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new_solvers.cc
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/**
* file new_solvers.cc
*
* @author Till Junge <till.junge@epfl.ch>
*
* @date 24 Apr 2018
*
* @brief implementation of dynamic newton-cg solver
*
* @section LICENSE
*
* Copyright © 2018 Till Junge
*
* µSpectre is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, either version 3, or (at
* your option) any later version.
*
* µSpectre is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Emacs; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include "new_solvers.hh"
#include <Eigen/Dense>
#include <iomanip>
namespace muSpectre {
std::vector<OptimizeResult>
newton_cg_dyn(Cell & cell, const std::vector<Eigen::MatrixXd> load_steps,
SolverBaseDyn & solver, Real newton_tol,
Real equil_tol, Dim_t verbose) {
const Communicator & comm = cell.get_communicator();
using Vector_t = Eigen::Matrix<Real, Eigen::Dynamic, 1>;
using Matrix_t = Eigen::Matrix<Real, Eigen::Dynamic, Eigen::Dynamic>;
// Corresponds to symbol δF or δε
Vector_t incrF(cell.get_nb_dof());
Vector_t rhs(cell.get_nb_dof());
solver.initialise();
size_t count_width{};
const auto form{cell.get_formulation()};
std::string strain_symb{};
if (verbose > 0 && comm.rank() == 0) {
//setup of algorithm 5.2 in Nocedal, Numerical Optimization (p. 111)
std::cout << "Newton-" << solver.get_name() << " for ";
switch (form) {
case Formulation::small_strain: {
strain_symb = "ε";
std::cout << "small";
break;
}
case Formulation::finite_strain: {
strain_symb = "F";
std::cout << "finite";
break;
}
default:
throw SolverError("unknown formulation");
break;
}
std::cout << " strain with" << std::endl
<< "newton_tol = " << newton_tol << ", cg_tol = "
<< solver.get_tol() << " maxiter = " << solver.get_maxiter() << " and Δ"
<< strain_symb << " =" <<std::endl;
for (auto&& tup: akantu::enumerate(load_steps)) {
auto && counter{std::get<0>(tup)};
auto && grad{std::get<1>(tup)};
std::cout << "Step " << counter + 1 << ":" << std::endl
<< grad << std::endl;
}
count_width = size_t(std::log10(solver.get_maxiter()))+1;
}
const Dim_t mat_dim{cell.get_material_dim()};
auto shape{cell.get_strain_shape()};
switch (form) {
case Formulation::finite_strain: {
cell.set_uniform_strain(Matrix_t::Identity(mat_dim, mat_dim));
for (const auto & delF: load_steps) {
if (not (delF.cols() == mat_dim) and not (delF.rows() == mat_dim)) {
std::stringstream err{};
err << "Load increments need to be given in " << mat_dim << "×"
<< mat_dim << " matrices, but I got a " << delF.rows() << "×"
<< delF.cols() << " matrix.";
throw SolverError(err.str());
}
}
break;
}
case Formulation::small_strain: {
cell.set_uniform_strain(Matrix_t::Zero(mat_dim, mat_dim));
for (const auto & delF: load_steps) {
if (not (delF.cols() == mat_dim) and not (delF.rows() == mat_dim)) {
std::stringstream err{};
err << "Load increments need to be given in " << mat_dim << "×"
<< mat_dim << " matrices, but I got a " << delF.rows() << "×"
<< delF.cols() << " matrix.";
throw SolverError(err.str());
}
if (not check_symmetry(delF)) {
throw SolverError("all Δε must be symmetric!");
}
}
break;
}
default:
throw SolverError("Unknown strain measure");
break;
}
// initialise return value
std::vector<OptimizeResult> ret_val{};
// storage for the previous mean strain (to compute ΔF or Δε)
Matrix_t previous_macro_strain{load_steps.back().Zero(shape[0], shape[1])};
auto F{cell.get_strain_vector()};
//! incremental loop
for (const auto & macro_strain: load_steps) {
using StrainMap_t = RawFieldMap<Eigen::Map<Eigen::MatrixXd>>;
for (auto && strain: StrainMap_t(F, shape[0], shape[1])) {
strain += macro_strain - previous_macro_strain;
}
std::string message{"Has not converged"};
Real incr_norm{2*newton_tol}, grad_norm{1};
Real stress_norm{2*equil_tol};
bool has_converged{false};
auto convergence_test = [&incr_norm, &grad_norm, &newton_tol,
&stress_norm, &equil_tol, &message, &has_converged] () {
bool incr_test = incr_norm/grad_norm <= newton_tol;
bool stress_test = stress_norm < equil_tol;
if (incr_test) {
message = "Residual tolerance reached";
} else if (stress_test) {
message = "Reached stress divergence tolerance";
}
has_converged = incr_test || stress_test;
return has_converged;
};
Uint newt_iter{0};
for (;
newt_iter < solver.get_maxiter() && !has_converged;
++newt_iter) {
// obtain material response
auto res_tup{cell.evaluate_stress_tangent()};
auto & P{std::get<0>(res_tup)};
rhs = -P;
cell.apply_projection(rhs);
stress_norm = std::sqrt(comm.sum(rhs.squaredNorm()));
if (convergence_test()) {
break;
}
//! this is a potentially avoidable copy TODO: check this out
incrF = solver.solve(rhs);
F += incrF;
incr_norm = std::sqrt(comm.sum(incrF.squaredNorm()));
grad_norm = std::sqrt(comm.sum(F.squaredNorm()));
if ((verbose > 0) and (comm.rank() == 0)) {
std::cout << "at Newton step " << std::setw(count_width) << newt_iter
<< ", |δ" << strain_symb << "|/|Δ" << strain_symb
<< "| = " << std::setw(17) << incr_norm/grad_norm
<< ", tol = " << newton_tol << std::endl;
if (verbose-1>1) {
std::cout << "<" << strain_symb << "> =" << std::endl
<< StrainMap_t(F, shape[0], shape[1]).mean() << std::endl;
}
}
convergence_test();
}
// update previous macroscopic strain
previous_macro_strain = macro_strain;
// store results
ret_val.emplace_back(OptimizeResult{F, cell.get_stress_vector(),
convergence_test(), Int(convergence_test()),
message, newt_iter, solver.get_counter()});
// store history variables for next load increment
cell.save_history_variables();
}
return ret_val;
}
} // muSpectre

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