internal/ceres/line_search_preprocessor.cc

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2023 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include "ceres/line_search_preprocessor.h"

#include <numeric>
#include <string>

#include "absl/log/check.h"
#include "ceres/casts.h"
#include "ceres/context_impl.h"
#include "ceres/evaluator.h"
#include "ceres/minimizer.h"
#include "ceres/problem_impl.h"
#include "ceres/program.h"

namespace ceres::internal {
namespace {

bool IsProgramValid(const Program& program, std::string* error) {
  if (program.IsBoundsConstrained()) {
    *error = "LINE_SEARCH Minimizer does not support bounds.";
    return false;
  }
  return program.ParameterBlocksAreFinite(error);
}

bool SetupEvaluator(PreprocessedProblem* pp) {
  pp->evaluator_options = Evaluator::Options();
  // This ensures that we get a Block Jacobian Evaluator without any
  // requirement on orderings.
  pp->evaluator_options.linear_solver_type = CGNR;
  pp->evaluator_options.num_eliminate_blocks = 0;
  pp->evaluator_options.num_threads = pp->options.num_threads;
  pp->evaluator_options.context = pp->problem->context();
  pp->evaluator_options.evaluation_callback =
      pp->reduced_program->mutable_evaluation_callback();
  pp->evaluator = Evaluator::Create(
      pp->evaluator_options, pp->reduced_program.get(), &pp->error);
  return (pp->evaluator.get() != nullptr);
}

}  // namespace

bool LineSearchPreprocessor::Preprocess(const Solver::Options& options,
                                        ProblemImpl* problem,
                                        PreprocessedProblem* pp) {
  CHECK(pp != nullptr);
  pp->options = options;
  ChangeNumThreadsIfNeeded(&pp->options);

  pp->problem = problem;
  Program* program = problem->mutable_program();
  if (!IsProgramValid(*program, &pp->error)) {
    return false;
  }

  pp->reduced_program = program->CreateReducedProgram(
      &pp->removed_parameter_blocks, &pp->fixed_cost, &pp->error);

  if (pp->reduced_program.get() == nullptr) {
    return false;
  }

  if (pp->reduced_program->NumParameterBlocks() == 0) {
    return true;
  }

  if (!SetupEvaluator(pp)) {
    return false;
  }

  SetupCommonMinimizerOptions(pp);
  return true;
}

}  // namespace ceres::internal