MixedControlSetup.cxx

// Copyright 2023, UChicago Argonne, LLC
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// Software Name: NEML2 -- the New Engineering material Model Library, version 2
// By: Argonne National Laboratory
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#include "neml2/models/solid_mechanics/MixedControlSetup.h"
#include "neml2/misc/math.h"
 
namespace neml2
{
register_NEML2_object(MixedControlSetup);
 
OptionSet
MixedControlSetup::expected_options()
{
  OptionSet options = Model::expected_options();
  options.doc() =
      "Object to setup a model for mixed stress/strain control.  Copies the values of the "
      "fixed_values (the input strain or stress) and the mixed_state (the conjugate stress or "
      "strain values) into the stress and strain tensors used by the model.";
 
  options.set<VariableName>("control") = VariableName("forces", "control");
  options.set("control").doc() =
      "The name of the control signal.  Values less than the threshold are "
      "strain control, greater are stress control";
 
  options.set<CrossRef<BatchTensor>>("threshold") = "0.5";
  options.set("threshold").doc() = "The threshold to switch between strain and stress control";
 
  options.set<VariableName>("mixed_state") = VariableName("state", "mixed_state");
  options.set("mixed_state").doc() = "The name of the mixed state tensor. This holds the conjugate "
                                     "values to those being controlled";
 
  options.set<VariableName>("fixed_values") = VariableName("forces", "fixed_values");
  options.set("fixed_values").doc() = "The name of the fixed values, i.e. the actual strain or "
                                      "stress values being imposed on the model";
 
  options.set<VariableName>("cauchy_stress") = VariableName("state", "S");
  options.set("cauchy_stress").doc() = "The name of the Cauchy stress tensor";
 
  options.set<VariableName>("strain") = VariableName("forces", "E");
  options.set("strain").doc() = "The name of the strain tensor";
 
  return options;
}
 
MixedControlSetup::MixedControlSetup(const OptionSet & options)
  : Model(options),
    _threshold(options.get<CrossRef<BatchTensor>>("threshold")),
    _control(declare_input_variable<SR2>("control")),
    _fixed_values(declare_input_variable<SR2>("fixed_values")),
    _mixed_state(declare_input_variable<SR2>("mixed_state")),
    _stress(declare_output_variable<SR2>("cauchy_stress")),
    _strain(declare_output_variable<SR2>("strain"))
{
}
 
void
MixedControlSetup::set_value(bool out, bool dout_din, bool d2out_din2)
{
  auto [dstrain, dstress] = make_operators(_control.tensor());
 
  if (out)
  {
    // Even benign in place operations get errors
    _stress = dstress * _fixed_values + dstrain * _mixed_state;
    _strain = dstrain * _fixed_values + dstress * _mixed_state;
  }
 
  if (dout_din)
  {
    _stress.d(_fixed_values) = dstress;
    _stress.d(_mixed_state) = dstrain;
 
    _strain.d(_fixed_values) = dstrain;
    _strain.d(_mixed_state) = dstress;
  }
 
  // All zero
  (void)(d2out_din2);
}
 
std::pair<SSR4, SSR4>
MixedControlSetup::make_operators(const SR2 & control) const
{
  auto strain_select = control <= _threshold;
  auto stress_select = control > _threshold;
 
  // This also converts these to floats
  auto ones_stress = BatchTensor(strain_select.to(_stress.tensor().options()), control.batch_dim());
  auto ones_strain = BatchTensor::ones_like(control) - ones_stress;
 
  // auto dstrain = SSR4(BatchTensor(torch::diag_embed(ones_stress), batch_dim()));
  auto dstrain = math::base_diag_embed(ones_stress);
  auto dstress = math::base_diag_embed(ones_strain);
 
  return {dstrain, dstress};
}
 
} // namespace neml2