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muSpectre/src/solver/deprecated_solver_cg.cc
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deprecated_solver_cg.cc
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/**
* @file deprecated_solver_cg.cc
*
* @author Till Junge <till.junge@epfl.ch>
*
* @date 20 Dec 2017
*
* @brief Implementation of cg solver
*
* Copyright © 2017 Till Junge
*
* µSpectre is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser 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 Lesser General Public License
* along with µSpectre; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* * Boston, MA 02111-1307, USA.
*
* Additional permission under GNU GPL version 3 section 7
*
* If you modify this Program, or any covered work, by linking or combining it
* with proprietary FFT implementations or numerical libraries, containing parts
* covered by the terms of those libraries' licenses, the licensors of this
* Program grant you additional permission to convey the resulting work.
*/
#include "solver/deprecated_solver_cg.hh"
#include "solver/solver_common.hh"
#include <iomanip>
#include <cmath>
#include <sstream>
namespace muSpectre {
/* ---------------------------------------------------------------------- */
template <Dim_t DimS, Dim_t DimM>
DeprecatedSolverCG<DimS, DimM>::DeprecatedSolverCG(Cell_t & cell, Real tol,
Uint maxiter, bool verbose)
: Parent(cell, tol, maxiter, verbose), r_k{make_field<Field_t>(
"residual r_k",
this->collection)},
p_k{make_field<Field_t>("search direction r_k", this->collection)},
Ap_k{make_field<Field_t>("Effect of tangent A*p_k", this->collection)} {
}
/* ---------------------------------------------------------------------- */
template <Dim_t DimS, Dim_t DimM>
void DeprecatedSolverCG<DimS, DimM>::solve(const Field_t & rhs,
Field_t & x_f) {
x_f.eigenvec() = this->solve(rhs.eigenvec(), x_f.eigenvec());
}
//----------------------------------------------------------------------------//
template <Dim_t DimS, Dim_t DimM>
typename DeprecatedSolverCG<DimS, DimM>::SolvVectorOut
DeprecatedSolverCG<DimS, DimM>::solve(const SolvVectorInC rhs,
SolvVectorIn x_0) {
const Communicator & comm = this->cell.get_communicator();
// Following implementation of algorithm 5.2 in Nocedal's Numerical
// Optimization (p. 112)
auto r = this->r_k.eigen();
auto p = this->p_k.eigen();
auto Ap = this->Ap_k.eigen();
typename Field_t::EigenMap_t x(x_0.data(), r.rows(), r.cols());
// initialisation of algo
r = this->cell.directional_stiffness_with_copy(x);
r -= typename Field_t::ConstEigenMap_t(rhs.data(), r.rows(), r.cols());
p = -r;
this->converged = false;
Real rdr = comm.sum((r * r).sum());
Real rhs_norm2 = comm.sum(rhs.squaredNorm());
Real tol2 = ipow(this->tol, 2) * rhs_norm2;
size_t count_width{}; // for output formatting in verbose case
if (this->verbose) {
count_width = size_t(std::log10(this->maxiter)) + 1;
}
for (Uint i = 0; i < this->maxiter && (rdr > tol2 || i == 0);
++i, ++this->counter) {
Ap = this->cell.directional_stiffness_with_copy(p);
Real alpha = rdr / comm.sum((p * Ap).sum());
x += alpha * p;
r += alpha * Ap;
Real new_rdr = comm.sum((r * r).sum());
Real beta = new_rdr / rdr;
rdr = new_rdr;
if (this->verbose && comm.rank() == 0) {
std::cout << " at CG step " << std::setw(count_width) << i
<< ": |r|/|b| = " << std::setw(15)
<< std::sqrt(rdr / rhs_norm2) << ", cg_tol = " << this->tol
<< std::endl;
}
p = -r + beta * p;
}
if (rdr < tol2) {
this->converged = true;
} else {
std::stringstream err{};
err << " After " << this->counter << " steps, the solver "
<< " FAILED with |r|/|b| = " << std::setw(15)
<< std::sqrt(rdr / rhs_norm2) << ", cg_tol = " << this->tol
<< std::endl;
throw ConvergenceError("Conjugate gradient has not converged." +
err.str());
}
return x_0;
}
/* ---------------------------------------------------------------------- */
template <Dim_t DimS, Dim_t DimM>
typename DeprecatedSolverCG<DimS, DimM>::Tg_req_t
DeprecatedSolverCG<DimS, DimM>::get_tangent_req() const {
return tangent_requirement;
}
template class DeprecatedSolverCG<twoD, twoD>;
// template class DeprecatedSolverCG<twoD, threeD>;
template class DeprecatedSolverCG<threeD, threeD>;
} // namespace muSpectre
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