ForwardEulerTimeIntegration.cxx

// Copyright 2023, UChicago Argonne, LLC
// All Rights Reserved
// Software Name: NEML2 -- the New Engineering material Model Library, version 2
// By: Argonne National Laboratory
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#include "neml2/models/ForwardEulerTimeIntegration.h"
#include "neml2/tensors/SSR4.h"
 
namespace neml2
{
register_NEML2_object(ScalarForwardEulerTimeIntegration);
register_NEML2_object(SR2ForwardEulerTimeIntegration);
 
template <typename T>
OptionSet
ForwardEulerTimeIntegration<T>::expected_options()
{
  OptionSet options = Model::expected_options();
  options.doc() =
      "Perform forward Euler time integration defined as \\f$ s = s_n + (t - t_n) \\dot{s} "
      "\\f$, where \\f$s\\f$ is the variable being integrated, \\f$\\dot{s}\\f$ is the variable "
      "rate, and \\f$t\\f$ is time. Subscripts \\f$n\\f$ denote quantities from the previous time "
      "step.";
 
  options.set<VariableName>("variable");
  options.set("variable").doc() = "Variable being integrated";
 
  options.set<VariableName>("time") = VariableName("t");
  options.set("time").doc() = "Time";
 
  return options;
}
 
template <typename T>
ForwardEulerTimeIntegration<T>::ForwardEulerTimeIntegration(const OptionSet & options)
  : Model(options),
    _var_name(options.get<VariableName>("variable")),
    _var_rate_name(_var_name.with_suffix("_rate")),
    _s(declare_output_variable<T>(_var_name.on("state"))),
    _ds_dt(declare_input_variable<T>(_var_rate_name.on("state"))),
    _sn(declare_input_variable<T>(_var_name.on("old_state"))),
    _t(declare_input_variable<Scalar>(options.get<VariableName>("time").on("forces"))),
    _tn(declare_input_variable<Scalar>(options.get<VariableName>("time").on("old_forces")))
{
}
 
template <typename T>
void
ForwardEulerTimeIntegration<T>::set_value(bool out, bool dout_din, bool d2out_din2)
{
  if (out)
    _s = _sn + _ds_dt * (_t - _tn);
 
  if (dout_din || d2out_din2)
  {
    auto I = T::identity_map(options());
 
    if (dout_din)
    {
      _s.d(_ds_dt) = I * (_t - _tn);
      if (Model::stage == Model::Stage::UPDATING)
      {
        _s.d(_sn) = I;
        _s.d(_t) = _ds_dt;
        _s.d(_tn) = -_ds_dt;
      }
    }
 
    if (d2out_din2)
      if (Model::stage == Model::Stage::UPDATING)
      {
        _s.d(_ds_dt, _t) = I;
        _s.d(_ds_dt, _tn) = -I;
        _s.d(_t, _ds_dt) = I;
        _s.d(_tn, _ds_dt) = -I;
      }
  }
}
 
template class ForwardEulerTimeIntegration<Scalar>;
template class ForwardEulerTimeIntegration<SR2>;
} // namespace neml2