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// Ceres Solver - A fast non-linear least squares minimizer
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// http://ceres-solver.org/
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// Author: markshachkov@gmail.com (Mark Shachkov)
#include "ceres/power_series_expansion_preconditioner.h"
#include "ceres/eigen_vector_ops.h"
#include "ceres/parallel_vector_ops.h"
namespace ceres::internal {
PowerSeriesExpansionPreconditioner::PowerSeriesExpansionPreconditioner(
const ImplicitSchurComplement* isc,
const int max_num_spse_iterations,
const double spse_tolerance,
const Preconditioner::Options& options)
: isc_(isc),
max_num_spse_iterations_(max_num_spse_iterations),
spse_tolerance_(spse_tolerance),
options_(options) {}
PowerSeriesExpansionPreconditioner::~PowerSeriesExpansionPreconditioner() =
default;
bool PowerSeriesExpansionPreconditioner::Update(const LinearOperator& /*A*/,
const double* /*D*/) {
return true;
}
void PowerSeriesExpansionPreconditioner::RightMultiplyAndAccumulate(
const double* x, double* y) const {
VectorRef yref(y, num_rows());
Vector series_term(num_rows());
Vector previous_series_term(num_rows());
ParallelSetZero(options_.context, options_.num_threads, yref);
isc_->block_diagonal_FtF_inverse()->RightMultiplyAndAccumulate(
x, y, options_.context, options_.num_threads);
ParallelAssign(
options_.context, options_.num_threads, previous_series_term, yref);
const double norm_threshold =
spse_tolerance_ * Norm(yref, options_.context, options_.num_threads);
for (int i = 1;; i++) {
ParallelSetZero(options_.context, options_.num_threads, series_term);
isc_->InversePowerSeriesOperatorRightMultiplyAccumulate(
previous_series_term.data(), series_term.data());
ParallelAssign(
options_.context, options_.num_threads, yref, yref + series_term);
if (i >= max_num_spse_iterations_ || series_term.norm() < norm_threshold) {
break;
}
std::swap(previous_series_term, series_term);
}
}
int PowerSeriesExpansionPreconditioner::num_rows() const {
return isc_->num_rows();
}
} // namespace ceres::internal