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 ~ @. CombinedNormal(cp, σ_add, σ_prop)
        """
        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     3.130150e+06     5.915753e+06
 * time: 0.04304909706115723
     1     5.185876e+05     8.742030e+05
 * time: 4.374430894851685
     2     3.866954e+05     6.366579e+05
 * time: 5.301578998565674
     3     1.795029e+05     2.835394e+05
 * time: 6.1889190673828125
     4     9.682657e+04     1.546520e+05
 * time: 7.1284019947052
     5     4.791913e+04     6.820049e+04
 * time: 8.015537023544312
     6     2.907378e+04     3.509701e+04
 * time: 8.934067010879517
     7     1.827380e+04     1.713127e+04
 * time: 9.839226961135864
     8     1.260636e+04     9.563331e+03
 * time: 10.720464944839478
     9     9.403443e+03     8.611646e+03
 * time: 11.638986110687256
    10     7.325848e+03     7.634817e+03
 * time: 12.494635105133057
    11     5.926870e+03     6.625147e+03
 * time: 13.357939004898071
    12     4.942281e+03     5.562822e+03
 * time: 14.23684310913086
    13     4.139086e+03     4.326566e+03
 * time: 15.086654901504517
    14     3.563492e+03     3.065260e+03
 * time: 15.918452024459839
    15     3.296158e+03     2.170249e+03
 * time: 16.76041889190674
    16     3.216280e+03     1.669629e+03
 * time: 17.605499982833862
    17     3.205942e+03     1.487868e+03
 * time: 18.42154312133789
    18     3.204980e+03     1.444252e+03
 * time: 19.253813982009888
    19     3.204106e+03     1.417661e+03
 * time: 20.075377941131592
    20     3.201144e+03     1.361617e+03
 * time: 20.88825011253357
    21     3.194217e+03     1.282919e+03
 * time: 21.702234983444214
    22     3.175799e+03     1.158037e+03
 * time: 22.50766897201538
    23     3.130001e+03     9.774739e+02
 * time: 23.33515191078186
    24     3.016853e+03     7.265903e+02
 * time: 24.17748212814331
    25     2.749859e+03     4.107629e+02
 * time: 24.988327980041504
    26     2.137217e+03     2.318395e+02
 * time: 25.770344018936157
    27     1.756675e+03     2.281485e+02
 * time: 26.606022119522095
    28     1.380669e+03     1.613775e+02
 * time: 28.67688798904419
    29     1.328440e+03     1.298802e+02
 * time: 29.417633056640625
    30     1.287369e+03     2.434675e+02
 * time: 30.063885927200317
    31     1.263062e+03     1.616159e+02
 * time: 30.702299118041992
    32     1.254700e+03     1.795912e+02
 * time: 31.325376987457275
    33     1.247195e+03     1.995476e+02
 * time: 31.960274934768677
    34     1.243756e+03     1.937611e+02
 * time: 32.59869599342346
    35     1.240818e+03     1.738948e+02
 * time: 33.2686231136322
    36     1.240776e+03     1.743455e+02
 * time: 33.90410590171814
    37     1.240765e+03     1.742681e+02
 * time: 34.563947916030884
    38     1.240074e+03     1.686540e+02
 * time: 35.19507098197937
    39     1.238981e+03     1.584905e+02
 * time: 35.837584018707275
    40     1.236205e+03     1.301147e+02
 * time: 36.494946002960205
    41     1.232071e+03     8.166215e+01
 * time: 37.151511907577515
    42     1.228115e+03     3.717443e+01
 * time: 37.80254411697388
    43     1.226327e+03     5.239396e+01
 * time: 38.451884031295776
    44     1.226024e+03     4.861318e+01
 * time: 39.10285997390747
    45     1.226011e+03     4.580542e+01
 * time: 39.762574911117554
    46     1.226010e+03     4.534695e+01
 * time: 40.41445302963257
    47     1.226008e+03     4.462779e+01
 * time: 41.08552002906799
    48     1.226002e+03     4.331824e+01
 * time: 41.74311900138855
    49     1.225987e+03     4.094327e+01
 * time: 42.39648103713989
    50     1.225949e+03     3.642019e+01
 * time: 43.080918073654175
    51     1.225855e+03     2.864881e+01
 * time: 43.74250912666321
    52     1.225639e+03     2.863354e+01
 * time: 44.409523010253906
    53     1.225232e+03     3.020554e+01
 * time: 45.06808304786682
    54     1.224729e+03     4.103561e+01
 * time: 45.725642919540405
    55     1.224434e+03     5.071657e+01
 * time: 46.39027690887451
    56     1.224368e+03     4.548491e+01
 * time: 47.02430295944214
    57     1.224361e+03     4.120954e+01
 * time: 47.674741983413696
    58     1.224360e+03     4.006985e+01
 * time: 48.327943086624146
    59     1.224357e+03     3.801109e+01
 * time: 48.98255896568298
    60     1.224349e+03     3.498015e+01
 * time: 49.65358805656433
    61     1.224327e+03     3.147637e+01
 * time: 50.28519797325134
    62     1.224271e+03     2.931465e+01
 * time: 50.93686890602112
    63     1.224126e+03     2.814671e+01
 * time: 51.59349489212036
    64     1.223753e+03     2.816101e+01
 * time: 52.25110197067261
    65     1.222837e+03     4.614252e+01
 * time: 52.9343740940094
    66     1.220832e+03     8.757572e+01
 * time: 53.58036398887634
    67     1.217567e+03     1.138929e+02
 * time: 54.23774695396423
    68     1.214404e+03     8.919354e+01
 * time: 54.885634899139404
    69     1.212787e+03     8.410207e+01
 * time: 55.51684808731079
    70     1.212569e+03     8.598204e+01
 * time: 56.137048959732056
    71     1.212562e+03     8.564567e+01
 * time: 56.74971008300781
    72     1.212557e+03     8.527574e+01
 * time: 57.37280893325806
    73     1.212540e+03     8.422259e+01
 * time: 57.99724006652832
    74     1.212503e+03     8.240816e+01
 * time: 58.61121392250061
    75     1.212401e+03     7.843332e+01
 * time: 59.24232292175293
    76     1.212148e+03     7.012172e+01
 * time: 59.90290689468384
    77     1.211531e+03     5.213081e+01
 * time: 60.53248310089111
    78     1.210204e+03     7.305043e+01
 * time: 61.187443017959595
    79     1.208013e+03     8.679967e+01
 * time: 61.79960608482361
    80     1.205949e+03     9.839154e+01
 * time: 62.422693967819214
    81     1.205142e+03     1.083109e+02
 * time: 63.04945492744446
    82     1.205024e+03     9.689232e+01
 * time: 63.674262046813965
    83     1.205016e+03     9.287604e+01
 * time: 64.29216194152832
    84     1.205012e+03     9.131434e+01
 * time: 64.91503095626831
    85     1.204994e+03     8.785522e+01
 * time: 65.51611804962158
    86     1.204955e+03     8.321345e+01
 * time: 66.1206750869751
    87     1.204846e+03     7.512847e+01
 * time: 66.69163703918457
    88     1.204571e+03     6.677960e+01
 * time: 67.31184101104736
    89     1.203874e+03     5.917097e+01
 * time: 67.93780899047852
    90     1.202256e+03     5.625398e+01
 * time: 68.55029201507568
    91     1.199255e+03     5.407775e+01
 * time: 69.15749001502991
    92     1.195772e+03     6.418968e+01
 * time: 69.77275490760803
    93     1.193272e+03     4.385779e+01
 * time: 70.37839889526367
    94     1.192403e+03     4.695234e+01
 * time: 70.9763240814209
    95     1.192345e+03     4.824611e+01
 * time: 71.54971098899841
    96     1.192343e+03     4.834837e+01
 * time: 72.15219306945801
    97     1.192341e+03     4.841664e+01
 * time: 72.7602128982544
    98     1.192337e+03     4.853485e+01
 * time: 73.34136509895325
    99     1.192326e+03     4.872157e+01
 * time: 73.9321780204773
   100     1.192298e+03     4.900641e+01
 * time: 74.54442811012268
   101     1.192226e+03     4.940187e+01
 * time: 75.15099310874939
   102     1.192043e+03     4.983597e+01
 * time: 75.75468301773071
   103     1.191590e+03     4.998730e+01
 * time: 76.33803391456604
   104     1.190555e+03     4.888824e+01
 * time: 76.9432909488678
   105     1.188610e+03     4.476259e+01
 * time: 77.5702760219574
   106     1.186163e+03     5.610726e+01
 * time: 78.21266603469849
   107     1.184413e+03     7.224666e+01
 * time: 78.88323402404785
   108     1.183656e+03     7.490583e+01
 * time: 79.53874802589417
   109     1.183479e+03     7.310985e+01
 * time: 80.18608212471008
   110     1.183445e+03     7.276225e+01
 * time: 80.85224199295044
   111     1.183435e+03     7.362156e+01
 * time: 81.49638104438782
   112     1.183432e+03     7.447416e+01
 * time: 82.15064811706543
   113     1.183428e+03     7.576303e+01
 * time: 82.80592393875122
   114     1.183422e+03     7.712921e+01
 * time: 83.4615490436554
   115     1.183402e+03     7.954539e+01
 * time: 84.10541200637817
   116     1.183354e+03     8.304573e+01
 * time: 84.72451710700989
   117     1.183227e+03     8.811035e+01
 * time: 85.35203289985657
   118     1.182910e+03     9.433287e+01
 * time: 85.9739100933075
   119     1.182159e+03     9.929986e+01
 * time: 86.66459608078003
   120     1.180613e+03     9.583938e+01
 * time: 87.37240099906921
   121     1.178253e+03     7.334167e+01
 * time: 88.12905406951904
   122     1.176240e+03     3.397205e+01
 * time: 88.89573311805725
   123     1.175532e+03     1.920932e+01
 * time: 89.6529049873352
   124     1.175411e+03     1.932720e+01
 * time: 90.40943789482117
   125     1.175397e+03     1.965053e+01
 * time: 91.13668489456177
   126     1.175396e+03     1.966443e+01
 * time: 91.86466789245605
   127     1.175395e+03     1.960396e+01
 * time: 92.58368992805481
   128     1.175395e+03     1.957495e+01
 * time: 93.3163890838623
   129     1.175393e+03     1.946094e+01
 * time: 94.0526270866394
   130     1.175388e+03     1.938728e+01
 * time: 94.80828309059143
   131     1.175375e+03     1.916215e+01
 * time: 95.54454493522644
   132     1.175343e+03     1.894152e+01
 * time: 96.29219794273376
   133     1.175257e+03     1.842699e+01
 * time: 97.03752589225769
   134     1.175031e+03     1.935678e+01
 * time: 97.81835508346558
   135     1.174436e+03     2.681160e+01
 * time: 98.62505197525024
   136     1.172888e+03     3.945075e+01
 * time: 99.43357110023499
   137     1.169017e+03     5.876234e+01
 * time: 100.22343802452087
   138     1.160885e+03     7.779933e+01
 * time: 101.01137089729309
   139     1.152001e+03     6.044664e+01
 * time: 101.81194806098938
   140     1.150076e+03     2.093881e+02
 * time: 102.63891005516052
   141     1.147572e+03     1.330305e+02
 * time: 103.44896912574768
   142     1.143865e+03     2.372423e+01
 * time: 104.25883507728577
   143     1.142815e+03     2.227954e+01
 * time: 105.01806092262268
   144     1.141776e+03     3.847481e+01
 * time: 105.71958708763123
   145     1.141295e+03     2.197611e+01
 * time: 106.40395903587341
   146     1.140996e+03     2.098791e+01
 * time: 107.1034779548645
   147     1.140982e+03     2.095235e+01
 * time: 107.79986906051636
   148     1.140979e+03     2.098518e+01
 * time: 108.48278093338013
   149     1.140978e+03     2.101190e+01
 * time: 109.18417692184448
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:                   -1140.9777

-----------------------
            Estimate
-----------------------
pop_CL       0.13722
pop_V        7.8506
pop_tabs     1.084
pop_lag      0.35905
pop_e0      96.351
pop_emax    -1.0615
pop_c50      1.4777
pop_tover   14.461
pk_Ω₁,₁      0.25384
pk_Ω₂,₂      0.042739
pk_Ω₃,₃      0.22544
pd_Ω₁,₁      0.0027398
pd_Ω₂,₂      0.0021862
pd_Ω₃,₃      0.01899
pd_Ω₄,₄      0.017768
σ_prop       0.013046
σ_add        0.9655
σ_fx         3.4529
-----------------------

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: 2.4080276489257812e-5
     1     5.174461e+05     8.708698e+05
 * time: 1.9264459609985352
     2     3.865265e+05     6.344302e+05
 * time: 3.6215500831604004
     3     1.804274e+05     2.829723e+05
 * time: 5.311941146850586
     4     9.706640e+04     1.550547e+05
 * time: 7.100191116333008
     5     4.769637e+04     6.778818e+04
 * time: 9.231323003768921
     6     2.902319e+04     3.499747e+04
 * time: 11.345361948013306
     7     1.823472e+04     1.705751e+04
 * time: 13.300086975097656
     8     1.258819e+04     9.569381e+03
 * time: 15.35813307762146
     9     9.389984e+03     8.615851e+03
 * time: 17.143139123916626
    10     7.314702e+03     7.636883e+03
 * time: 19.658288955688477
    11     5.916029e+03     6.624325e+03
 * time: 21.538336992263794
    12     4.930519e+03     5.558140e+03
 * time: 23.261306047439575
    13     4.125060e+03     4.315759e+03
 * time: 24.986050128936768
    14     3.549280e+03     3.051093e+03
 * time: 26.742098093032837
    15     3.283489e+03     2.157292e+03
 * time: 28.55439805984497
    16     3.204886e+03     1.659798e+03
 * time: 30.403362035751343
    17     3.194875e+03     1.480528e+03
 * time: 32.1552300453186
    18     3.193944e+03     1.437921e+03
 * time: 33.897090911865234
    19     3.193070e+03     1.411186e+03
 * time: 35.60795497894287
    20     3.190129e+03     1.355327e+03
 * time: 37.324695110321045
    21     3.183228e+03     1.276603e+03
 * time: 39.01523494720459
    22     3.164897e+03     1.151838e+03
 * time: 40.80250692367554
    23     3.119250e+03     9.712651e+02
 * time: 42.45875406265259
    24     3.006297e+03     7.204342e+02
 * time: 44.06330108642578
    25     2.738913e+03     4.050545e+02
 * time: 45.6571409702301
    26     2.123834e+03     2.318194e+02
 * time: 47.12534809112549
    27     1.789138e+03     2.290465e+02
 * time: 48.67637300491333
    28     1.396455e+03     1.683969e+02
 * time: 53.67441201210022
    29     1.333545e+03     1.336195e+02
 * time: 55.302868127822876
    30     1.297771e+03     2.452189e+02
 * time: 56.621626138687134
    31     1.266002e+03     1.523968e+02
 * time: 57.921355962753296
    32     1.255506e+03     1.733993e+02
 * time: 59.224332094192505
    33     1.247789e+03     1.971624e+02
 * time: 60.60240292549133
    34     1.244490e+03     1.915728e+02
 * time: 61.8923180103302
    35     1.240568e+03     1.704250e+02
 * time: 63.19865608215332
    36     1.240503e+03     1.711787e+02
 * time: 64.56064796447754
    37     1.240492e+03     1.711657e+02
 * time: 65.89852809906006
    38     1.239992e+03     1.687239e+02
 * time: 67.2195451259613
    39     1.239199e+03     1.624610e+02
 * time: 68.56213092803955
    40     1.236971e+03     1.400045e+02
 * time: 69.96357011795044
    41     1.233203e+03     9.442284e+01
 * time: 71.41717910766602
    42     1.228682e+03     3.273925e+01
 * time: 72.74443507194519
    43     1.226466e+03     4.997777e+01
 * time: 74.0948920249939
    44     1.226104e+03     4.904407e+01
 * time: 75.45070314407349
    45     1.226088e+03     4.675833e+01
 * time: 76.85252714157104
    46     1.226088e+03     4.628496e+01
 * time: 78.81465411186218
    47     1.226085e+03     4.541356e+01
 * time: 80.2940320968628
    48     1.226080e+03     4.402741e+01
 * time: 81.62674403190613
    49     1.226064e+03     4.142300e+01
 * time: 82.98249101638794
    50     1.226026e+03     3.663066e+01
 * time: 84.3319480419159
    51     1.225931e+03     2.851375e+01
 * time: 85.72894096374512
    52     1.225713e+03     2.844436e+01
 * time: 87.12494897842407
    53     1.225303e+03     3.026439e+01
 * time: 88.61104798316956
    54     1.224791e+03     4.157122e+01
 * time: 90.0492091178894
    55     1.224489e+03     5.047474e+01
 * time: 91.42541694641113
    56     1.224420e+03     4.451066e+01
 * time: 92.79210114479065
    57     1.224413e+03     3.994027e+01
 * time: 94.08522295951843
    58     1.224412e+03     3.879446e+01
 * time: 95.3483989238739
    59     1.224408e+03     3.677251e+01
 * time: 96.67338299751282
    60     1.224400e+03     3.377994e+01
 * time: 97.9625039100647
    61     1.224379e+03     3.158188e+01
 * time: 99.26274108886719
    62     1.224324e+03     2.925156e+01
 * time: 100.58178091049194
    63     1.224180e+03     2.815886e+01
 * time: 101.93912601470947
    64     1.223813e+03     2.818297e+01
 * time: 103.3219940662384
    65     1.222906e+03     4.598741e+01
 * time: 104.76218891143799
    66     1.220910e+03     8.692124e+01
 * time: 106.10996508598328
    67     1.217609e+03     1.136529e+02
 * time: 107.39196300506592
    68     1.214313e+03     9.030293e+01
 * time: 108.67836713790894
    69     1.212533e+03     8.868945e+01
 * time: 109.96242499351501
    70     1.212272e+03     8.970280e+01
 * time: 111.2830970287323
    71     1.212264e+03     8.921923e+01
 * time: 112.58584213256836
    72     1.212259e+03     8.882367e+01
 * time: 113.84140491485596
    73     1.212242e+03     8.761510e+01
 * time: 115.08940410614014
    74     1.212205e+03     8.561996e+01
 * time: 116.39553594589233
    75     1.212103e+03     8.125316e+01
 * time: 117.7300591468811
    76     1.211850e+03     7.229635e+01
 * time: 119.1615560054779
    77     1.211238e+03     5.321840e+01
 * time: 120.50576114654541
    78     1.209945e+03     7.377542e+01
 * time: 121.8812530040741
    79     1.207890e+03     8.404090e+01
 * time: 123.41842699050903
    80     1.206058e+03     9.148111e+01
 * time: 124.96521091461182
    81     1.205389e+03     9.689402e+01
 * time: 126.65228700637817
    82     1.205303e+03     8.594691e+01
 * time: 128.26258897781372
    83     1.205297e+03     8.262969e+01
 * time: 129.8500349521637
    84     1.205293e+03     8.096366e+01
 * time: 131.38830304145813
    85     1.205277e+03     7.747617e+01
 * time: 132.97641110420227
    86     1.205241e+03     7.259257e+01
 * time: 134.58031010627747
    87     1.205143e+03     6.664833e+01
 * time: 136.17957496643066
    88     1.204895e+03     6.374646e+01
 * time: 137.80389499664307
    89     1.204268e+03     5.753767e+01
 * time: 139.44229412078857
    90     1.202818e+03     4.866324e+01
 * time: 141.06299901008606
    91     1.200116e+03     5.085841e+01
 * time: 142.6771800518036
    92     1.196895e+03     7.139478e+01
 * time: 144.25075101852417
    93     1.194610e+03     4.693643e+01
 * time: 145.7862319946289
    94     1.193880e+03     4.874637e+01
 * time: 147.5923149585724
    95     1.193833e+03     4.997341e+01
 * time: 149.19410705566406
    96     1.193831e+03     5.008752e+01
 * time: 150.72522807121277
    97     1.193829e+03     5.014860e+01
 * time: 152.2506000995636
    98     1.193824e+03     5.025195e+01
 * time: 153.80788111686707
    99     1.193812e+03     5.040245e+01
 * time: 155.39248609542847
   100     1.193778e+03     5.061928e+01
 * time: 156.99573802947998
   101     1.193693e+03     5.087910e+01
 * time: 158.5734519958496
   102     1.193472e+03     5.105104e+01
 * time: 160.24349403381348
   103     1.192926e+03     5.068579e+01
 * time: 161.8205690383911
   104     1.191681e+03     4.863476e+01
 * time: 163.42136001586914
   105     1.189351e+03     4.892981e+01
 * time: 164.99288511276245
   106     1.186420e+03     7.777396e+01
 * time: 166.55275011062622
   107     1.184527e+03     8.874389e+01
 * time: 168.7089409828186
   108     1.184034e+03     8.377338e+01
 * time: 171.10128712654114
   109     1.183978e+03     7.932701e+01
 * time: 173.41671514511108
   110     1.183969e+03     7.794331e+01
 * time: 175.1115961074829
   111     1.183966e+03     7.787273e+01
 * time: 176.77953791618347
   112     1.183962e+03     7.833691e+01
 * time: 178.40836191177368
   113     1.183955e+03     7.929110e+01
 * time: 180.0189290046692
   114     1.183940e+03     8.084135e+01
 * time: 181.63363313674927
   115     1.183904e+03     8.331063e+01
 * time: 183.09229397773743
   116     1.183812e+03     8.698431e+01
 * time: 184.42673993110657
   117     1.183576e+03     9.188955e+01
 * time: 185.76647400856018
   118     1.182997e+03     9.668923e+01
 * time: 187.13028192520142
   119     1.181702e+03     9.635663e+01
 * time: 188.48431611061096
   120     1.179436e+03     8.061104e+01
 * time: 189.9547119140625
   121     1.177026e+03     4.571924e+01
 * time: 191.4070589542389
   122     1.175794e+03     1.863482e+01
 * time: 192.93562698364258
   123     1.175474e+03     1.968114e+01
 * time: 194.36725401878357
   124     1.175429e+03     1.958620e+01
 * time: 196.3952910900116
   125     1.175427e+03     1.993702e+01
 * time: 198.36035299301147
   126     1.175426e+03     1.962020e+01
 * time: 199.742938041687
   127     1.175426e+03     1.965822e+01
 * time: 201.1286120414734
   128     1.175424e+03     1.984458e+01
 * time: 202.54816007614136
   129     1.175421e+03     2.001151e+01
 * time: 203.99930906295776
   130     1.175413e+03     2.035203e+01
 * time: 205.8703761100769
   131     1.175392e+03     2.084295e+01
 * time: 207.44330096244812
   132     1.175336e+03     2.164587e+01
 * time: 208.8615279197693
   133     1.175189e+03     2.287862e+01
 * time: 210.2958950996399
   134     1.174801e+03     2.475389e+01
 * time: 212.20414113998413
   135     1.173792e+03     4.143547e+01
 * time: 213.77457809448242
   136     1.171220e+03     7.151620e+01
 * time: 215.25193905830383
   137     1.165144e+03     1.078851e+02
 * time: 216.8346071243286
   138     1.155079e+03     7.750665e+01
 * time: 218.62594199180603
   139     1.149212e+03     6.869318e+01
 * time: 220.43073201179504
   140     1.146920e+03     6.356812e+01
 * time: 222.22938704490662
   141     1.144663e+03     4.948649e+01
 * time: 223.9917130470276
   142     1.143084e+03     2.539146e+01
 * time: 225.68569493293762
   143     1.141829e+03     1.979203e+01
 * time: 227.2562539577484
   144     1.141293e+03     2.050876e+01
 * time: 228.84202194213867
   145     1.141052e+03     2.076835e+01
 * time: 230.4226269721985
   146     1.140979e+03     2.090550e+01
 * time: 232.0257649421692
   147     1.140976e+03     2.094541e+01
 * time: 233.60585713386536
   148     1.140975e+03     2.099653e+01
 * time: 235.2033519744873
   149     1.140974e+03     2.099916e+01
 * time: 236.76998591423035
   150     1.140974e+03     2.099880e+01
 * time: 238.34289002418518
   151     1.140973e+03     2.099210e+01
 * time: 239.91053414344788
   152     1.140972e+03     2.098164e+01
 * time: 241.45025396347046
   153     1.140970e+03     2.096558e+01
 * time: 242.97262811660767
   154     1.140963e+03     2.094349e+01
 * time: 244.46070504188538
   155     1.140947e+03     2.091737e+01
 * time: 245.96425604820251
   156     1.140905e+03     2.089971e+01
 * time: 247.4542441368103
   157     1.140795e+03     2.093518e+01
 * time: 248.96028208732605
   158     1.140505e+03     2.116011e+01
 * time: 250.50602197647095
   159     1.139717e+03     2.228810e+01
 * time: 252.04725098609924
   160     1.137490e+03     3.498511e+01
 * time: 253.63925194740295
   161     1.132263e+03     6.110918e+01
 * time: 255.38517093658447
   162     1.129968e+03     7.039541e+01
 * time: 257.5042860507965
   163     1.128182e+03     7.683714e+01
 * time: 259.8350899219513
   164     1.125103e+03     1.650862e+02
 * time: 261.9781401157379
   165     1.124280e+03     1.517864e+02
 * time: 263.8581840991974
   166     1.117040e+03     4.357927e+01
 * time: 265.67219591140747
   167     1.113054e+03     1.682326e+01
 * time: 267.5351219177246
   168     1.111580e+03     1.039864e+01
 * time: 269.4113600254059
   169     1.111231e+03     1.251104e+01
 * time: 271.3336760997772
   170     1.111199e+03     1.211508e+01
 * time: 273.263267993927
   171     1.111188e+03     1.016533e+01
 * time: 275.20553708076477
   172     1.111187e+03     1.118433e+01
 * time: 277.2009451389313
   173     1.111187e+03     1.065844e+01
 * time: 279.2921419143677
   174     1.111187e+03     1.056109e+01
 * time: 281.3512649536133
   175     1.111187e+03     1.040007e+01
 * time: 283.423926115036
   176     1.111186e+03     1.021364e+01
 * time: 285.5232050418854
   177     1.111185e+03     1.018378e+01
 * time: 287.55338191986084
   178     1.111181e+03     1.018369e+01
 * time: 289.6361141204834
   179     1.111171e+03     1.017993e+01
 * time: 291.73437905311584
   180     1.111145e+03     1.192316e+01
 * time: 293.78419494628906
   181     1.111078e+03     1.924480e+01
 * time: 295.8426089286804
   182     1.110902e+03     3.087569e+01
 * time: 297.9289360046387
   183     1.110452e+03     4.875745e+01
 * time: 300.0049250125885
   184     1.109340e+03     7.388902e+01
 * time: 302.0704700946808
   185     1.106855e+03     1.011723e+02
 * time: 304.16208505630493
   186     1.102508e+03     1.093205e+02
 * time: 306.3426630496979
   187     1.097636e+03     7.378681e+01
 * time: 308.5784990787506
   188     1.094076e+03     3.513410e+01
 * time: 311.02306294441223
   189     1.092642e+03     1.308537e+01
 * time: 313.84518814086914
   190     1.092167e+03     1.503410e+01
 * time: 316.42710995674133
   191     1.091981e+03     4.954189e+00
 * time: 318.997985124588
   192     1.091945e+03     4.327859e+00
 * time: 321.48751401901245
   193     1.091930e+03     4.367441e+00
 * time: 324.00355100631714
   194     1.091905e+03     4.390566e+00
 * time: 326.4400191307068
   195     1.091904e+03     4.349102e+00
 * time: 328.9320149421692
   196     1.091904e+03     4.341803e+00
 * time: 331.4420120716095
   197     1.091904e+03     4.340976e+00
 * time: 333.92163014411926
   198     1.091904e+03     4.340363e+00
 * time: 336.4100251197815
   199     1.091904e+03     4.340202e+00
 * time: 338.9109070301056
   200     1.091904e+03     4.339667e+00
 * time: 341.349769115448
   201     1.091903e+03     4.339103e+00
 * time: 343.78407406806946
   202     1.091902e+03     4.337633e+00
 * time: 346.2082431316376
   203     1.091897e+03     4.396965e+00
 * time: 348.59027099609375
   204     1.091887e+03     7.175436e+00
 * time: 350.9541189670563
   205     1.091858e+03     1.163793e+01
 * time: 353.35459303855896
   206     1.091785e+03     1.870264e+01
 * time: 355.7485101222992
   207     1.091597e+03     2.942648e+01
 * time: 358.2545609474182
   208     1.091143e+03     4.395404e+01
 * time: 360.7460460662842
   209     1.090182e+03     5.754183e+01
 * time: 363.210333108902
   210     1.088777e+03     5.519101e+01
 * time: 365.5472559928894
   211     1.087759e+03     3.383311e+01
 * time: 367.95636200904846
   212     1.087247e+03     2.054519e+01
 * time: 370.16893696784973
   213     1.087056e+03     5.547897e+00
 * time: 372.39060711860657
   214     1.087044e+03     5.434553e+00
 * time: 374.6054310798645
   215     1.087043e+03     5.392743e+00
 * time: 376.79470014572144
   216     1.087043e+03     5.384001e+00
 * time: 379.0371530056
   217     1.087043e+03     5.383274e+00
 * time: 381.22525095939636
   218     1.087043e+03     5.383604e+00
 * time: 383.40769505500793
   219     1.087043e+03     5.385463e+00
 * time: 385.62034702301025
   220     1.087043e+03     5.388083e+00
 * time: 387.8145000934601
   221     1.087042e+03     5.393891e+00
 * time: 390.05332493782043
   222     1.087040e+03     5.405285e+00
 * time: 392.35812497138977
   223     1.087036e+03     5.430225e+00
 * time: 394.64833307266235
   224     1.087024e+03     5.486847e+00
 * time: 396.93525099754333
   225     1.086993e+03     5.623702e+00
 * time: 399.183531999588
   226     1.086908e+03     5.976337e+00
 * time: 401.34924697875977
   227     1.086659e+03     9.111693e+00
 * time: 403.49654507637024
   228     1.086312e+03     2.628154e+01
 * time: 405.50130009651184
   229     1.086061e+03     2.869336e+01
 * time: 407.65267300605774
   230     1.085221e+03     3.372822e+01
 * time: 409.8090989589691
   231     1.083535e+03     3.087903e+01
 * time: 411.6519169807434
   232     1.077842e+03     2.857755e+01
 * time: 413.5770571231842
   233     1.070653e+03     3.102077e+01
 * time: 415.6763780117035
   234     1.069783e+03     1.095905e+01
 * time: 417.6875629425049
   235     1.069619e+03     4.269384e+00
 * time: 419.7079839706421
   236     1.069540e+03     6.758648e+00
 * time: 421.750314950943
   237     1.069493e+03     2.796943e+00
 * time: 423.74147510528564
   238     1.069488e+03     2.235527e+00
 * time: 425.7592921257019
   239     1.069488e+03     2.235622e+00
 * time: 427.746258020401
   240     1.069488e+03     2.235644e+00
 * time: 429.7058939933777
   241     1.069488e+03     2.235528e+00
 * time: 432.31872391700745
   242     1.069488e+03     2.235417e+00
 * time: 435.4149420261383
   243     1.069488e+03     2.235145e+00
 * time: 437.96152901649475
   244     1.069488e+03     2.234685e+00
 * time: 440.1759829521179
   245     1.069488e+03     2.233746e+00
 * time: 442.2327721118927
   246     1.069487e+03     2.231801e+00
 * time: 444.2956030368805
   247     1.069487e+03     2.227499e+00
 * time: 446.4207000732422
   248     1.069485e+03     2.217571e+00
 * time: 448.57989597320557
   249     1.069480e+03     2.283352e+00
 * time: 450.92781805992126
   250     1.069468e+03     3.669300e+00
 * time: 453.54479002952576
   251     1.069439e+03     5.687883e+00
 * time: 455.7288420200348
   252     1.069373e+03     8.225802e+00
 * time: 457.91228699684143
   253     1.069248e+03     1.032624e+01
 * time: 460.1402509212494
   254     1.069088e+03     9.842611e+00
 * time: 462.3554949760437
   255     1.068967e+03     5.346327e+00
 * time: 464.59913206100464
   256     1.068932e+03     8.624372e-01
 * time: 466.842246055603
   257     1.068929e+03     8.679663e-01
 * time: 469.0701720714569
   258     1.068929e+03     8.689411e-01
 * time: 471.2761199474335
   259     1.068929e+03     8.689410e-01
 * time: 473.5900731086731
   260     1.068929e+03     8.689396e-01
 * time: 475.7815170288086
   261     1.068929e+03     8.689396e-01
 * time: 478.5966229438782
   262     1.068929e+03     8.689396e-01
 * time: 481.21020913124084
   263     1.068929e+03     8.689452e-01
 * time: 483.59191703796387
   264     1.068929e+03     8.689537e-01
 * time: 485.8815219402313
   265     1.068929e+03     8.689759e-01
 * time: 488.10483407974243
   266     1.068929e+03     8.689733e-01
 * time: 490.3046851158142
   267     1.068929e+03     8.689308e-01
 * time: 492.4863049983978
   268     1.068929e+03     8.687927e-01
 * time: 494.65591192245483
   269     1.068929e+03     1.146689e+00
 * time: 496.8524000644684
   270     1.068928e+03     1.858717e+00
 * time: 499.05850291252136
   271     1.068926e+03     3.014163e+00
 * time: 501.29847598075867
   272     1.068921e+03     4.850801e+00
 * time: 503.5252649784088
   273     1.068908e+03     7.706317e+00
 * time: 505.74298906326294
   274     1.068876e+03     1.183609e+01
 * time: 507.93011498451233
   275     1.068805e+03     1.674967e+01
 * time: 510.1117241382599
   276     1.068668e+03     1.965804e+01
 * time: 512.2641880512238
   277     1.068489e+03     1.560006e+01
 * time: 514.4509711265564
   278     1.068389e+03     6.429456e+00
 * time: 516.6820991039276
   279     1.068376e+03     1.621982e+00
 * time: 518.8158891201019
   280     1.068375e+03     1.316816e+00
 * time: 520.8768141269684
   281     1.068374e+03     1.288387e+00
 * time: 522.9203379154205
   282     1.068374e+03     1.283839e+00
 * time: 524.9372251033783
   283     1.068374e+03     1.283420e+00
 * time: 526.9508810043335
   284     1.068374e+03     1.283364e+00
 * time: 529.0532050132751
   285     1.068374e+03     1.283194e+00
 * time: 531.1624979972839
   286     1.068374e+03     1.283150e+00
 * time: 533.3684830665588
   287     1.068374e+03     1.283140e+00
 * time: 535.6572020053864
   288     1.068374e+03     1.283106e+00
 * time: 537.9587740898132
   289     1.068374e+03     1.283106e+00
 * time: 540.3918211460114
   290     1.068374e+03     1.276656e+00
 * time: 542.414500951767
   291     1.068374e+03     1.275802e+00
 * time: 544.4127259254456
   292     1.068374e+03     1.269646e+00
 * time: 546.4578399658203
   293     1.068374e+03     1.262258e+00
 * time: 548.5439031124115
   294     1.068373e+03     1.654698e+00
 * time: 550.5818660259247
   295     1.068372e+03     2.668088e+00
 * time: 552.6226511001587
   296     1.068367e+03     4.301261e+00
 * time: 554.6162400245667
   297     1.068356e+03     6.774893e+00
 * time: 556.5164999961853
   298     1.068329e+03     1.013771e+01
 * time: 558.4065270423889
   299     1.068274e+03     1.330560e+01
 * time: 560.4112160205841
   300     1.068187e+03     1.312531e+01
 * time: 562.3544049263
   301     1.068095e+03     7.878246e+00
 * time: 564.3307330608368
   302     1.068036e+03     2.139748e+00
 * time: 566.3571960926056
   303     1.068013e+03     8.037342e-01
 * time: 568.4251699447632
   304     1.068005e+03     1.492898e+00
 * time: 570.4507060050964
   305     1.067999e+03     1.212543e+00
 * time: 572.4567770957947
   306     1.067994e+03     4.245521e-01
 * time: 574.4850800037384
   307     1.067992e+03     8.588518e-02
 * time: 576.4877121448517
   308     1.067992e+03     2.309018e-01
 * time: 578.4897630214691
   309     1.067991e+03     1.646081e-01
 * time: 580.5213279724121
   310     1.067991e+03     9.057167e-02
 * time: 582.5455620288849
   311     1.067991e+03     9.435652e-02
 * time: 584.5624461174011
   312     1.067991e+03     9.436421e-02
 * time: 586.6975400447845
   313     1.067991e+03     9.523930e-02
 * time: 588.7049510478973
   314     1.067991e+03     9.525578e-02
 * time: 590.7153749465942
   315     1.067991e+03     9.529733e-02
 * time: 592.7162311077118
   316     1.067991e+03     9.531681e-02
 * time: 594.7506020069122
   317     1.067991e+03     9.536338e-02
 * time: 597.0153050422668
   318     1.067991e+03     9.542813e-02
 * time: 599.0687401294708
   319     1.067991e+03     9.552402e-02
 * time: 601.1418271064758
   320     1.067991e+03     9.553892e-02
 * time: 603.2980189323425
   321     1.067991e+03     9.553930e-02
 * time: 605.6175971031189
   322     1.067991e+03     9.553937e-02
 * time: 608.0138339996338
   323     1.067991e+03     9.553945e-02
 * time: 610.4070479869843
   324     1.067991e+03     9.553947e-02
 * time: 612.8970830440521
   325     1.067991e+03     9.553951e-02
 * time: 615.3992419242859
   326     1.067991e+03     9.553952e-02
 * time: 617.9610919952393
   327     1.067991e+03     1.960276e-01
 * time: 620.0245850086212
   328     1.067991e+03     2.189747e-01
 * time: 622.0962700843811
   329     1.067991e+03     3.471907e-01
 * time: 624.1733100414276
   330     1.067991e+03     4.746893e-01
 * time: 626.2408180236816
   331     1.067991e+03     6.344881e-01
 * time: 628.3335649967194
   332     1.067991e+03     6.826402e-01
 * time: 630.4052510261536
   333     1.067990e+03     4.682357e-01
 * time: 632.4804561138153
   334     1.067990e+03     1.398439e-01
 * time: 634.5638570785522
   335     1.067990e+03     4.650616e-03
 * time: 636.651242017746
   336     1.067990e+03     4.379178e-03
 * time: 638.8894591331482
   337     1.067990e+03     3.052741e-02
 * time: 640.9970660209656
   338     1.067990e+03     3.052782e-02
 * time: 643.3413770198822
   339     1.067990e+03     3.065948e-02
 * time: 645.4126040935516
   340     1.067990e+03     1.888820e-02
 * time: 647.4826550483704
   341     1.067990e+03     3.159606e-03
 * time: 649.5582120418549
   342     1.067990e+03     2.528974e-03
 * time: 651.7320921421051
   343     1.067990e+03     1.906291e-03
 * time: 653.8983700275421
   344     1.067990e+03     1.487671e-03
 * time: 656.0540759563446
   345     1.067990e+03     1.485038e-03
 * time: 658.3911209106445
   346     1.067990e+03     1.482585e-03
 * time: 660.7250039577484
   347     1.067990e+03     1.480617e-03
 * time: 663.0933740139008
   348     1.067990e+03     1.478874e-03
 * time: 665.43741106987
   349     1.067990e+03     1.477253e-03
 * time: 667.7777979373932
   350     1.067990e+03     1.477237e-03
 * time: 670.2769501209259
   351     1.067990e+03     1.477237e-03
 * time: 673.5101010799408
   352     1.067990e+03     1.477237e-03
 * time: 676.4454209804535
   353     1.067990e+03     1.477237e-03
 * time: 679.8893280029297
   354     1.067990e+03     1.477237e-03
 * time: 683.0715811252594
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:              NoObjectiveChange
Log-likelihood value:                     -1067.99

------------------------
            Estimate
------------------------
pop_CL       0.13521
pop_V        8.0131
pop_tabs     0.57175
pop_lag      0.87544
pop_e0      96.401
pop_emax    -1.0614
pop_c50      1.4903
pop_tover   14.047
pk_Ω₁,₁      0.067972
pk_Ω₂,₂      0.021022
pk_Ω₃,₃      0.85627
pd_Ω₁,₁      0.002937
pd_Ω₂,₂      6.1888e-10
pd_Ω₃,₃      0.14607
pd_Ω₄,₄      0.01538
σ_prop       0.088485
σ_add        0.41684
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: 1.5974044799804688e-5
     1     5.174461e+05     8.708699e+05
 * time: 15.898103952407837
     2     3.865265e+05     6.344302e+05
 * time: 28.17545485496521
     3     1.804274e+05     2.829723e+05
 * time: 40.11125898361206
     4     9.706641e+04     1.550547e+05
 * time: 51.854007959365845
     5     4.769637e+04     6.778818e+04
 * time: 63.555351972579956
     6     2.902319e+04     3.499747e+04
 * time: 74.90209984779358
     7     1.823472e+04     1.705751e+04
 * time: 86.68490290641785
     8     1.258819e+04     9.569382e+03
 * time: 98.32494902610779
     9     9.389985e+03     8.615853e+03
 * time: 109.63489484786987
    10     7.314703e+03     7.636886e+03
 * time: 120.94653487205505
    11     5.916030e+03     6.624328e+03
 * time: 132.2332260608673
    12     4.930520e+03     5.558143e+03
 * time: 143.41965103149414
    13     4.125062e+03     4.315761e+03
 * time: 154.58531498908997
    14     3.549280e+03     3.051094e+03
 * time: 165.70467805862427
    15     3.283490e+03     2.157293e+03
 * time: 176.89147186279297
    16     3.204886e+03     1.659798e+03
 * time: 189.29878306388855
    17     3.194875e+03     1.480528e+03
 * time: 200.855406999588
    18     3.193944e+03     1.437922e+03
 * time: 212.81818985939026
    19     3.193070e+03     1.411186e+03
 * time: 224.7903380393982
    20     3.190129e+03     1.355327e+03
 * time: 236.7638840675354
    21     3.183228e+03     1.276603e+03
 * time: 248.43321585655212
    22     3.164897e+03     1.151838e+03
 * time: 259.87145495414734
    23     3.119250e+03     9.712652e+02
 * time: 271.33470392227173
    24     3.006297e+03     7.204344e+02
 * time: 283.2904279232025
    25     2.738913e+03     4.050546e+02
 * time: 294.9082729816437
    26     2.123834e+03     2.318194e+02
 * time: 306.10301303863525
    27     1.789142e+03     2.290466e+02
 * time: 318.26736402511597
    28     1.396456e+03     1.683975e+02
 * time: 352.17130398750305
    29     1.333545e+03     1.336198e+02
 * time: 365.8561999797821
    30     1.297773e+03     2.452181e+02
 * time: 376.06141996383667
    31     1.266002e+03     1.523972e+02
 * time: 386.21088194847107
    32     1.255505e+03     1.734000e+02
 * time: 396.3862578868866
    33     1.247788e+03     1.971637e+02
 * time: 407.4413709640503
    34     1.244490e+03     1.915744e+02
 * time: 418.0139729976654
    35     1.240568e+03     1.704280e+02
 * time: 428.72329902648926
    36     1.240502e+03     1.711813e+02
 * time: 438.84351897239685
    37     1.240491e+03     1.711683e+02
 * time: 449.12860584259033
    38     1.239992e+03     1.687296e+02
 * time: 459.46736693382263
    39     1.239200e+03     1.624744e+02
 * time: 469.61480689048767
    40     1.236975e+03     1.400443e+02
 * time: 479.8007159233093
    41     1.233209e+03     9.449763e+01
 * time: 490.24963092803955
    42     1.228687e+03     3.276923e+01
 * time: 500.48719906806946
    43     1.226467e+03     4.997214e+01
 * time: 510.705286026001
    44     1.226104e+03     4.905105e+01
 * time: 520.9492609500885
    45     1.226088e+03     4.676122e+01
 * time: 531.5824739933014
    46     1.226087e+03     4.628674e+01
 * time: 542.3007709980011
    47     1.226085e+03     4.541753e+01
 * time: 553.8191368579865
    48     1.226080e+03     4.403288e+01
 * time: 565.3386740684509
    49     1.226064e+03     4.143315e+01
 * time: 576.9147930145264
    50     1.226026e+03     3.664876e+01
 * time: 588.0051710605621
    51     1.225931e+03     2.851383e+01
 * time: 599.1053659915924
    52     1.225714e+03     2.844460e+01
 * time: 610.4080190658569
    53     1.225304e+03     3.025732e+01
 * time: 621.4817650318146
    54     1.224793e+03     4.151448e+01
 * time: 632.5708010196686
    55     1.224489e+03     5.047755e+01
 * time: 643.7071468830109
    56     1.224420e+03     4.452753e+01
 * time: 657.3773748874664
    57     1.224413e+03     3.994380e+01
 * time: 668.7143979072571
    58     1.224412e+03     3.879465e+01
 * time: 682.3529999256134
    59     1.224408e+03     3.677922e+01
 * time: 693.6922309398651
    60     1.224400e+03     3.379126e+01
 * time: 705.3743889331818
    61     1.224379e+03     3.158821e+01
 * time: 716.755863904953
    62     1.224324e+03     2.926306e+01
 * time: 728.3088529109955
    63     1.224181e+03     2.815869e+01
 * time: 739.8566608428955
    64     1.223815e+03     2.818300e+01
 * time: 751.2939560413361
    65     1.222911e+03     4.583041e+01
 * time: 762.9737560749054
    66     1.220921e+03     8.675281e+01
 * time: 774.2934608459473
    67     1.217625e+03     1.136294e+02
 * time: 785.4189839363098
    68     1.214324e+03     9.050245e+01
 * time: 796.6579079627991
    69     1.212536e+03     8.867180e+01
 * time: 807.8734059333801
    70     1.212272e+03     8.970655e+01
 * time: 818.9588489532471
    71     1.212263e+03     8.922293e+01
 * time: 831.8512239456177
    72     1.212259e+03     8.882951e+01
 * time: 843.568027973175
    73     1.212242e+03     8.761908e+01
 * time: 854.8586909770966
    74     1.212205e+03     8.562573e+01
 * time: 866.1403279304504
    75     1.212102e+03     8.125881e+01
 * time: 877.4882628917694
    76     1.211850e+03     7.230599e+01
 * time: 888.8495440483093
    77     1.211238e+03     5.323492e+01
 * time: 900.2711389064789
    78     1.209946e+03     7.373618e+01
 * time: 911.9688858985901
    79     1.207891e+03     8.401772e+01
 * time: 923.422544002533
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Warning: Terminated early due to NaN in gradient.
@ Optim ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/Optim/mv9zc/src/multivariate/optimize/optimize.jl:136
Warning: Terminated early due to NaN in gradient.
@ Optim ~/run/_work/PumasTutorials.jl/PumasTutorials.jl/custom_julia_depot/packages/Optim/mv9zc/src/multivariate/optimize/optimize.jl:136
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 * time: 3571.674206018448
   312     1.068374e+03     1.284631e+00
 * time: 3586.224410057068
   313     1.068374e+03     1.277430e+00
 * time: 3597.3031129837036
   314     1.068374e+03     1.278342e+00
 * time: 3608.1831319332123
   315     1.068374e+03     1.278561e+00
 * time: 3620.496243953705
   316     1.068374e+03     1.278598e+00
 * time: 3632.927733898163
   317     1.068374e+03     1.278765e+00
 * time: 3645.5450649261475
   318     1.068374e+03     1.278767e+00
 * time: 3658.835216999054
   319     1.068374e+03     1.283325e+00
 * time: 3670.0238959789276
   320     1.068374e+03     1.284455e+00
 * time: 3681.32239985466
   321     1.068374e+03     1.297288e+00
 * time: 3693.6294519901276
   322     1.068373e+03     1.309277e+00
 * time: 3706.1950368881226
   323     1.068370e+03     1.327095e+00
 * time: 3718.5782659053802
   324     1.068363e+03     1.340822e+00
 * time: 3730.64324593544
   325     1.068345e+03     1.329791e+00
 * time: 3742.3253350257874
   326     1.068304e+03     1.440802e+00
 * time: 3754.1032960414886
   327     1.068220e+03     1.781108e+00
 * time: 3766.8922169208527
   328     1.068100e+03     1.555010e+00
 * time: 3783.205395936966
   329     1.068015e+03     6.383597e-01
 * time: 3798.17605304718
   330     1.068000e+03     4.313404e-02
 * time: 3814.4858660697937
   331     1.067999e+03     1.160644e-01
 * time: 3846.432205915451
   332     1.067998e+03     1.891364e-01
 * time: 3870.0866589546204
   333     1.067995e+03     2.072805e-01
 * time: 3889.680629968643
   334     1.067993e+03     1.268387e-01
 * time: 3914.831162929535
   335     1.067992e+03     7.307859e-02
 * time: 3942.960671901703
   336     1.067991e+03     8.280285e-02
 * time: 3970.462466955185
   337     1.067991e+03     8.863498e-02
 * time: 3992.5110199451447
   338     1.067991e+03     9.334675e-02
 * time: 4019.1770708560944
   339     1.067991e+03     9.512481e-02
 * time: 4041.4833109378815
   340     1.067991e+03     9.522332e-02
 * time: 4061.150853872299
   341     1.067991e+03     9.513094e-02
 * time: 4080.4553508758545
   342     1.067991e+03     9.508043e-02
 * time: 4099.755939006805
   343     1.067991e+03     9.508043e-02
 * time: 4129.840872049332
   344     1.067991e+03     9.508043e-02
 * time: 4159.801071882248
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:                   -1067.9914

-----------------------
            Estimate
-----------------------
pop_CL       0.13521
pop_V        8.0133
pop_tabs     0.57109
pop_lag      0.87562
pop_e0      96.399
pop_emax    -1.0615
pop_c50      1.4912
pop_tover   14.05
pk_Ω₁,₁      0.068013
pk_Ω₂,₂      0.021048
pk_Ω₃,₃      0.86269
pd_Ω₁,₁      0.0029772
pd_Ω₂,₂      1.9506e-7
pd_Ω₃,₃      0.14561
pd_Ω₄,₄      0.015351
σ_prop       0.088485
σ_add        0.41684
σ_fx         3.5803
-----------------------

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: 7.104873657226562e-5
     1     5.174461e+05     8.708698e+05
 * time: 7.322011947631836
     2     3.865265e+05     6.344302e+05
 * time: 10.60608696937561
     3     1.804274e+05     2.829723e+05
 * time: 13.33290696144104
     4     9.706640e+04     1.550547e+05
 * time: 16.0142719745636
     5     4.769637e+04     6.778818e+04
 * time: 19.362586975097656
     6     2.902319e+04     3.499747e+04
 * time: 22.591015100479126
     7     1.823472e+04     1.705751e+04
 * time: 25.403118133544922
     8     1.258819e+04     9.569381e+03
 * time: 27.69648814201355
     9     9.389984e+03     8.615851e+03
 * time: 30.47625994682312
    10     7.314702e+03     7.636883e+03
 * time: 32.61696910858154
    11     5.916029e+03     6.624325e+03
 * time: 34.45844316482544
    12     4.930519e+03     5.558140e+03
 * time: 36.259063959121704
    13     4.125060e+03     4.315759e+03
 * time: 38.07671809196472
    14     3.549280e+03     3.051093e+03
 * time: 40.018845081329346
    15     3.283489e+03     2.157292e+03
 * time: 43.03418207168579
    16     3.204886e+03     1.659798e+03
 * time: 44.89914608001709
    17     3.194875e+03     1.480528e+03
 * time: 46.743937969207764
    18     3.193944e+03     1.437921e+03
 * time: 48.554309129714966
    19     3.193070e+03     1.411186e+03
 * time: 50.09391403198242
    20     3.190129e+03     1.355327e+03
 * time: 51.664677143096924
    21     3.183228e+03     1.276603e+03
 * time: 53.4485399723053
    22     3.164897e+03     1.151838e+03
 * time: 55.01418709754944
    23     3.119250e+03     9.712651e+02
 * time: 56.50082802772522
    24     3.006297e+03     7.204342e+02
 * time: 57.973029136657715
    25     2.738913e+03     4.050545e+02
 * time: 59.43356800079346
    26     2.123834e+03     2.318194e+02
 * time: 60.85251808166504
    27     1.789139e+03     2.290465e+02
 * time: 62.382508993148804
    28     1.396455e+03     1.683969e+02
 * time: 338.58069801330566
    29     1.333545e+03     1.336195e+02
 * time: 340.07842898368835
    30     1.297771e+03     2.452175e+02
 * time: 341.3870310783386
    31     1.266002e+03     1.523957e+02
 * time: 342.6874141693115
    32     1.255506e+03     1.733982e+02
 * time: 344.049742937088
    33     1.247789e+03     1.971613e+02
 * time: 345.4190671443939
    34     1.244490e+03     1.915717e+02
 * time: 346.79066705703735
    35     1.240568e+03     1.704241e+02
 * time: 348.1394350528717
    36     1.240503e+03     1.711777e+02
 * time: 349.95986008644104
    37     1.240492e+03     1.711647e+02
 * time: 352.6663751602173
    38     1.239992e+03     1.687233e+02
 * time: 354.3270959854126
    39     1.239199e+03     1.624614e+02
 * time: 355.6788671016693
    40     1.236972e+03     1.400083e+02
 * time: 357.0054359436035
    41     1.233204e+03     9.443139e+01
 * time: 358.3349151611328
    42     1.228683e+03     3.274305e+01
 * time: 359.63933205604553
    43     1.226466e+03     4.997666e+01
 * time: 360.93474817276
    44     1.226104e+03     4.904455e+01
 * time: 362.24123215675354
    45     1.226088e+03     4.675831e+01
 * time: 363.6303119659424
    46     1.226088e+03     4.628481e+01
 * time: 365.3394031524658
    47     1.226085e+03     4.541370e+01
 * time: 366.8299069404602
    48     1.226080e+03     4.402775e+01
 * time: 368.34204506874084
    49     1.226064e+03     4.142396e+01
 * time: 369.6363260746002
    50     1.226026e+03     3.663267e+01
 * time: 370.91848516464233
    51     1.225931e+03     2.851376e+01
 * time: 372.24897503852844
    52     1.225714e+03     2.844439e+01
 * time: 373.5399830341339
    53     1.225303e+03     3.026353e+01
 * time: 374.8348729610443
    54     1.224791e+03     4.156415e+01
 * time: 376.14160203933716
    55     1.224489e+03     5.047549e+01
 * time: 377.4842300415039
    56     1.224420e+03     4.451326e+01
 * time: 378.80538296699524
    57     1.224413e+03     3.994115e+01
 * time: 380.0817151069641
    58     1.224412e+03     3.879491e+01
 * time: 381.39754915237427
    59     1.224408e+03     3.677379e+01
 * time: 382.7563591003418
    60     1.224400e+03     3.378181e+01
 * time: 384.00221705436707
    61     1.224379e+03     3.158275e+01
 * time: 385.2209300994873
    62     1.224324e+03     2.925310e+01
 * time: 386.4209420681
    63     1.224181e+03     2.815884e+01
 * time: 387.6277930736542
    64     1.223813e+03     2.818297e+01
 * time: 388.8539710044861
    65     1.222906e+03     4.596708e+01
 * time: 390.1006691455841
    66     1.220911e+03     8.689986e+01
 * time: 391.3998830318451
    67     1.217611e+03     1.136509e+02
 * time: 392.6542570590973
    68     1.214314e+03     9.033016e+01
 * time: 393.9196310043335
    69     1.212533e+03     8.868756e+01
 * time: 395.17840600013733
    70     1.212272e+03     8.970398e+01
 * time: 396.4440779685974
    71     1.212263e+03     8.922046e+01
 * time: 397.7041699886322
    72     1.212259e+03     8.882520e+01
 * time: 398.93148016929626
    73     1.212242e+03     8.761642e+01
 * time: 400.16118812561035
    74     1.212205e+03     8.562156e+01
 * time: 401.3679349422455
    75     1.212102e+03     8.125479e+01
 * time: 402.5924940109253
    76     1.211850e+03     7.229855e+01
 * time: 403.8267090320587
    77     1.211238e+03     5.322149e+01
 * time: 405.06081795692444
    78     1.209945e+03     7.377053e+01
 * time: 406.3185441493988
    79     1.207890e+03     8.403807e+01
 * time: 407.5897891521454
    80     1.206058e+03     9.147814e+01
 * time: 408.83907294273376
    81     1.205389e+03     9.689402e+01
 * time: 410.0869851112366
    82     1.205303e+03     8.594641e+01
 * time: 411.3467011451721
    83     1.205297e+03     8.262863e+01
 * time: 412.5811331272125
    84     1.205292e+03     8.096275e+01
 * time: 413.81771516799927
    85     1.205277e+03     7.747512e+01
 * time: 415.06894516944885
    86     1.205241e+03     7.259152e+01
 * time: 416.33504009246826
    87     1.205143e+03     6.664782e+01
 * time: 417.5940930843353
    88     1.204895e+03     6.374591e+01
 * time: 418.84223794937134
    89     1.204267e+03     5.753713e+01
 * time: 420.08252811431885
    90     1.202818e+03     4.866654e+01
 * time: 421.3129839897156
    91     1.200116e+03     5.085943e+01
 * time: 422.53071117401123
    92     1.196895e+03     7.139637e+01
 * time: 423.7651741504669
    93     1.194610e+03     4.693841e+01
 * time: 425.00068402290344
    94     1.193880e+03     4.874622e+01
 * time: 426.23438715934753
    95     1.193833e+03     4.997328e+01
 * time: 427.4524190425873
    96     1.193831e+03     5.008739e+01
 * time: 428.65587997436523
    97     1.193829e+03     5.014847e+01
 * time: 429.863765001297
    98     1.193824e+03     5.025182e+01
 * time: 431.0715069770813
    99     1.193812e+03     5.040232e+01
 * time: 432.300164937973
   100     1.193778e+03     5.061917e+01
 * time: 433.52180194854736
   101     1.193693e+03     5.087902e+01
 * time: 434.73760294914246
   102     1.193472e+03     5.105102e+01
 * time: 435.9562621116638
   103     1.192926e+03     5.068588e+01
 * time: 437.18855714797974
   104     1.191681e+03     4.863506e+01
 * time: 438.707643032074
   105     1.189351e+03     4.892935e+01
 * time: 440.2760601043701
   106     1.186420e+03     7.777156e+01
 * time: 441.70265102386475
   107     1.184527e+03     8.874260e+01
 * time: 443.495502948761
   108     1.184034e+03     8.377283e+01
 * time: 444.86984610557556
   109     1.183978e+03     7.932657e+01
 * time: 446.2077419757843
   110     1.183969e+03     7.794290e+01
 * time: 447.5452570915222
   111     1.183966e+03     7.787253e+01
 * time: 448.86284708976746
   112     1.183962e+03     7.833696e+01
 * time: 450.1385340690613
   113     1.183955e+03     7.929137e+01
 * time: 451.40823912620544
   114     1.183940e+03     8.084179e+01
 * time: 452.68625497817993
   115     1.183904e+03     8.331129e+01
 * time: 453.9645850658417
   116     1.183812e+03     8.698526e+01
 * time: 455.2387070655823
   117     1.183576e+03     9.189102e+01
 * time: 456.66962003707886
   118     1.182997e+03     9.669181e+01
 * time: 458.43975710868835
   119     1.181703e+03     9.636170e+01
 * time: 460.43154311180115
   120     1.179436e+03     8.062012e+01
 * time: 462.1261610984802
   121     1.177026e+03     4.572956e+01
 * time: 464.17199206352234
   122     1.175794e+03     1.863503e+01
 * time: 465.75620198249817
   123     1.175474e+03     1.968076e+01
 * time: 467.34851598739624
   124     1.175429e+03     1.958612e+01
 * time: 468.6600720882416
   125     1.175427e+03     1.993705e+01
 * time: 469.90992999076843
   126     1.175426e+03     1.962015e+01
 * time: 471.1441960334778
   127     1.175426e+03     1.965820e+01
 * time: 472.35232615470886
   128     1.175424e+03     1.984461e+01
 * time: 473.5755729675293
   129     1.175421e+03     2.001158e+01
 * time: 474.7871689796448
   130     1.175413e+03     2.035215e+01
 * time: 476.02071595191956
   131     1.175392e+03     2.084316e+01
 * time: 477.2937390804291
   132     1.175336e+03     2.164622e+01
 * time: 478.5766670703888
   133     1.175189e+03     2.287922e+01
 * time: 479.876620054245
   134     1.174802e+03     2.475497e+01
 * time: 481.1645390987396
   135     1.173793e+03     4.143173e+01
 * time: 482.4516761302948
   136     1.171222e+03     7.150973e+01
 * time: 483.79141998291016
   137     1.165149e+03     1.078889e+02
 * time: 485.1463420391083
   138     1.155085e+03     7.759079e+01
 * time: 486.54389905929565
   139     1.149213e+03     6.862147e+01
 * time: 487.9636631011963
   140     1.146917e+03     6.326660e+01
 * time: 489.36150312423706
   141     1.144667e+03     4.997043e+01
 * time: 490.7516601085663
   142     1.143086e+03     2.541688e+01
 * time: 492.1372699737549
   143     1.141825e+03     1.975967e+01
 * time: 493.5308539867401
   144     1.141293e+03     2.050313e+01
 * time: 495.20981907844543
   145     1.141050e+03     2.076852e+01
 * time: 496.5557770729065
   146     1.140979e+03     2.090534e+01
 * time: 497.88265109062195
   147     1.140976e+03     2.094562e+01
 * time: 499.17533016204834
   148     1.140975e+03     2.099640e+01
 * time: 500.53579902648926
   149     1.140974e+03     2.099904e+01
 * time: 501.86027097702026
   150     1.140974e+03     2.099888e+01
 * time: 503.15537905693054
   151     1.140973e+03     2.099225e+01
 * time: 504.4419529438019
   152     1.140972e+03     2.098193e+01
 * time: 505.7398681640625
   153     1.140970e+03     2.096599e+01
 * time: 507.0298330783844
   154     1.140963e+03     2.094403e+01
 * time: 508.3318610191345
   155     1.140947e+03     2.091801e+01
 * time: 509.6566300392151
   156     1.140905e+03     2.090038e+01
 * time: 510.99618315696716
   157     1.140796e+03     2.093557e+01
 * time: 512.2999160289764
   158     1.140506e+03     2.115931e+01
 * time: 513.6281220912933
   159     1.139721e+03     2.222025e+01
 * time: 514.9414229393005
   160     1.137501e+03     3.402235e+01
 * time: 516.2908430099487
   161     1.132295e+03     5.964360e+01
 * time: 517.7062561511993
   162     1.130015e+03     6.884174e+01
 * time: 519.2942559719086
   163     1.128409e+03     7.427016e+01
 * time: 521.03830909729
   164     1.126418e+03     1.090718e+02
 * time: 522.7275431156158
   165     1.120677e+03     1.368046e+02
 * time: 524.221449136734
   166     1.116323e+03     7.460477e+01
 * time: 525.712671995163
   167     1.115215e+03     4.213911e+01
 * time: 527.095899105072
   168     1.112605e+03     3.600062e+01
 * time: 528.5502309799194
   169     1.111487e+03     1.610038e+01
 * time: 529.9962291717529
   170     1.111244e+03     1.728118e+01
 * time: 531.5100910663605
   171     1.111202e+03     1.118677e+01
 * time: 533.0346319675446
   172     1.111188e+03     1.043946e+01
 * time: 534.6022341251373
   173     1.111187e+03     1.049047e+01
 * time: 536.149069070816
   174     1.111187e+03     1.060113e+01
 * time: 537.6814429759979
   175     1.111187e+03     1.073318e+01
 * time: 539.1848709583282
   176     1.111186e+03     1.091776e+01
 * time: 540.6622109413147
   177     1.111185e+03     1.120485e+01
 * time: 542.1194319725037
   178     1.111182e+03     1.164897e+01
 * time: 543.6381599903107
   179     1.111175e+03     1.235086e+01
 * time: 545.1864500045776
   180     1.111156e+03     1.346373e+01
 * time: 546.7297320365906
   181     1.111106e+03     1.523550e+01
 * time: 548.3317589759827
   182     1.110975e+03     2.101852e+01
 * time: 549.8883471488953
   183     1.110636e+03     3.414945e+01
 * time: 551.4514260292053
   184     1.109781e+03     5.437237e+01
 * time: 552.9651920795441
   185     1.107753e+03     8.206728e+01
 * time: 554.4822111129761
   186     1.103621e+03     1.078177e+02
 * time: 556.0557961463928
   187     1.097552e+03     1.003149e+02
 * time: 557.7079930305481
   188     1.092961e+03     5.085501e+01
 * time: 559.4252879619598
   189     1.091993e+03     1.581003e+01
 * time: 561.1560349464417
   190     1.091933e+03     5.097237e+00
 * time: 562.8819479942322
   191     1.091917e+03     4.300956e+00
 * time: 564.6025371551514
   192     1.091912e+03     4.320223e+00
 * time: 566.2926261425018
   193     1.091907e+03     4.348370e+00
 * time: 568.009327173233
   194     1.091905e+03     4.353097e+00
 * time: 569.7150361537933
   195     1.091904e+03     4.346022e+00
 * time: 571.4347140789032
   196     1.091904e+03     4.343155e+00
 * time: 573.1293139457703
   197     1.091904e+03     4.341664e+00
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   198     1.091904e+03     4.340195e+00
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   199     1.091904e+03     4.336213e+00
 * time: 578.1894090175629
   200     1.091904e+03     4.330311e+00
 * time: 579.9176950454712
   201     1.091903e+03     4.319607e+00
 * time: 581.6340651512146
   202     1.091901e+03     4.301544e+00
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   203     1.091897e+03     4.269481e+00
 * time: 585.0375239849091
   204     1.091884e+03     4.211434e+00
 * time: 586.755481004715
   205     1.091853e+03     4.101559e+00
 * time: 588.4777920246124
   206     1.091773e+03     5.308614e+00
 * time: 590.2596340179443
   207     1.091575e+03     8.247123e+00
 * time: 592.1643640995026
   208     1.091124e+03     1.189112e+01
 * time: 594.0769691467285
   209     1.090247e+03     1.469556e+01
 * time: 596.0119199752808
   210     1.088870e+03     1.380917e+01
 * time: 597.9012830257416
   211     1.087426e+03     8.335656e+00
 * time: 599.671019077301
   212     1.087110e+03     5.812129e+00
 * time: 601.2788410186768
   213     1.087046e+03     5.486140e+00
 * time: 602.9283709526062
   214     1.087043e+03     5.387943e+00
 * time: 604.5629870891571
   215     1.087043e+03     5.384086e+00
 * time: 606.175400018692
   216     1.087043e+03     5.384659e+00
 * time: 607.8076190948486
   217     1.087043e+03     5.384004e+00
 * time: 609.4403729438782
   218     1.087043e+03     5.383774e+00
 * time: 611.08451795578
   219     1.087043e+03     5.383930e+00
 * time: 612.7288601398468
   220     1.087043e+03     5.384561e+00
 * time: 614.3363239765167
   221     1.087042e+03     5.386374e+00
 * time: 615.9548239707947
   222     1.087042e+03     5.390542e+00
 * time: 617.5462739467621
   223     1.087039e+03     5.400702e+00
 * time: 619.1603081226349
   224     1.087034e+03     5.425538e+00
 * time: 620.7731921672821
   225     1.087019e+03     5.488503e+00
 * time: 622.4314429759979
   226     1.086979e+03     6.767456e+00
 * time: 624.010458946228
   227     1.086869e+03     1.111794e+01
 * time: 625.6370301246643
   228     1.086511e+03     1.832672e+01
 * time: 627.2265830039978
   229     1.085576e+03     2.156837e+01
 * time: 628.9837400913239
   230     1.085227e+03     2.018423e+01
 * time: 630.6900150775909
   231     1.084517e+03     2.676799e+01
 * time: 632.5078129768372
   232     1.083377e+03     3.273606e+01
 * time: 634.047247171402
   233     1.076509e+03     8.610449e+01
 * time: 635.5874559879303
   234     1.074485e+03     3.376716e+01
 * time: 637.1121289730072
   235     1.073053e+03     4.695023e+01
 * time: 638.6318600177765
   236     1.070621e+03     3.730659e+01
 * time: 640.1557400226593
   237     1.070168e+03     1.851969e+01
 * time: 641.7508859634399
   238     1.069604e+03     8.653854e+00
 * time: 643.296373128891
   239     1.069503e+03     6.575696e+00
 * time: 644.8002591133118
   240     1.069489e+03     2.201319e+00
 * time: 646.2935690879822
   241     1.069488e+03     2.222225e+00
 * time: 647.7778141498566
   242     1.069488e+03     2.233015e+00
 * time: 649.2536900043488
   243     1.069488e+03     2.235520e+00
 * time: 650.7262279987335
   244     1.069488e+03     2.236537e+00
 * time: 652.236289024353
   245     1.069488e+03     2.238738e+00
 * time: 653.7871301174164
   246     1.069488e+03     2.241896e+00
 * time: 655.2830879688263
   247     1.069488e+03     2.247133e+00
 * time: 656.7732360363007
   248     1.069488e+03     2.255198e+00
 * time: 658.281965970993
   249     1.069487e+03     2.267660e+00
 * time: 659.8070650100708
   250     1.069486e+03     2.285977e+00
 * time: 661.3415529727936
   251     1.069484e+03     2.310925e+00
 * time: 662.8783710002899
   252     1.069477e+03     2.338791e+00
 * time: 664.4251520633698
   253     1.069460e+03     2.462053e+00
 * time: 665.9447700977325
   254     1.069419e+03     3.836663e+00
 * time: 667.4696900844574
   255     1.069328e+03     5.485698e+00
 * time: 668.9939179420471
   256     1.069172e+03     6.352821e+00
 * time: 670.5864169597626
   257     1.069009e+03     4.354133e+00
 * time: 672.1830821037292
   258     1.068940e+03     1.469908e+00
 * time: 673.7821960449219
   259     1.068930e+03     8.676381e-01
 * time: 675.3799011707306
   260     1.068929e+03     8.686821e-01
 * time: 676.9657731056213
   261     1.068929e+03     8.689170e-01
 * time: 678.5497260093689
   262     1.068929e+03     8.689496e-01
 * time: 680.1364030838013
   263     1.068929e+03     8.689496e-01
 * time: 682.109493970871
   264     1.068929e+03     8.689680e-01
 * time: 683.8309669494629
   265     1.068929e+03     8.689680e-01
 * time: 685.8362181186676
   266     1.068929e+03     8.689680e-01
 * time: 687.9968740940094
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:              NoObjectiveChange
Log-likelihood value:                   -1068.9294

------------------------
            Estimate
------------------------
pop_CL       0.13521
pop_V        8.0112
pop_tabs     0.56617
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      0.020319
pk_Ω₃,₃      0.89959
pd_Ω₁,₁      0.0028777
pd_Ω₂,₂      0.00044805
pd_Ω₃,₃      0.15376
pd_Ω₄,₄      0.015013
σ_prop       0.088937
σ_add        0.41485
σ_fx         3.5814
------------------------

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.