
    65     1.222906e+03     4.598758e+01
 * time: 103.03600597381592
    66     1.220910e+03     8.692142e+01
 * time: 104.40268206596375
    67     1.217609e+03     1.136529e+02
 * time: 105.77456092834473
    68     1.214313e+03     9.030271e+01
 * time: 107.12677597999573
    69     1.212533e+03     8.868947e+01
 * time: 108.51322889328003
    70     1.212272e+03     8.970279e+01
 * time: 109.87358784675598
    71     1.212264e+03     8.921922e+01
 * time: 111.22936296463013
    72     1.212259e+03     8.882366e+01
 * time: 112.58034586906433
    73     1.212242e+03     8.761509e+01
 * time: 113.92434787750244
    74     1.212205e+03     8.561995e+01
 * time: 115.25925087928772
    75     1.212103e+03     8.125315e+01
 * time: 116.57272100448608
    76     1.211850e+03     7.229633e+01
 * time: 117.8692479133606
    77     1.211238e+03     5.321838e+01
 * time: 119.19737792015076
    78     1.209945e+03     7.377546e+01
 * time: 120.49001383781433
    79     1.207890e+03     8.404092e+01
 * time: 121.82098293304443
    80     1.206058e+03     9.148114e+01
 * time: 123.1292769908905
    81     1.205389e+03     9.689402e+01
 * time: 124.40561604499817
    82     1.205303e+03     8.594692e+01
 * time: 125.70369505882263
    83     1.205297e+03     8.262969e+01
 * time: 126.99411392211914
    84     1.205293e+03     8.096366e+01
 * time: 128.2679100036621
    85     1.205277e+03     7.747618e+01
 * time: 129.56158185005188
    86     1.205241e+03     7.259258e+01
 * time: 130.8484559059143
    87     1.205143e+03     6.664833e+01
 * time: 132.1497540473938
    88     1.204895e+03     6.374646e+01
 * time: 133.49039387702942
    89     1.204268e+03     5.753767e+01
 * time: 134.84536290168762
    90     1.202818e+03     4.866322e+01
 * time: 136.17918395996094
    91     1.200116e+03     5.085841e+01
 * time: 137.4999668598175
    92     1.196895e+03     7.139477e+01
 * time: 138.83528184890747
    93     1.194610e+03     4.693642e+01
 * time: 140.16371488571167
    94     1.193880e+03     4.874637e+01
 * time: 141.5410978794098
    95     1.193833e+03     4.997341e+01
 * time: 142.8707640171051
    96     1.193831e+03     5.008752e+01
 * time: 144.2117109298706
    97     1.193829e+03     5.014860e+01
 * time: 145.62985587120056
    98     1.193824e+03     5.025195e+01
 * time: 147.03822684288025
    99     1.193812e+03     5.040245e+01
 * time: 148.44854187965393
   100     1.193778e+03     5.061928e+01
 * time: 149.8715488910675
   101     1.193693e+03     5.087910e+01
 * time: 151.29440999031067
   102     1.193472e+03     5.105104e+01
 * time: 152.64622688293457
   103     1.192926e+03     5.068579e+01
 * time: 153.9582118988037
   104     1.191681e+03     4.863476e+01
 * time: 155.22451186180115
   105     1.189351e+03     4.892982e+01
 * time: 156.47253489494324
   106     1.186420e+03     7.777398e+01
 * time: 157.7377049922943
   107     1.184527e+03     8.874390e+01
 * time: 158.99657487869263
   108     1.184034e+03     8.377339e+01
 * time: 160.26790690422058
   109     1.183978e+03     7.932702e+01
 * time: 161.5211079120636
   110     1.183969e+03     7.794331e+01
 * time: 162.77012705802917
   111     1.183966e+03     7.787273e+01
 * time: 164.0265028476715
   112     1.183962e+03     7.833691e+01
 * time: 165.33348989486694
   113     1.183955e+03     7.929110e+01
 * time: 166.65898990631104
   114     1.183940e+03     8.084135e+01
 * time: 167.98653388023376
   115     1.183904e+03     8.331062e+01
 * time: 169.27821493148804
   116     1.183812e+03     8.698431e+01
 * time: 170.5929639339447
   117     1.183576e+03     9.188953e+01
 * time: 171.95075392723083
   118     1.182997e+03     9.668921e+01
 * time: 173.3104648590088
   119     1.181702e+03     9.635659e+01
 * time: 174.66923999786377
   120     1.179436e+03     8.061098e+01
 * time: 176.04682183265686
   121     1.177026e+03     4.571918e+01
 * time: 177.44839096069336
   122     1.175794e+03     1.863482e+01
 * time: 178.88221788406372
   123     1.175474e+03     1.968114e+01
 * time: 180.25503396987915
   124     1.175429e+03     1.958620e+01
 * time: 181.59373784065247
   125     1.175427e+03     1.993702e+01
 * time: 183.041002035141
   126     1.175426e+03     1.962020e+01
 * time: 184.42174696922302
   127     1.175426e+03     1.965822e+01
 * time: 185.77183604240417
   128     1.175424e+03     1.984458e+01
 * time: 187.16407585144043
   129     1.175421e+03     2.001151e+01
 * time: 188.5387978553772
   130     1.175413e+03     2.035203e+01
 * time: 189.9340078830719
   131     1.175392e+03     2.084295e+01
 * time: 191.32540798187256
   132     1.175336e+03     2.164587e+01
 * time: 192.70958995819092
   133     1.175189e+03     2.287862e+01
 * time: 194.05450201034546
   134     1.174801e+03     2.475388e+01
 * time: 195.38134384155273
   135     1.173792e+03     4.143552e+01
 * time: 196.71206498146057
   136     1.171220e+03     7.151629e+01
 * time: 198.07408094406128
   137     1.165144e+03     1.078851e+02
 * time: 199.5346188545227
   138     1.155079e+03     7.750603e+01
 * time: 201.10307598114014
   139     1.149212e+03     6.869378e+01
 * time: 202.70089983940125
   140     1.146920e+03     6.357052e+01
 * time: 204.32509899139404
   141     1.144663e+03     4.948266e+01
 * time: 205.94313097000122
   142     1.143084e+03     2.539126e+01
 * time: 207.44376301765442
   143     1.141829e+03     1.979229e+01
 * time: 208.8740930557251
   144     1.141293e+03     2.050881e+01
 * time: 210.38423895835876
   145     1.141052e+03     2.076835e+01
 * time: 211.83070588111877
   146     1.140979e+03     2.090550e+01
 * time: 213.26495504379272
   147     1.140976e+03     2.094541e+01
 * time: 214.67772793769836
   148     1.140975e+03     2.099654e+01
 * time: 216.10724592208862
   149     1.140974e+03     2.099916e+01
 * time: 217.57909893989563
   150     1.140974e+03     2.099880e+01
 * time: 219.03184604644775
   151     1.140973e+03     2.099210e+01
 * time: 220.53654289245605
   152     1.140972e+03     2.098163e+01
 * time: 222.0392780303955
   153     1.140970e+03     2.096557e+01
 * time: 223.5425808429718
   154     1.140963e+03     2.094347e+01
 * time: 225.09362387657166
   155     1.140947e+03     2.091734e+01
 * time: 226.66516304016113
   156     1.140905e+03     2.089968e+01
 * time: 228.26662492752075
   157     1.140795e+03     2.093513e+01
 * time: 229.84285187721252
   158     1.140505e+03     2.116003e+01
 * time: 231.38762092590332
   159     1.139717e+03     2.228845e+01
 * time: 232.948224067688
   160     1.137490e+03     3.499275e+01
 * time: 234.59126806259155
   161     1.132263e+03     6.112003e+01
 * time: 236.28288888931274
   162     1.129968e+03     7.040706e+01
 * time: 238.39471101760864
   163     1.128183e+03     7.684081e+01
 * time: 240.6832139492035
   164     1.125121e+03     1.651402e+02
 * time: 242.86091995239258
   165     1.124367e+03     1.524469e+02
 * time: 244.81681895256042
   166     1.117089e+03     4.431295e+01
 * time: 246.7511019706726
   167     1.113092e+03     1.609702e+01
 * time: 248.7464849948883
   168     1.111588e+03     1.011714e+01
 * time: 250.70158100128174
   169     1.111231e+03     1.280570e+01
 * time: 252.61687397956848
   170     1.111200e+03     1.186560e+01
 * time: 254.48356986045837
   171     1.111188e+03     1.091436e+01
 * time: 256.39161586761475
   172     1.111187e+03     1.052729e+01
 * time: 258.21701288223267
   173     1.111187e+03     1.067420e+01
 * time: 260.07829689979553
   174     1.111187e+03     1.055472e+01
 * time: 261.97083806991577
   175     1.111187e+03     1.036659e+01
 * time: 263.8777709007263
   176     1.111185e+03     1.017962e+01
 * time: 265.8946440219879
   177     1.111183e+03     1.017379e+01
 * time: 267.8660509586334
   178     1.111176e+03     1.016131e+01
 * time: 269.82666397094727
   179     1.111157e+03     1.013351e+01
 * time: 271.78626585006714
   180     1.111109e+03     1.006842e+01
 * time: 273.73224401474
   181     1.110986e+03     1.142083e+01
 * time: 275.63618898391724
   182     1.110675e+03     1.751466e+01
 * time: 277.5228068828583
   183     1.109918e+03     2.591233e+01
 * time: 279.4431529045105
   184     1.108234e+03     3.515773e+01
 * time: 281.4320569038391
   185     1.105216e+03     3.902425e+01
 * time: 283.41052293777466
   186     1.101588e+03     3.080377e+01
 * time: 285.3537268638611
   187     1.098345e+03     3.607134e+01
 * time: 287.35308599472046
   188     1.094148e+03     3.626407e+01
 * time: 289.42933106422424
   189     1.093478e+03     3.314569e+01
 * time: 291.7464950084686
   190     1.092996e+03     2.938811e+01
 * time: 294.1085638999939
   191     1.092406e+03     2.138312e+01
 * time: 296.55131793022156
   192     1.092297e+03     2.975339e+01
 * time: 298.87501883506775
   193     1.091949e+03     7.639324e+00
 * time: 301.11450004577637
   194     1.091909e+03     4.276154e+00
 * time: 303.3737909793854
   195     1.091904e+03     4.346069e+00
 * time: 305.6366620063782
   196     1.091904e+03     4.337170e+00
 * time: 307.8746359348297
   197     1.091904e+03     4.342274e+00
 * time: 310.1256539821625
   198     1.091904e+03     4.344184e+00
 * time: 312.3570020198822
   199     1.091904e+03     4.346951e+00
 * time: 314.59187483787537
   200     1.091904e+03     4.349040e+00
 * time: 316.83250188827515
   201     1.091904e+03     4.348757e+00
 * time: 319.0764379501343
   202     1.091904e+03     4.343922e+00
 * time: 321.3279929161072
   203     1.091903e+03     4.333452e+00
 * time: 323.57368683815
   204     1.091902e+03     4.317872e+00
 * time: 325.8067078590393
   205     1.091901e+03     4.295486e+00
 * time: 328.03695583343506
   206     1.091897e+03     4.261316e+00
 * time: 330.2564649581909
   207     1.091889e+03     5.125139e+00
 * time: 332.51975083351135
   208     1.091867e+03     9.013047e+00
 * time: 335.7650909423828
   209     1.091811e+03     1.513012e+01
 * time: 338.71681904792786
   210     1.091668e+03     2.427311e+01
 * time: 341.3882648944855
   211     1.091325e+03     3.642351e+01
 * time: 343.70767188072205
   212     1.090580e+03     4.801992e+01
 * time: 346.15532398223877
   213     1.089340e+03     5.062255e+01
 * time: 348.5607559680939
   214     1.088109e+03     4.437004e+01
 * time: 350.8699269294739
   215     1.087458e+03     3.115088e+01
 * time: 353.07188391685486
   216     1.087119e+03     1.183083e+01
 * time: 355.26864194869995
   217     1.087046e+03     5.394070e+00
 * time: 357.46981596946716
   218     1.087043e+03     5.390830e+00
 * time: 359.64521884918213
   219     1.087043e+03     5.383737e+00
 * time: 361.888552904129
   220     1.087043e+03     5.384236e+00
 * time: 364.52495884895325
   221     1.087043e+03     5.384636e+00
 * time: 366.9340159893036
   222     1.087043e+03     5.385864e+00
 * time: 369.1040370464325
   223     1.087043e+03     5.387179e+00
 * time: 371.28600883483887
   224     1.087042e+03     5.389948e+00
 * time: 373.53688406944275
   225     1.087041e+03     5.395184e+00
 * time: 375.70870995521545
   226     1.087039e+03     5.407029e+00
 * time: 377.9040639400482
   227     1.087033e+03     5.434556e+00
 * time: 380.13645601272583
   228     1.087016e+03     5.502571e+00
 * time: 382.36235785484314
   229     1.086972e+03     5.677167e+00
 * time: 384.5774199962616
   230     1.086849e+03     8.425733e+00
 * time: 386.8095920085907
   231     1.086459e+03     1.475408e+01
 * time: 389.0079228878021
   232     1.086446e+03     4.299557e+01
 * time: 391.10253500938416
   233     1.085092e+03     2.387717e+01
 * time: 393.2545289993286
   234     1.083538e+03     2.726422e+01
 * time: 395.3614890575409
   235     1.081685e+03     2.845459e+01
 * time: 397.4341070652008
   236     1.080396e+03     2.805425e+01
 * time: 399.6169328689575
   237     1.077803e+03     2.873905e+01
 * time: 401.59939193725586
   238     1.073139e+03     2.780340e+01
 * time: 403.61367297172546
   239     1.069921e+03     1.583445e+01
 * time: 405.68462586402893
   240     1.069621e+03     7.856085e+00
 * time: 407.71548295021057
   241     1.069531e+03     2.311783e+00
 * time: 409.7601869106293
   242     1.069509e+03     2.021453e+00
 * time: 411.8024249076843
   243     1.069491e+03     2.157500e+00
 * time: 413.86292600631714
   244     1.069488e+03     2.225422e+00
 * time: 415.91369700431824
   245     1.069488e+03     2.236782e+00
 * time: 417.9519028663635
   246     1.069488e+03     2.235390e+00
 * time: 419.98416805267334
   247     1.069488e+03     2.235490e+00
 * time: 422.0035319328308
   248     1.069488e+03     2.235491e+00
 * time: 424.1308250427246
   249     1.069488e+03     2.235259e+00
 * time: 426.1524498462677
   250     1.069488e+03     2.235150e+00
 * time: 428.1738200187683
   251     1.069488e+03     2.234587e+00
 * time: 430.2406680583954
   252     1.069487e+03     2.233171e+00
 * time: 432.2974829673767
   253     1.069486e+03     2.229015e+00
 * time: 434.35016894340515
   254     1.069484e+03     2.218016e+00
 * time: 436.41360998153687
   255     1.069477e+03     2.188614e+00
 * time: 438.4706959724426
   256     1.069460e+03     2.790832e+00
 * time: 440.52958583831787
   257     1.069418e+03     4.259790e+00
 * time: 442.59208393096924
   258     1.069326e+03     5.893844e+00
 * time: 444.66876792907715
   259     1.069168e+03     6.471844e+00
 * time: 446.62949991226196
   260     1.069008e+03     4.528747e+00
 * time: 448.6796419620514
   261     1.068940e+03     1.710450e+00
 * time: 450.71741795539856
   262     1.068930e+03     8.661473e-01
 * time: 452.80285000801086
   263     1.068929e+03     8.687543e-01
 * time: 454.8346788883209
   264     1.068929e+03     8.689456e-01
 * time: 456.8873689174652
FittedPumasModel

Dynamical system type:               Nonlinear ODE
Solver(s): (OrdinaryDiffEqVerner.Vern7,OrdinaryDiffEqRosenbrock.Rodas5P)

Number of subjects:                             32

Observation records:         Active        Missing
    conc:                       251             47
    pca:                        232             66
    Total:                      483            113

Number of parameters:      Constant      Optimized
                                  0             18

Likelihood approximation:                     FOCE
Likelihood optimizer:                         BFGS

Termination Reason:                      NoXChange
Log-likelihood value:                   -1068.9294

------------------------
            Estimate
------------------------
pop_CL       0.13521
pop_V        8.0112
pop_tabs     0.56615
pop_lag      0.87614
pop_e0      96.395
pop_emax    -1.0613
pop_c50      1.4884
pop_tover   14.053
pk_Ω₁,₁      0.06929
pk_Ω₂,₂      0.020318
pk_Ω₃,₃      0.89963
pd_Ω₁,₁      0.0028776
pd_Ω₂,₂      0.00044803
pd_Ω₃,₃      0.15375
pd_Ω₄,₄      0.015014
σ_prop       0.088936
σ_add        0.41486
σ_fx         3.5814
------------------------
Tip

It is not recommended to decrease tolerances below 1e-14.

7.1 Changing the Algorithm

Usually, it should not be necessary to adjust the differential equation solver. If you change the solver, you should follow the guidelines in the SciML documentation that explains which solvers are the most efficient at the desired tolerance level.

For instance, if it is known that a differential equation is stiff, a stiff solver such as Rosenbrock23 at high tolerances or Rodas5P at low tolerances could be a possible alternative to the default auto-switching solver:

# Fitting with stiff solver Rodas5P at low tolerances (relative: 1e-8, absolute: 1e-12)
fit(
    warfarin_pkpd_model,
    pop,
    init_params(warfarin_pkpd_model),
    FOCE();
    diffeq_options = (; alg = Rodas5P(), reltol = 1e-8, abstol = 1e-12),
)
[ Info: Checking the initial parameter values.
[ Info: The initial negative log likelihood and its gradient are finite. Check passed.
Iter     Function value   Gradient norm 
     0     3.125741e+06     5.911803e+06
 * time: 3.0994415283203125e-5
     1     5.174461e+05     8.708699e+05
 * time: 10.08549189567566
     2     3.865265e+05     6.344302e+05
 * time: 18.191150903701782
     3     1.804274e+05     2.829723e+05
 * time: 26.057904958724976
     4     9.706641e+04     1.550547e+05
 * time: 34.09296798706055
     5     4.769637e+04     6.778818e+04
 * time: 42.12146806716919
     6     2.902319e+04     3.499747e+04
 * time: 50.21349096298218
     7     1.823472e+04     1.705751e+04
 * time: 57.94804787635803
     8     1.258819e+04     9.569382e+03
 * time: 65.69003200531006
     9     9.389985e+03     8.615853e+03
 * time: 73.36286687850952
    10     7.314703e+03     7.636886e+03
 * time: 80.92074704170227
    11     5.916030e+03     6.624328e+03
 * time: 88.43818092346191
    12     4.930520e+03     5.558143e+03
 * time: 95.92720603942871
    13     4.125062e+03     4.315761e+03
 * time: 104.45348691940308
    14     3.549280e+03     3.051094e+03
 * time: 112.81527400016785
    15     3.283490e+03     2.157293e+03
 * time: 120.09153389930725
    16     3.204886e+03     1.659798e+03
 * time: 127.57366108894348
    17     3.194875e+03     1.480528e+03
 * time: 135.08616495132446
    18     3.193944e+03     1.437922e+03
 * time: 142.59069108963013
    19     3.193070e+03     1.411186e+03
 * time: 149.92508792877197
    20     3.190129e+03     1.355327e+03
 * time: 157.59825587272644
    21     3.183228e+03     1.276603e+03
 * time: 165.28803896903992
    22     3.164897e+03     1.151838e+03
 * time: 173.19753289222717
    23     3.119250e+03     9.712652e+02
 * time: 182.10435605049133
    24     3.006297e+03     7.204344e+02
 * time: 190.0906000137329
    25     2.738913e+03     4.050546e+02
 * time: 197.79244709014893
    26     2.123834e+03     2.318194e+02
 * time: 205.34040999412537
    27     1.789142e+03     2.290466e+02
 * time: 213.61461091041565
    28     1.396456e+03     1.683975e+02
 * time: 230.96926093101501
    29     1.333545e+03     1.336198e+02
 * time: 240.36588501930237
    30     1.297773e+03     2.452181e+02
 * time: 247.83066201210022
    31     1.266002e+03     1.523972e+02
 * time: 255.29916787147522
    32     1.255505e+03     1.734000e+02
 * time: 262.897696018219
    33     1.247788e+03     1.971637e+02
 * time: 270.64445090293884
    34     1.244490e+03     1.915744e+02
 * time: 278.2859649658203
    35     1.240568e+03     1.704280e+02
 * time: 285.8861758708954
    36     1.240502e+03     1.711813e+02
 * time: 293.3388168811798
    37     1.240491e+03     1.711683e+02
 * time: 300.796128988266
    38     1.239992e+03     1.687296e+02
 * time: 308.377436876297
    39     1.239200e+03     1.624744e+02
 * time: 316.07769894599915
    40     1.236975e+03     1.400443e+02
 * time: 323.73160099983215
    41     1.233209e+03     9.449763e+01
 * time: 333.49364709854126
    42     1.228687e+03     3.276923e+01
 * time: 341.31556391716003
    43     1.226467e+03     4.997214e+01
 * time: 348.94008588790894
    44     1.226104e+03     4.905105e+01
 * time: 356.6202130317688
    45     1.226088e+03     4.676122e+01
 * time: 364.2222430706024
    46     1.226087e+03     4.628674e+01
 * time: 371.62658405303955
    47     1.226085e+03     4.541753e+01
 * time: 379.11325907707214
    48     1.226080e+03     4.403288e+01
 * time: 386.51107597351074
    49     1.226064e+03     4.143315e+01
 * time: 394.0518629550934
    50     1.226026e+03     3.664876e+01
 * time: 401.6194040775299
    51     1.225931e+03     2.851383e+01
 * time: 409.1823420524597
    52     1.225714e+03     2.844460e+01
 * time: 418.55847096443176
    53     1.225304e+03     3.025732e+01
 * time: 427.0618488788605
    54     1.224793e+03     4.151448e+01
 * time: 434.8933370113373
    55     1.224489e+03     5.047755e+01
 * time: 442.6357419490814
    56     1.224420e+03     4.452753e+01
 * time: 450.3093030452728
    57     1.224413e+03     3.994380e+01
 * time: 457.8525040149689
    58     1.224412e+03     3.879465e+01
 * time: 465.3744649887085
    59     1.224408e+03     3.677922e+01
 * time: 472.9092769622803
    60     1.224400e+03     3.379126e+01
 * time: 480.3521909713745
    61     1.224379e+03     3.158821e+01
 * time: 487.8674170970917
    62     1.224324e+03     2.926306e+01
 * time: 495.3346300125122
    63     1.224181e+03     2.815869e+01
 * time: 502.81563997268677
    64     1.223815e+03     2.818300e+01
 * time: 510.3729269504547
    65     1.222911e+03     4.583041e+01
 * time: 517.923749923706
    66     1.220921e+03     8.675281e+01
 * time: 525.4331960678101
    67     1.217625e+03     1.136294e+02
 * time: 532.9681289196014
    68     1.214324e+03     9.050244e+01
 * time: 540.432126045227
    69     1.212536e+03     8.867180e+01
 * time: 547.8575918674469
    70     1.212272e+03     8.970655e+01
 * time: 555.2410318851471
    71     1.212263e+03     8.922293e+01
 * time: 562.5489919185638
    72     1.212259e+03     8.882951e+01
 * time: 569.8617570400238
    73     1.212242e+03     8.761908e+01
 * time: 577.1773819923401
    74     1.212205e+03     8.562573e+01
 * time: 584.5113599300385
    75     1.212102e+03     8.125881e+01
 * time: 591.9010560512543
    76     1.211850e+03     7.230599e+01
 * time: 599.3711540699005
    77     1.211238e+03     5.323492e+01
 * time: 606.7648060321808
    78     1.209946e+03     7.373618e+01
 * time: 614.2040779590607
    79     1.207891e+03     8.401772e+01
 * time: 621.5980889797211
    80     1.206059e+03     9.146801e+01
 * time: 630.1043679714203
    81     1.205389e+03     9.690592e+01
 * time: 637.5221469402313
    82     1.205302e+03     8.595286e+01
 * time: 644.908117055893
    83     1.205296e+03     8.263040e+01
 * time: 652.1829519271851
    84     1.205292e+03     8.096547e+01
 * time: 659.593190908432
    85     1.205276e+03     7.747632e+01
 * time: 666.9177839756012
    86     1.205240e+03     7.259211e+01
 * time: 674.340658903122
    87     1.205143e+03     6.664635e+01
 * time: 681.7046210765839
    88     1.204894e+03     6.374389e+01
 * time: 689.219358921051
    89     1.204267e+03     5.753484e+01
 * time: 696.5747950077057
    90     1.202818e+03     4.869938e+01
 * time: 703.9712300300598
    91     1.200117e+03     5.087313e+01
 * time: 711.3690550327301
    92     1.196896e+03     7.141162e+01
 * time: 718.7447528839111
    93     1.194612e+03     4.695316e+01
 * time: 726.0801439285278
    94     1.193881e+03     4.874366e+01
 * time: 733.4677369594574
    95     1.193834e+03     4.997038e+01
 * time: 740.7661969661713
    96     1.193832e+03     5.008442e+01
 * time: 747.9423789978027
    97     1.193830e+03     5.014549e+01
 * time: 755.1373920440674
    98     1.193825e+03     5.024884e+01
 * time: 765.5117809772491
    99     1.193813e+03     5.039938e+01
 * time: 772.9342908859253
   100     1.193779e+03     5.061632e+01
 * time: 780.0720548629761
   101     1.193694e+03     5.087641e+01
 * time: 787.2071130275726
   102     1.193473e+03     5.104895e+01
 * time: 794.3223650455475
   103     1.192927e+03     5.068500e+01
 * time: 801.4699790477753
   104     1.191682e+03     4.863684e+01
 * time: 808.5548150539398
   105     1.189353e+03     4.890365e+01
 * time: 815.4794020652771
   106     1.186424e+03     7.778082e+01
 * time: 822.5067028999329
   107     1.184533e+03     8.873607e+01
 * time: 829.4352869987488
   108     1.184042e+03     8.376145e+01
 * time: 836.4146299362183
   109     1.183986e+03     7.931813e+01
 * time: 843.435338973999
   110     1.183978e+03     7.793645e+01
 * time: 850.5612668991089
   111     1.183974e+03     7.786675e+01
 * time: 858.3795380592346
   112     1.183970e+03     7.833168e+01
 * time: 865.5764429569244
   113     1.183963e+03     7.928653e+01
 * time: 872.7332870960236
   114     1.183949e+03     8.083870e+01
 * time: 879.8570690155029
   115     1.183913e+03     8.331100e+01
 * time: 887.1313829421997
   116     1.183820e+03     8.698958e+01
 * time: 894.4087228775024
   117     1.183584e+03     9.190093e+01
 * time: 903.6383080482483
   118     1.183003e+03     9.670514e+01
 * time: 910.9472780227661
   119     1.181706e+03     9.636548e+01
 * time: 918.2859179973602
   120     1.179435e+03     8.059042e+01
 * time: 925.5823578834534
   121     1.177024e+03     4.567337e+01
 * time: 932.9123959541321
   122     1.175793e+03     1.863452e+01
 * time: 940.3037650585175
   123     1.175474e+03     1.967979e+01
 * time: 947.5520920753479
   124     1.175430e+03     1.958939e+01
 * time: 954.8643209934235
   125     1.175427e+03     1.993415e+01
 * time: 962.1931190490723
   126     1.175427e+03     1.962015e+01
 * time: 969.4152438640594
   127     1.175426e+03     1.965822e+01
 * time: 976.5550479888916
   128     1.175424e+03     1.984190e+01
 * time: 983.8179590702057
   129     1.175422e+03     2.000843e+01
 * time: 991.1798169612885
   130     1.175413e+03     2.034664e+01
 * time: 998.3535859584808
   131     1.175392e+03     2.083524e+01
 * time: 1005.4594168663025
   132     1.175336e+03     2.163395e+01
 * time: 1012.8585200309753
   133     1.175190e+03     2.286075e+01
 * time: 1020.8742668628693
   134     1.174803e+03     2.472708e+01
 * time: 1028.3417830467224
   135     1.173797e+03     4.124367e+01
 * time: 1035.883635044098
   136     1.171232e+03     7.123154e+01
 * time: 1043.5812079906464
   137     1.165167e+03     1.075848e+02
 * time: 1051.492215871811
   138     1.155096e+03     7.751300e+01
 * time: 1059.4278349876404
   139     1.149210e+03     6.815707e+01
 * time: 1067.51943898201
   140     1.146904e+03     6.218499e+01
 * time: 1075.4210000038147
   141     1.144688e+03     5.158716e+01
 * time: 1083.3619079589844
   142     1.143100e+03     2.555104e+01
 * time: 1091.3381559848785
   143     1.141816e+03     1.970245e+01
 * time: 1099.2035639286041
   144     1.141294e+03     2.048648e+01
 * time: 1108.420124053955
   145     1.141044e+03     2.076701e+01
 * time: 1116.7233469486237
   146     1.140979e+03     2.090339e+01
 * time: 1124.4975650310516
   147     1.140976e+03     2.094515e+01
 * time: 1132.246516942978
   148     1.140975e+03     2.099576e+01
 * time: 1140.047329902649
   149     1.140974e+03     2.099888e+01
 * time: 1147.8510870933533
   150     1.140974e+03     2.099931e+01
 * time: 1155.7224719524384
   151     1.140973e+03     2.099295e+01
 * time: 1163.7300870418549
   152     1.140972e+03     2.098305e+01
 * time: 1171.5957670211792
   153     1.140970e+03     2.096756e+01
 * time: 1179.4612119197845
   154     1.140963e+03     2.094619e+01
 * time: 1187.4338519573212
   155     1.140947e+03     2.092087e+01
 * time: 1195.2383868694305
   156     1.140906e+03     2.090400e+01
 * time: 1202.9390060901642
   157     1.140797e+03     2.093964e+01
 * time: 1210.8675019741058
   158     1.140511e+03     2.116231e+01
 * time: 1219.024020910263
   159     1.139732e+03     2.193009e+01
 * time: 1227.0754880905151
   160     1.137531e+03     3.209812e+01
 * time: 1235.1209509372711
   161     1.132353e+03     5.451900e+01
 * time: 1243.2788889408112
   162     1.130098e+03     6.354058e+01
 * time: 1251.7811479568481
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
   163     1.128599e+03     6.862520e+01
 * time: 1260.6219720840454
   164     1.127623e+03     8.385757e+01
 * time: 1269.4574558734894
   165     1.122228e+03     1.204824e+02
 * time: 1277.8529529571533
   166     1.118774e+03     1.225695e+02
 * time: 1286.062891960144
   167     1.115679e+03     4.611268e+01
 * time: 1294.1571969985962
   168     1.113979e+03     3.434831e+01
 * time: 1302.3025388717651
   169     1.112521e+03     3.523199e+01
 * time: 1310.587739944458
   170     1.111267e+03     1.228403e+01
 * time: 1318.7387800216675
   171     1.111189e+03     1.078353e+01
 * time: 1326.9373590946198
   172     1.111187e+03     1.048242e+01
 * time: 1335.3299369812012
   173     1.111187e+03     1.070654e+01
 * time: 1345.7729210853577
   174     1.111187e+03     1.057812e+01
 * time: 1353.7987558841705
   175     1.111187e+03     1.055136e+01
 * time: 1361.8972699642181
   176     1.111186e+03     1.049712e+01
 * time: 1370.0765290260315
   177     1.111185e+03     1.042508e+01
 * time: 1379.687306880951
   178     1.111181e+03     1.030463e+01
 * time: 1387.9390530586243
   179     1.111173e+03     1.018028e+01
 * time: 1396.2664229869843
   180     1.111150e+03     1.017084e+01
 * time: 1404.479413986206
   181     1.111091e+03     1.547976e+01
 * time: 1412.65838098526
   182     1.110938e+03     2.528645e+01
 * time: 1420.8021450042725
   183     1.110546e+03     4.010028e+01
 * time: 1428.996183872223
   184     1.109576e+03     6.035708e+01
 * time: 1437.0932619571686
   185     1.107416e+03     8.168777e+01
 * time: 1445.2246930599213
   186     1.103899e+03     9.586365e+01
 * time: 1453.3344569206238
   187     1.100518e+03     1.082019e+02
 * time: 1461.4210278987885
   188     1.096703e+03     1.051881e+02
 * time: 1469.6246409416199
   189     1.092614e+03     3.371950e+01
 * time: 1478.0849659442902
   190     1.092108e+03     2.854225e+01
 * time: 1486.5472779273987
   191     1.091924e+03     8.267155e+00
 * time: 1498.0392289161682
   192     1.091910e+03     4.388021e+00
 * time: 1506.301176071167
   193     1.091908e+03     4.381246e+00
 * time: 1514.5959470272064
   194     1.091906e+03     4.351855e+00
 * time: 1523.017145872116
   195     1.091905e+03     4.347981e+00
 * time: 1531.4109258651733
   196     1.091904e+03     4.344942e+00
 * time: 1539.6831409931183
   197     1.091904e+03     4.343567e+00
 * time: 1547.753278017044
   198     1.091904e+03     4.341811e+00
 * time: 1555.9967720508575
   199     1.091904e+03     4.338160e+00
 * time: 1564.1387119293213
   200     1.091904e+03     4.331286e+00
 * time: 1572.2593879699707
   201     1.091904e+03     4.319913e+00
 * time: 1580.3326919078827
   202     1.091903e+03     4.299872e+00
 * time: 1588.4866309165955
   203     1.091901e+03     4.267805e+00
 * time: 1597.5446979999542
   204     1.091897e+03     4.211166e+00
 * time: 1605.81454205513
   205     1.091886e+03     4.118011e+00
 * time: 1616.958899974823
   206     1.091856e+03     4.884541e+00
 * time: 1625.9775259494781
   207     1.091780e+03     7.435767e+00
 * time: 1634.2627580165863
   208     1.091587e+03     1.171416e+01
 * time: 1642.5469369888306
   209     1.091126e+03     1.720748e+01
 * time: 1650.9167029857635
   210     1.090066e+03     2.180540e+01
 * time: 1659.2485930919647
   211     1.088566e+03     2.176055e+01
 * time: 1667.6395409107208
   212     1.087529e+03     2.216379e+01
 * time: 1677.723247051239
   213     1.087131e+03     6.871069e+00
 * time: 1688.5370450019836
   214     1.087053e+03     5.487618e+00
 * time: 1703.0826480388641
   215     1.087044e+03     5.346767e+00
 * time: 1715.1214179992676
   216     1.087043e+03     5.364351e+00
 * time: 1727.4196119308472
   217     1.087043e+03     5.380873e+00
 * time: 1737.2756400108337
   218     1.087043e+03     5.385017e+00
 * time: 1748.9424018859863
   219     1.087043e+03     5.387076e+00
 * time: 1760.6793599128723
   220     1.087043e+03     5.393037e+00
 * time: 1770.4370019435883
   221     1.087043e+03     5.401737e+00
 * time: 1780.3918149471283
   222     1.087042e+03     5.417220e+00
 * time: 1792.3762118816376
   223     1.087041e+03     5.443370e+00
 * time: 1801.5814599990845
   224     1.087039e+03     5.489836e+00
 * time: 1810.3141560554504
   225     1.087032e+03     5.575602e+00
 * time: 1822.68763589859
   226     1.087015e+03     5.744360e+00
 * time: 1833.023402929306
   227     1.086967e+03     8.458307e+00
 * time: 1841.150279045105
   228     1.086833e+03     1.434823e+01
 * time: 1849.2932028770447
   229     1.086295e+03     2.779692e+01
 * time: 1857.9522750377655
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: First function call produced NaNs. Exiting. Double check that none of the initial conditions, parameters, or timespan values are NaN.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/initdt.jl:253
Warning: Automatic dt set the starting dt as NaN, causing instability. Exiting.
@ OrdinaryDiffEqCore ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/OrdinaryDiffEqCore/LG1u6/src/solve.jl:654
Warning: NaN dt detected. Likely a NaN value in the state, parameters, or derivative value caused this outcome.
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:583
Warning: At t=0.4500886809099674, dt was forced below floating point epsilon 5.551115123125783e-17, and step error estimate = 4.8708450078891075e20. Aborting. There is either an error in your model specification or the true solution is unstable (or the true solution can not be represented in the precision of ForwardDiff.Dual{ForwardDiff.Tag{Pumas.Tag, Float64}, Float64, 7}).
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:623
Warning: At t=0.4500886809099674, dt was forced below floating point epsilon 5.551115123125783e-17, and step error estimate = 4.8708450078891075e20. Aborting. There is either an error in your model specification or the true solution is unstable (or the true solution can not be represented in the precision of ForwardDiff.Dual{ForwardDiff.Tag{Pumas.Tag, Float64}, Float64, 7}).
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:623
   230     1.086121e+03     6.179899e+01
 * time: 1868.2224929332733
   231     1.085699e+03     4.269436e+01
 * time: 1876.4216940402985
   232     1.085153e+03     5.101086e+01
 * time: 1884.5097138881683
   233     1.084625e+03     5.803468e+01
 * time: 1892.5904490947723
   234     1.084371e+03     6.244198e+01
 * time: 1901.1619610786438
   235     1.083958e+03     6.785742e+01
 * time: 1909.2674760818481
   236     1.083163e+03     6.963805e+01
 * time: 1917.3103029727936
   237     1.081667e+03     6.332470e+01
 * time: 1925.3473188877106
   238     1.080941e+03     5.916175e+01
 * time: 1933.1295099258423
   239     1.079241e+03     5.431208e+01
 * time: 1940.9890339374542
   240     1.076096e+03     3.465388e+01
 * time: 1951.40802693367
   241     1.072649e+03     1.670281e+01
 * time: 1959.6910519599915
   242     1.069992e+03     1.935661e+01
 * time: 1967.6729390621185
   243     1.069558e+03     3.678375e+00
 * time: 1975.3966999053955
   244     1.069496e+03     2.270102e+00
 * time: 1986.0689570903778
   245     1.069488e+03     2.221349e+00
 * time: 1994.4514379501343
   246     1.069488e+03     2.237998e+00
 * time: 2002.0855770111084
   247     1.069488e+03     2.236062e+00
 * time: 2009.7287380695343
   248     1.069488e+03     2.235507e+00
 * time: 2019.4155640602112
   249     1.069488e+03     2.234690e+00
 * time: 2027.027909040451
   250     1.069488e+03     2.233625e+00
 * time: 2034.334240913391
   251     1.069488e+03     2.231719e+00
 * time: 2041.6176300048828
   252     1.069488e+03     2.228573e+00
 * time: 2048.89395904541
   253     1.069487e+03     2.223013e+00
 * time: 2056.1925899982452
   254     1.069487e+03     2.212970e+00
 * time: 2063.4897220134735
   255     1.069485e+03     2.193875e+00
 * time: 2070.8365230560303
   256     1.069481e+03     2.558103e+00
 * time: 2078.186975955963
   257     1.069470e+03     4.099866e+00
 * time: 2085.768434047699
   258     1.069441e+03     6.445399e+00
 * time: 2093.7621150016785
   259     1.069374e+03     9.551161e+00
 * time: 2100.850672006607
   260     1.069241e+03     1.204286e+01
 * time: 2107.8825080394745
   261     1.069065e+03     1.050115e+01
 * time: 2115.268637895584
   262     1.068958e+03     5.184001e+00
 * time: 2122.4012138843536
   263     1.068932e+03     1.288840e+00
 * time: 2129.3792209625244
   264     1.068929e+03     8.682448e-01
 * time: 2136.677870988846
   265     1.068929e+03     8.688495e-01
 * time: 2143.8077199459076
   266     1.068929e+03     8.688500e-01
 * time: 2151.2941660881042
   267     1.068929e+03     8.689152e-01
 * time: 2158.743479013443
   268     1.068929e+03     8.689157e-01
 * time: 2166.0727310180664
   269     1.068929e+03     8.690133e-01
 * time: 2173.9399960041046
   270     1.068929e+03     8.690133e-01
 * time: 2183.5664670467377
   271     1.068929e+03     8.693257e-01
 * time: 2193.099380970001
   272     1.068929e+03     8.693100e-01
 * time: 2201.1834840774536
   273     1.068919e+03     9.277276e-01
 * time: 2208.997227907181
   274     1.068907e+03     1.626480e+00
 * time: 2216.510533094406
   275     1.068835e+03     4.106347e+00
 * time: 2223.9146480560303
   276     1.068726e+03     6.157731e+00
 * time: 2231.6306250095367
   277     1.068548e+03     7.201969e+00
 * time: 2239.875617980957
   278     1.068415e+03     5.646200e+00
 * time: 2247.4018890857697
   279     1.068386e+03     3.803550e+00
 * time: 2254.8616259098053
   280     1.068384e+03     3.184721e+00
 * time: 2262.28914809227
   281     1.068384e+03     2.938192e+00
 * time: 2269.742798089981
   282     1.068384e+03     2.942962e+00
 * time: 2277.0469329357147
   283     1.068384e+03     2.943184e+00
 * time: 2284.4481179714203
   284     1.068384e+03     2.943716e+00
 * time: 2291.9473390579224
   285     1.068384e+03     2.944531e+00
 * time: 2299.438082933426
   286     1.068384e+03     2.944646e+00
 * time: 2307.0241260528564
   287     1.068384e+03     2.944770e+00
 * time: 2315.892790079117
   288     1.068384e+03     2.944962e+00
 * time: 2323.6786000728607
   289     1.068384e+03     2.944984e+00
 * time: 2332.1880509853363
   290     1.068384e+03     2.945026e+00
 * time: 2340.5053429603577
   291     1.068384e+03     2.945033e+00
 * time: 2348.7700939178467
   292     1.068384e+03     2.945039e+00
 * time: 2357.4254760742188
   293     1.068384e+03     2.945044e+00
 * time: 2366.2432069778442
   294     1.068384e+03     2.945044e+00
 * time: 2374.7894558906555
   295     1.068384e+03     2.945044e+00
 * time: 2383.451961994171
   296     1.068384e+03     2.945044e+00
 * time: 2391.987457036972
   297     1.068384e+03     2.945044e+00
 * time: 2400.915272951126
   298     1.068384e+03     2.945044e+00
 * time: 2410.190519094467
   299     1.068384e+03     2.945044e+00
 * time: 2419.0747430324554
   300     1.068384e+03     2.945044e+00
 * time: 2428.338721036911
   301     1.068384e+03     2.945044e+00
 * time: 2438.0237119197845
   302     1.068384e+03     2.945044e+00
 * time: 2446.6547570228577
   303     1.068384e+03     2.945044e+00
 * time: 2455.5501260757446
   304     1.068384e+03     2.945044e+00
 * time: 2463.875478029251
   305     1.068384e+03     3.074478e+00
 * time: 2470.6915628910065
   306     1.068384e+03     3.057700e+00
 * time: 2477.4511439800262
   307     1.068384e+03     3.030813e+00
 * time: 2484.2298719882965
   308     1.068384e+03     3.005745e+00
 * time: 2491.0156400203705
   309     1.068384e+03     2.974044e+00
 * time: 2497.9032928943634
   310     1.068384e+03     2.945854e+00
 * time: 2504.6720700263977
   311     1.068383e+03     2.905870e+00
 * time: 2511.4514129161835
   312     1.068382e+03     2.819225e+00
 * time: 2518.258208990097
   313     1.068381e+03     2.581914e+00
 * time: 2525.096179008484
   314     1.068376e+03     1.940126e+00
 * time: 2531.968715906143
   315     1.068367e+03     1.682057e+00
 * time: 2538.83180809021
   316     1.068350e+03     2.787006e+00
 * time: 2545.6913990974426
   317     1.068331e+03     6.870737e+00
 * time: 2552.5707199573517
   318     1.068322e+03     9.136899e+00
 * time: 2559.435222864151
   319     1.068319e+03     9.093888e+00
 * time: 2566.283092021942
   320     1.068318e+03     8.702840e+00
 * time: 2573.127382040024
   321     1.068317e+03     8.067498e+00
 * time: 2579.9573950767517
   322     1.068313e+03     7.024566e+00
 * time: 2586.776678085327
   323     1.068305e+03     5.566463e+00
 * time: 2593.6040070056915
   324     1.068294e+03     4.311204e+00
 * time: 2600.419604063034
   325     1.068285e+03     4.366941e+00
 * time: 2607.4299490451813
   326     1.068282e+03     5.297662e+00
 * time: 2614.3870170116425
   327     1.068282e+03     5.794863e+00
 * time: 2621.324644088745
   328     1.068282e+03     5.858759e+00
 * time: 2628.2105309963226
   329     1.068282e+03     5.858759e+00
 * time: 2635.8782579898834
   330     1.068282e+03     5.890965e+00
 * time: 2642.7700119018555
   331     1.068282e+03     5.889642e+00
 * time: 2649.921215057373
   332     1.068282e+03     5.755927e+00
 * time: 2657.00225687027
   333     1.068282e+03     5.654191e+00
 * time: 2664.053260087967
   334     1.068281e+03     5.457610e+00
 * time: 2671.0283830165863
   335     1.068280e+03     5.325147e+00
 * time: 2678.223057985306
   336     1.068280e+03     5.359845e+00
 * time: 2685.3982009887695
   337     1.068279e+03     5.558458e+00
 * time: 2692.336699962616
   338     1.068278e+03     5.765445e+00
 * time: 2699.8987300395966
   339     1.068278e+03     5.998734e+00
 * time: 2707.4405229091644
   340     1.068276e+03     6.340911e+00
 * time: 2714.4940259456635
   341     1.068272e+03     6.826786e+00
 * time: 2721.5697689056396
   342     1.068262e+03     7.444708e+00
 * time: 2728.8970019817352
   343     1.068237e+03     7.966869e+00
 * time: 2736.2187399864197
   344     1.068187e+03     7.662772e+00
 * time: 2743.5834410190582
   345     1.068105e+03     5.453572e+00
 * time: 2750.612259864807
   346     1.068030e+03     2.116637e+00
 * time: 2757.680116891861
   347     1.068004e+03     2.672269e-01
 * time: 2764.9063789844513
   348     1.068001e+03     4.076140e-01
 * time: 2771.929300069809
   349     1.067999e+03     5.992600e-01
 * time: 2778.8596448898315
   350     1.067997e+03     5.810130e-01
 * time: 2785.7961809635162
   351     1.067994e+03     3.112045e-01
 * time: 2795.1923899650574
   352     1.067992e+03     7.689723e-02
 * time: 2802.5668959617615
   353     1.067992e+03     9.091969e-02
 * time: 2810.21625995636
   354     1.067992e+03     9.785125e-02
 * time: 2817.8544459342957
   355     1.067992e+03     1.024830e-01
 * time: 2825.4843440055847
   356     1.067992e+03     1.051058e-01
 * time: 2833.2433738708496
   357     1.067992e+03     1.057116e-01
 * time: 2840.4835329055786
   358     1.067992e+03     1.057207e-01
 * time: 2848.0463030338287
   359     1.067992e+03     1.057207e-01
 * time: 2856.4472219944
   360     1.067992e+03     1.057044e-01
 * time: 2864.2110888957977
   361     1.067992e+03     1.056554e-01
 * time: 2871.9153439998627
   362     1.067992e+03     1.056554e-01
 * time: 2880.530816078186
   363     1.067992e+03     1.052666e-01
 * time: 2889.360293865204
   364     1.067992e+03     1.052895e-01
 * time: 2898.2155590057373
   365     1.067992e+03     1.052895e-01
 * time: 2907.4585468769073
   366     1.067992e+03     1.052895e-01
 * time: 2916.890515089035
FittedPumasModel

Dynamical system type:               Nonlinear ODE
Solver(s):        OrdinaryDiffEqRosenbrock.Rodas5P

Number of subjects:                             32

Observation records:         Active        Missing
    conc:                       251             47
    pca:                        232             66
    Total:                      483            113

Number of parameters:      Constant      Optimized
                                  0             18

Likelihood approximation:                     FOCE
Likelihood optimizer:                         BFGS

Termination Reason:              NoObjectiveChange
Log-likelihood value:                   -1067.9916

-----------------------
            Estimate
-----------------------
pop_CL       0.13521
pop_V        8.0132
pop_tabs     0.57101
pop_lag      0.87564
pop_e0      96.399
pop_emax    -1.0615
pop_c50      1.4912
pop_tover   14.05
pk_Ω₁,₁      0.068018
pk_Ω₂,₂      0.02105
pk_Ω₃,₃      0.86339
pd_Ω₁,₁      0.0029815
pd_Ω₂,₂      2.3946e-7
pd_Ω₃,₃      0.14556
pd_Ω₄,₄      0.015351
σ_prop       0.088484
σ_add        0.41684
σ_fx         3.5802
-----------------------

On the other hand, if it is known that a differential equation is non-stiff (this might be difficult to guarantee for all admissible parameter values), a non-stiff solver such as Tsit5 at high tolerances or Vern7 at low tolerances could be an alternative to the default solver:

# Fitting with the non-stiff solver Vern7 at low tolerances (relative: 1e-8, absolute: 1e-12)
fit(
    warfarin_pkpd_model,
    pop,
    init_params(warfarin_pkpd_model),
    FOCE();
    diffeq_options = (; alg = Vern7(), reltol = 1e-8, abstol = 1e-12),
)
[ Info: Checking the initial parameter values.
[ Info: The initial negative log likelihood and its gradient are finite. Check passed.
Iter     Function value   Gradient norm 
     0     3.125741e+06     5.911802e+06
 * time: 2.8848648071289062e-5
     1     5.174461e+05     8.708698e+05
 * time: 2.2333338260650635
     2     3.865265e+05     6.344302e+05
 * time: 3.731431007385254
     3     1.804274e+05     2.829723e+05
 * time: 5.179621934890747
     4     9.706640e+04     1.550547e+05
 * time: 6.615917921066284
     5     4.769637e+04     6.778818e+04
 * time: 8.036172866821289
     6     2.902319e+04     3.499747e+04
 * time: 9.408237934112549
     7     1.823472e+04     1.705751e+04
 * time: 10.888195991516113
     8     1.258819e+04     9.569381e+03
 * time: 12.373081922531128
     9     9.389984e+03     8.615851e+03
 * time: 13.837177991867065
    10     7.314702e+03     7.636883e+03
 * time: 15.313628911972046
    11     5.916029e+03     6.624325e+03
 * time: 16.786343812942505
    12     4.930519e+03     5.558140e+03
 * time: 18.250086784362793
    13     4.125060e+03     4.315759e+03
 * time: 19.702292919158936
    14     3.549280e+03     3.051093e+03
 * time: 21.151182889938354
    15     3.283489e+03     2.157292e+03
 * time: 22.602295875549316
    16     3.204886e+03     1.659798e+03
 * time: 24.07211184501648
    17     3.194875e+03     1.480528e+03
 * time: 25.452760934829712
    18     3.193944e+03     1.437921e+03
 * time: 26.891008853912354
    19     3.193070e+03     1.411186e+03
 * time: 28.31724786758423
    20     3.190129e+03     1.355327e+03
 * time: 29.68156599998474
    21     3.183228e+03     1.276603e+03
 * time: 31.041510820388794
    22     3.164897e+03     1.151838e+03
 * time: 32.43494486808777
    23     3.119250e+03     9.712651e+02
 * time: 33.801060914993286
    24     3.006297e+03     7.204342e+02
 * time: 35.13729381561279
    25     2.738913e+03     4.050545e+02
 * time: 36.43084478378296
    26     2.123834e+03     2.318194e+02
 * time: 37.63926887512207
    27     1.789139e+03     2.290465e+02
 * time: 38.911783933639526
Warning: Interrupted. Larger maxiters is needed. If you are using an integrator for non-stiff ODEs or an automatic switching algorithm (the default), you may want to consider using a method for stiff equations. See the solver pages for more details (e.g. https://docs.sciml.ai/DiffEqDocs/stable/solvers/ode_solve/#Stiff-Problems).
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:589
Warning: Interrupted. Larger maxiters is needed. If you are using an integrator for non-stiff ODEs or an automatic switching algorithm (the default), you may want to consider using a method for stiff equations. See the solver pages for more details (e.g. https://docs.sciml.ai/DiffEqDocs/stable/solvers/ode_solve/#Stiff-Problems).
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:589
Warning: Terminated early due to NaN in gradient.
@ Optim ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/Optim/7krni/src/multivariate/optimize/optimize.jl:117
Warning: Interrupted. Larger maxiters is needed. If you are using an integrator for non-stiff ODEs or an automatic switching algorithm (the default), you may want to consider using a method for stiff equations. See the solver pages for more details (e.g. https://docs.sciml.ai/DiffEqDocs/stable/solvers/ode_solve/#Stiff-Problems).
@ SciMLBase ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/SciMLBase/JKXkh/src/integrator_interface.jl:589
    28     1.576318e+03     2.147821e+02
 * time: 48.31771779060364
    29     1.380652e+03     1.621863e+02
 * time: 54.60399580001831
    30     1.298107e+03     1.130479e+02
 * time: 55.961283922195435
    31     1.271740e+03     2.292541e+02
 * time: 57.23762583732605
    32     1.255835e+03     1.721669e+02
 * time: 58.50220584869385
    33     1.251089e+03     1.813354e+02
 * time: 59.77135181427002
    34     1.243725e+03     1.920537e+02
 * time: 61.05448389053345
    35     1.241416e+03     1.835909e+02
 * time: 62.328558921813965
    36     1.240510e+03     1.715569e+02
 * time: 63.60202097892761
    37     1.240496e+03     1.710861e+02
 * time: 64.8607850074768
    38     1.240467e+03     1.703009e+02
 * time: 66.13109183311462
    39     1.240383e+03     1.685321e+02
 * time: 67.3918068408966
    40     1.240176e+03     1.649610e+02
 * time: 68.6569299697876
    41     1.239647e+03     1.571549e+02
 * time: 69.92803978919983
    42     1.238394e+03     1.407042e+02
 * time: 71.19908690452576
    43     1.235743e+03     1.084408e+02
 * time: 72.44106483459473
    44     1.231513e+03     5.668753e+01
 * time: 73.66167998313904
    45     1.227771e+03     4.125472e+01
 * time: 74.88389182090759
    46     1.226339e+03     5.546989e+01
 * time: 76.11234188079834
    47     1.226095e+03     4.927853e+01
 * time: 77.3901309967041
    48     1.226086e+03     4.642266e+01
 * time: 78.65242981910706
    49     1.226086e+03     4.611503e+01
 * time: 79.87912797927856
    50     1.226081e+03     4.478422e+01
 * time: 81.13784980773926
    51     1.226071e+03     4.294093e+01
 * time: 82.41126084327698
    52     1.226042e+03     3.911828e+01
 * time: 83.66753101348877
    53     1.225973e+03     3.210937e+01
 * time: 84.90588688850403
    54     1.225806e+03     2.839654e+01
 * time: 86.15470290184021
    55     1.225466e+03     2.859127e+01
 * time: 87.4140989780426
    56     1.224959e+03     3.226886e+01
 * time: 88.6843159198761
    57     1.224556e+03     4.925686e+01
 * time: 89.9598228931427
    58     1.224428e+03     4.689186e+01
 * time: 91.23084998130798
    59     1.224411e+03     4.101617e+01
 * time: 92.47948694229126
    60     1.224410e+03     3.916788e+01
 * time: 93.74462485313416
    61     1.224408e+03     3.787270e+01
 * time: 94.98624992370605
    62     1.224402e+03     3.519636e+01
 * time: 96.24421691894531
    63     1.224389e+03     3.233949e+01
 * time: 97.49690794944763
    64     1.224351e+03     3.054354e+01
 * time: 98.76662087440491
    65     1.224256e+03     2.816053e+01
 * time: 100.01584196090698
    66     1.224007e+03     2.821380e+01
 * time: 101.27148079872131
    67     1.223382e+03     3.119472e+01
 * time: 102.53297185897827
    68     1.221919e+03     6.976985e+01
 * time: 103.81634092330933
    69     1.219110e+03     1.073633e+02
 * time: 105.01742792129517
    70     1.215576e+03     1.072842e+02
 * time: 106.19050884246826
    71     1.213034e+03     8.400960e+01
 * time: 107.36192297935486
    72     1.212294e+03     8.951044e+01
 * time: 108.56186079978943
    73     1.212259e+03     8.933198e+01
 * time: 109.74496579170227
    74     1.212255e+03     8.895637e+01
 * time: 110.9097728729248
    75     1.212241e+03     8.777217e+01
 * time: 112.10962581634521
    76     1.212214e+03     8.600288e+01
 * time: 113.32086777687073
    77     1.212135e+03     8.213714e+01
 * time: 114.5501389503479
    78     1.211943e+03     7.451404e+01
 * time: 115.76547384262085
    79     1.211464e+03     5.844663e+01
 * time: 116.94675087928772
    80     1.210406e+03     6.363959e+01
 * time: 118.1483428478241
    81     1.208527e+03     7.916604e+01
 * time: 119.35058283805847
    82     1.206464e+03     8.366506e+01
 * time: 120.55367088317871
    83     1.205476e+03     1.005964e+02
 * time: 121.73480582237244
    84     1.205305e+03     8.882827e+01
 * time: 122.92152285575867
    85     1.205293e+03     8.309057e+01
 * time: 124.08534288406372
    86     1.205290e+03     8.172481e+01
 * time: 125.25852084159851
    87     1.205275e+03     7.814716e+01
 * time: 126.47384786605835
    88     1.205243e+03     7.364643e+01
 * time: 127.66153693199158
    89     1.205155e+03     6.632764e+01
 * time: 128.84665989875793
    90     1.204934e+03     6.325952e+01
 * time: 130.03138279914856
    91     1.204369e+03     5.693461e+01
 * time: 131.2556118965149
    92     1.203050e+03     5.234111e+01
 * time: 132.44794082641602
    93     1.200504e+03     5.128249e+01
 * time: 133.64694786071777
    94     1.197282e+03     7.013671e+01
 * time: 134.83573079109192
    95     1.194826e+03     5.064375e+01
 * time: 136.01982378959656
    96     1.193905e+03     4.851059e+01
 * time: 137.2034158706665
    97     1.193833e+03     4.996663e+01
 * time: 138.4188048839569
    98     1.193831e+03     5.008119e+01
 * time: 139.59921789169312
    99     1.193829e+03     5.013190e+01
 * time: 140.7463297843933
   100     1.193824e+03     5.022328e+01
 * time: 141.91279578208923
   101     1.193812e+03     5.034993e+01
 * time: 143.0969319343567
   102     1.193779e+03     5.053003e+01
 * time: 144.26484394073486
   103     1.193695e+03     5.072909e+01
 * time: 145.46637678146362
   104     1.193477e+03     5.080775e+01
 * time: 146.66769790649414
   105     1.192938e+03     5.030899e+01
 * time: 147.87584781646729
   106     1.191706e+03     4.810245e+01
 * time: 149.0541808605194
   107     1.189391e+03     4.971073e+01
 * time: 150.26439690589905
   108     1.186449e+03     8.056474e+01
 * time: 151.4451789855957
   109     1.184524e+03     9.072066e+01
 * time: 152.6276638507843
   110     1.184030e+03     8.460397e+01
 * time: 153.79987692832947
   111     1.183978e+03     7.969454e+01
 * time: 154.9771909713745
   112     1.183972e+03     7.815446e+01
 * time: 156.18289399147034
   113     1.183968e+03     7.789814e+01
 * time: 157.41558194160461
   114     1.183964e+03     7.808136e+01
 * time: 158.8024377822876
   115     1.183956e+03     7.875580e+01
 * time: 160.03819298744202
   116     1.183938e+03     8.003236e+01
 * time: 161.26422500610352
   117     1.183894e+03     8.217667e+01
 * time: 162.4765019416809
   118     1.183783e+03     8.541976e+01
 * time: 163.6682767868042
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   359     1.067991e+03     9.459425e-02
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   360     1.067991e+03     9.459425e-02
 * time: 536.2101719379425
   361     1.067991e+03     9.459425e-02
 * time: 537.8283488750458
   362     1.067991e+03     9.459426e-02
 * time: 539.4456617832184
   363     1.067991e+03     9.459426e-02
 * time: 541.1266949176788
   364     1.067991e+03     9.459426e-02
 * time: 542.7916629314423
   365     1.067991e+03     9.459426e-02
 * time: 544.4413290023804
   366     1.067991e+03     9.459426e-02
 * time: 546.1449677944183
   367     1.067991e+03     9.459426e-02
 * time: 547.6939618587494
   368     1.067991e+03     9.459426e-02
 * time: 549.3151547908783
   369     1.067991e+03     9.459426e-02
 * time: 550.929016828537
   370     1.067991e+03     9.459426e-02
 * time: 552.5268139839172
   371     1.067991e+03     9.459426e-02
 * time: 554.219260931015
   372     1.067991e+03     9.459426e-02
 * time: 554.7838389873505
FittedPumasModel

Dynamical system type:               Nonlinear ODE
Solver(s):              OrdinaryDiffEqVerner.Vern7

Number of subjects:                             32

Observation records:         Active        Missing
    conc:                       251             47
    pca:                        232             66
    Total:                      483            113

Number of parameters:      Constant      Optimized
                                  0             18

Likelihood approximation:                     FOCE
Likelihood optimizer:                         BFGS

Termination Reason:                      NoXChange
Log-likelihood value:                   -1067.9913

-----------------------
            Estimate
-----------------------
pop_CL       0.13521
pop_V        8.0133
pop_tabs     0.57114
pop_lag      0.87561
pop_e0      96.399
pop_emax    -1.0615
pop_c50      1.4912
pop_tover   14.05
pk_Ω₁,₁      0.068012
pk_Ω₂,₂      0.021048
pk_Ω₃,₃      0.86273
pd_Ω₁,₁      0.002977
pd_Ω₂,₂      1.9398e-7
pd_Ω₃,₃      0.14561
pd_Ω₄,₄      0.015351
σ_prop       0.088485
σ_add        0.41684
σ_fx         3.5803
-----------------------

8 Concluding Remarks

In this tutorial, you have seen how to adjust the tolerances and the algorithm of the differential solver. Usually, the default differential equation solver in Pumas is an efficient choice. To reduce numerical issues, sometimes it can be helpful to decrease the default tolerances.