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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: sameeragarwal@google.com (Sameer Agarwal)
#include "ceres/schur_jacobi_preconditioner.h"
#include <memory>
#include <utility>
#include <vector>
#include "absl/log/check.h"
#include "ceres/block_random_access_diagonal_matrix.h"
#include "ceres/block_sparse_matrix.h"
#include "ceres/linear_solver.h"
#include "ceres/schur_eliminator.h"
namespace ceres::internal {
SchurJacobiPreconditioner::SchurJacobiPreconditioner(
const CompressedRowBlockStructure& bs, Preconditioner::Options options)
: options_(std::move(options)) {
CHECK_GT(options_.elimination_groups.size(), 1);
CHECK_GT(options_.elimination_groups[0], 0);
const int num_blocks = bs.cols.size() - options_.elimination_groups[0];
CHECK_GT(num_blocks, 0) << "Jacobian should have at least 1 f_block for "
<< "SCHUR_JACOBI preconditioner.";
CHECK(options_.context != nullptr);
std::vector<Block> blocks(num_blocks);
int position = 0;
for (int i = 0; i < num_blocks; ++i) {
blocks[i] =
Block(bs.cols[i + options_.elimination_groups[0]].size, position);
position += blocks[i].size;
}
m_ = std::make_unique<BlockRandomAccessDiagonalMatrix>(
blocks, options_.context, options_.num_threads);
InitEliminator(bs);
}
SchurJacobiPreconditioner::~SchurJacobiPreconditioner() = default;
// Initialize the SchurEliminator.
void SchurJacobiPreconditioner::InitEliminator(
const CompressedRowBlockStructure& bs) {
LinearSolver::Options eliminator_options;
eliminator_options.elimination_groups = options_.elimination_groups;
eliminator_options.num_threads = options_.num_threads;
eliminator_options.e_block_size = options_.e_block_size;
eliminator_options.f_block_size = options_.f_block_size;
eliminator_options.row_block_size = options_.row_block_size;
eliminator_options.context = options_.context;
eliminator_ = SchurEliminatorBase::Create(eliminator_options);
const bool kFullRankETE = true;
eliminator_->Init(
eliminator_options.elimination_groups[0], kFullRankETE, &bs);
}
// Update the values of the preconditioner matrix and factorize it.
bool SchurJacobiPreconditioner::UpdateImpl(const BlockSparseMatrix& A,
const double* D) {
const int num_rows = m_->num_rows();
CHECK_GT(num_rows, 0);
// Compute a subset of the entries of the Schur complement.
eliminator_->Eliminate(
BlockSparseMatrixData(A), nullptr, D, m_.get(), nullptr);
m_->Invert();
return true;
}
void SchurJacobiPreconditioner::RightMultiplyAndAccumulate(const double* x,
double* y) const {
m_->RightMultiplyAndAccumulate(x, y);
}
int SchurJacobiPreconditioner::num_rows() const { return m_->num_rows(); }
} // namespace ceres::internal