StateRate.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/StateRate.h"
#include "neml2/tensors/SSR4.h"
 
namespace neml2
{
register_NEML2_object(ScalarStateRate);
register_NEML2_object(SR2StateRate);
 
template <typename T>
OptionSet
StateRate<T>::expected_options()
{
  OptionSet options = Model::expected_options();
  options.doc() = "Calculate the first order discrete time derivative of a state variable as \\f$ "
                  "\\dot{s} = \\frac{s-s_n}{t-t_n} \\f$, where \\f$ s \\f$ is the state variable, "
                  "and \\f$ t \\f$ is time.";
 
  options.set<VariableName>("state");
  options.set("state").doc() = "The state variable to take time derivative with";
 
  options.set<VariableName>("time") = VariableName("t");
  options.set("time").doc() = "Time";
 
  return options;
}
 
template <typename T>
StateRate<T>::StateRate(const OptionSet & options)
  : Model(options),
    _s(declare_input_variable<T>(options.get<VariableName>("state").on("state"))),
    _sn(declare_input_variable<T>(options.get<VariableName>("state").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"))),
    _ds_dt(declare_output_variable<T>(
        options.get<VariableName>("state").with_suffix("_rate").on("state")))
{
}
 
template <typename T>
void
StateRate<T>::set_value(bool out, bool dout_din, bool d2out_din2)
{
  auto ds = _s - _sn;
  auto dt = _t - _tn;
 
  if (out)
    _ds_dt = ds / dt;
 
  if (dout_din || d2out_din2)
  {
    auto I = T::identity_map(options());
 
    if (dout_din)
    {
      _ds_dt.d(_s) = I / dt;
      _ds_dt.d(_sn) = -I / dt;
      _ds_dt.d(_t) = -ds / dt / dt;
      _ds_dt.d(_tn) = ds / dt / dt;
    }
 
    if (d2out_din2)
    {
      _ds_dt.d(_s, _t) = -I / dt / dt;
      _ds_dt.d(_s, _tn) = I / dt / dt;
 
      _ds_dt.d(_sn, _t) = I / dt / dt;
      _ds_dt.d(_sn, _tn) = -I / dt / dt;
 
      _ds_dt.d(_t, _s) = -I / dt / dt;
      _ds_dt.d(_t, _sn) = I / dt / dt;
      _ds_dt.d(_t, _t) = 2 * ds / dt / dt / dt;
      _ds_dt.d(_t, _tn) = -2 * ds / dt / dt / dt;
 
      _ds_dt.d(_tn, _s) = I / dt / dt;
      _ds_dt.d(_tn, _sn) = -I / dt / dt;
      _ds_dt.d(_tn, _t) = -2 * ds / dt / dt / dt;
      _ds_dt.d(_tn, _tn) = 2 * ds / dt / dt / dt;
    }
  }
}
 
template class StateRate<Scalar>;
template class StateRate<SR2>;
} // namespace neml2