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merge residual and jacobian calculation
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@bobmyhill
bobmyhill committed Jun 5, 2024
1 parent 26cfcc0 commit 97d618f
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Showing 2 changed files with 43 additions and 73 deletions.
29 changes: 8 additions & 21 deletions include/aspect/material_model/rheology/diffusion_dislocation.h
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Original file line number Diff line number Diff line change
Expand Up @@ -90,32 +90,19 @@ namespace aspect
const double temperature,
const SymmetricTensor<2,dim> &strain_rate) const;

/**
* Compute the derivative of the natural logarithm of the strain rate
* with respect to the natural logarithm of the stress
* at the current evaluation point (log stress) estimated by KINSOL.
*/
void
compute_log_strain_rate_deriv(const Vector<double> &evaluation_point,
double pressure,
double temperature,
const Rheology::DiffusionCreepParameters diffusion_creep_parameters,
const Rheology::DislocationCreepParameters dislocation_creep_parameters,
double &log_strain_rate_deriv) const;

/**
* Compute the residual of the natural logarithm of the strain rate
* at the current evaluation point (log stress) estimated by KINSOL.
* and the derivative with respect to the logarithm of the stress
* at the current value of the logarithm of the stress.
*/
void
compute_log_strain_rate_residual(
const Vector<double> &evaluation_point,
Vector<double> &residual,
double pressure,
double temperature,
std::pair<double, double>
compute_log_strain_rate_residual_and_derivative(
const double current_log_stress_ii,
const double pressure,
const double temperature,
const Rheology::DiffusionCreepParameters diffusion_creep_parameters,
const Rheology::DislocationCreepParameters dislocation_creep_parameters,
double log_edot_ii) const;
const double log_edot_ii) const;

/**
* Compute the viscosity based on the composite viscous creep law,
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87 changes: 35 additions & 52 deletions source/material_model/rheology/diffusion_dislocation.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -80,20 +80,11 @@ namespace aspect
(constants::gas_constant*temperature));

// Because the ratios of the diffusion and dislocation strain rates are not known, stress is also unknown
// We use KINSOL to find the second invariant of the stress tensor.
// Start with the assumption that all strain is accommodated by diffusion creep:
// If the diffusion creep prefactor is very small, that means that the diffusion viscosity is very large.
// In this case, use the maximum viscosity instead to compute the starting guess.
double stress_ii = (prefactor_stress_diffusion > (0.5 / maximum_viscosity)
?
edot_ii/prefactor_stress_diffusion
:
0.5 / maximum_viscosity);
Vector<double> log_stress_ii(1);
log_stress_ii[0] = std::log(stress_ii);

typename SUNDIALS::KINSOL<Vector<double>>::AdditionalData additional_data;
// We use KINSOL to find the second invariant of the stress tensor that satisfies the total strain rate.
SUNDIALS::KINSOL<Vector<double>>::AdditionalData additional_data;
additional_data.function_tolerance = log_strain_rate_residual_threshold;
additional_data.maximum_non_linear_iterations = stress_max_iteration_number;
additional_data.maximum_setup_calls = 1;

SUNDIALS::KINSOL<Vector<double>> nonlinear_solver(additional_data);

Expand All @@ -103,74 +94,66 @@ namespace aspect
};

nonlinear_solver.residual =
[&](const Vector<double> &evaluation_point,
[&](const Vector<double> &current_log_stress_ii,
Vector<double> &residual)
{
compute_log_strain_rate_residual(evaluation_point, residual, pressure, temperature, diffusion_creep_parameters, dislocation_creep_parameters, log_edot_ii);
std::tie(residual(0), log_strain_rate_deriv) = compute_log_strain_rate_residual_and_derivative(current_log_stress_ii[0], pressure, temperature, diffusion_creep_parameters, dislocation_creep_parameters, log_edot_ii);
};

nonlinear_solver.setup_jacobian =
[&](const Vector<double> &current_u,
[&](const Vector<double> & /*current_log_stress_ii*/,
const Vector<double> & /*current_f*/)
{
compute_log_strain_rate_deriv(current_u, pressure, temperature, diffusion_creep_parameters, dislocation_creep_parameters, log_strain_rate_deriv);
// Do nothing here, because we calculate the Jacobian in the residual function
};

nonlinear_solver.solve_with_jacobian = [&](const Vector<double> &rhs,
nonlinear_solver.solve_with_jacobian = [&](const Vector<double> &residual,
Vector<double> &solution,
const double /*tolerance*/)
{
solution(0) -= rhs(0)/log_strain_rate_deriv;
solution(0) = residual(0) / log_strain_rate_deriv;
};

nonlinear_solver.solve(log_stress_ii);
// Start with the assumption that all strain is accommodated by diffusion creep:
// If the diffusion creep prefactor is very small, that means that the diffusion viscosity is very large.
// In this case, use the maximum viscosity instead to compute the starting guess.
double stress_ii = (prefactor_stress_diffusion > (0.5 / maximum_viscosity)
?
edot_ii/prefactor_stress_diffusion
:
0.5 / maximum_viscosity);

// KINSOL works on vectors and so the scalar (log) stress is inserted into
// a vector of length 1
Vector<double> log_stress_ii(1);
log_stress_ii[0] = std::log(stress_ii);

nonlinear_solver.solve(log_stress_ii);
stress_ii = std::exp(log_stress_ii[0]);
composition_viscosities[j] = std::min(std::max(stress_ii/edot_ii/2, minimum_viscosity), maximum_viscosity);
}
return composition_viscosities;
}


template <int dim>
void
DiffusionDislocation<dim>::compute_log_strain_rate_deriv(
const Vector<double> &evaluation_point,
double pressure,
double temperature,
const Rheology::DiffusionCreepParameters diffusion_creep_parameters,
const Rheology::DislocationCreepParameters dislocation_creep_parameters,
double &log_strain_rate_deriv) const
{
const std::pair<double, double> log_diff_edot_and_deriv = diffusion_creep.compute_log_strain_rate_and_derivative(evaluation_point[0], pressure, temperature, diffusion_creep_parameters);
const std::pair<double, double> log_disl_edot_and_deriv = dislocation_creep.compute_log_strain_rate_and_derivative(evaluation_point[0], pressure, temperature, dislocation_creep_parameters);

const double strain_rate_diffusion = std::exp(log_diff_edot_and_deriv.first);
const double strain_rate_dislocation = std::exp(log_disl_edot_and_deriv.first);
log_strain_rate_deriv = (strain_rate_diffusion * log_diff_edot_and_deriv.second + strain_rate_dislocation * log_disl_edot_and_deriv.second)/
(strain_rate_diffusion + strain_rate_dislocation);
}



template <int dim>
void
DiffusionDislocation<dim>::compute_log_strain_rate_residual(
const Vector<double> &evaluation_point,
Vector<double> &residual,
double pressure,
double temperature,
std::pair<double, double>
DiffusionDislocation<dim>::compute_log_strain_rate_residual_and_derivative(
const double current_log_stress_ii,
const double pressure,
const double temperature,
const Rheology::DiffusionCreepParameters diffusion_creep_parameters,
const Rheology::DislocationCreepParameters dislocation_creep_parameters,
double log_edot_ii) const
const double log_edot_ii) const
{
const std::pair<double, double> log_diff_edot_and_deriv = diffusion_creep.compute_log_strain_rate_and_derivative(evaluation_point[0], pressure, temperature, diffusion_creep_parameters);
const std::pair<double, double> log_disl_edot_and_deriv = dislocation_creep.compute_log_strain_rate_and_derivative(evaluation_point[0], pressure, temperature, dislocation_creep_parameters);
const std::pair<double, double> log_diff_edot_and_deriv = diffusion_creep.compute_log_strain_rate_and_derivative(current_log_stress_ii, pressure, temperature, diffusion_creep_parameters);
const std::pair<double, double> log_disl_edot_and_deriv = dislocation_creep.compute_log_strain_rate_and_derivative(current_log_stress_ii, pressure, temperature, dislocation_creep_parameters);

const double strain_rate_diffusion = std::exp(log_diff_edot_and_deriv.first);
const double strain_rate_dislocation = std::exp(log_disl_edot_and_deriv.first);
double log_strain_rate_deriv = (strain_rate_diffusion * log_diff_edot_and_deriv.second + strain_rate_dislocation * log_disl_edot_and_deriv.second)/
(strain_rate_diffusion + strain_rate_dislocation);
const double log_strain_rate_iterate = std::log(strain_rate_diffusion + strain_rate_dislocation);
residual(0) = log_edot_ii - log_strain_rate_iterate;
return std::make_pair(log_strain_rate_iterate - log_edot_ii, log_strain_rate_deriv);
}

template <int dim>
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