internal/ceres/coordinate_descent_minimizer.cc - ceres-solver - Git at Google

 // Ceres Solver - A fast non-linear least squares minimizer
 // Copyright 2023 Google Inc. All rights reserved.
 // http://ceres-solver.org/
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //
 // * Redistributions of source code must retain the above copyright notice,
 //   this list of conditions and the following disclaimer.
 // * Redistributions in binary form must reproduce the above copyright notice,
 //   this list of conditions and the following disclaimer in the documentation
 //   and/or other materials provided with the distribution.
 // * Neither the name of Google Inc. nor the names of its contributors may be
 //   used to endorse or promote products derived from this software without
 //   specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 // POSSIBILITY OF SUCH DAMAGE.
 //
 // Author: sameeragarwal@google.com (Sameer Agarwal)

 #include "ceres/coordinate_descent_minimizer.h"

 #include <algorithm>
 #include <iterator>
 #include <map>
 #include <memory>
 #include <numeric>
 #include <set>
 #include <string>
 #include <vector>

 #include "absl/log/check.h"
 #include "absl/strings/str_format.h"
 #include "ceres/evaluator.h"
 #include "ceres/linear_solver.h"
 #include "ceres/minimizer.h"
 #include "ceres/parallel_for.h"
 #include "ceres/parameter_block.h"
 #include "ceres/parameter_block_ordering.h"
 #include "ceres/problem_impl.h"
 #include "ceres/program.h"
 #include "ceres/residual_block.h"
 #include "ceres/solver.h"
 #include "ceres/trust_region_minimizer.h"
 #include "ceres/trust_region_strategy.h"

 namespace ceres::internal {

 CoordinateDescentMinimizer::CoordinateDescentMinimizer(ContextImpl* context)
     : context_(context) {
   CHECK(context_ != nullptr);
 }

 CoordinateDescentMinimizer::~CoordinateDescentMinimizer() = default;

 bool CoordinateDescentMinimizer::Init(
     const Program& program,
     const ProblemImpl::ParameterMap& parameter_map,
     const ParameterBlockOrdering& ordering,
     std::string* /*error*/) {
   parameter_blocks_.clear();
   independent_set_offsets_.clear();
   independent_set_offsets_.push_back(0);

   // Serialize the OrderedGroups into a vector of parameter block
   // offsets for parallel access.

   // TODO(sameeragarwal): Investigate if parameter_block_index should be an
   // ordered or an unordered container.
   std::map<ParameterBlock*, int> parameter_block_index;
   std::map<int, std::set<double*>> group_to_elements =
       ordering.group_to_elements();
   for (const auto& g_t_e : group_to_elements) {
     const auto& elements = g_t_e.second;
     for (double* parameter_block : elements) {
       parameter_blocks_.push_back(parameter_map.find(parameter_block)->second);
       parameter_block_index[parameter_blocks_.back()] =
           parameter_blocks_.size() - 1;
     }
     independent_set_offsets_.push_back(independent_set_offsets_.back() +
                                        elements.size());
   }

   // The ordering does not have to contain all parameter blocks, so
   // assign zero offsets/empty independent sets to these parameter
   // blocks.
   const std::vector<ParameterBlock*>& parameter_blocks =
       program.parameter_blocks();
   for (auto* parameter_block : parameter_blocks) {
     if (!ordering.IsMember(parameter_block->mutable_user_state())) {
       parameter_blocks_.push_back(parameter_block);
       independent_set_offsets_.push_back(independent_set_offsets_.back());
     }
   }

   // Compute the set of residual blocks that depend on each parameter
   // block.
   residual_blocks_.resize(parameter_block_index.size());
   const std::vector<ResidualBlock*>& residual_blocks =
       program.residual_blocks();
   for (auto* residual_block : residual_blocks) {
     const int num_parameter_blocks = residual_block->NumParameterBlocks();
     for (int j = 0; j < num_parameter_blocks; ++j) {
       ParameterBlock* parameter_block = residual_block->parameter_blocks()[j];
       const auto it = parameter_block_index.find(parameter_block);
       if (it != parameter_block_index.end()) {
         residual_blocks_[it->second].push_back(residual_block);
       }
     }
   }

   evaluator_options_.linear_solver_type = DENSE_QR;
   evaluator_options_.num_eliminate_blocks = 0;
   evaluator_options_.num_threads = 1;
   evaluator_options_.context = context_;

   return true;
 }

 void CoordinateDescentMinimizer::Minimize(const Minimizer::Options& options,
                                           double* parameters,
                                           Solver::Summary* /*summary*/) {
   // Set the state and mark all parameter blocks constant.
   for (auto* parameter_block : parameter_blocks_) {
     parameter_block->SetState(parameters + parameter_block->state_offset());
     parameter_block->SetConstant();
   }

   std::vector<std::unique_ptr<LinearSolver>> linear_solvers(
       options.num_threads);

   LinearSolver::Options linear_solver_options;
   linear_solver_options.type = DENSE_QR;
   linear_solver_options.context = context_;

   for (int i = 0; i < options.num_threads; ++i) {
     linear_solvers[i] = LinearSolver::Create(linear_solver_options);
   }

   for (int i = 0; i < independent_set_offsets_.size() - 1; ++i) {
     const int num_problems =
         independent_set_offsets_[i + 1] - independent_set_offsets_[i];
     // Avoid parallelization overhead call if the set is empty.
     if (num_problems == 0) {
       continue;
     }

     const int num_inner_iteration_threads =
         std::min(options.num_threads, num_problems);
     evaluator_options_.num_threads =
         std::max(1, options.num_threads / num_inner_iteration_threads);

     // The parameter blocks in each independent set can be optimized
     // in parallel, since they do not co-occur in any residual block.
     ParallelFor(
         context_,
         independent_set_offsets_[i],
         independent_set_offsets_[i + 1],
         num_inner_iteration_threads,
         [&](int thread_id, int j) {
           ParameterBlock* parameter_block = parameter_blocks_[j];
           const int old_index = parameter_block->index();
           const int old_delta_offset = parameter_block->delta_offset();
           const int old_state_offset = parameter_block->state_offset();
           parameter_block->SetVarying();
           parameter_block->set_index(0);
           parameter_block->set_delta_offset(0);
           parameter_block->set_state_offset(0);

           Program inner_program;
           inner_program.mutable_parameter_blocks()->push_back(parameter_block);
           *inner_program.mutable_residual_blocks() = residual_blocks_[j];

           // TODO(sameeragarwal): Better error handling. Right now we
           // assume that this is not going to lead to problems of any
           // sort. Basically we should be checking for numerical failure
           // of some sort.
           //
           // On the other hand, if the optimization is a failure, that in
           // some ways is fine, since it won't change the parameters and
           // we are fine.
           Solver::Summary inner_summary;
           Solve(&inner_program,
                 linear_solvers[thread_id].get(),
                 parameters + old_state_offset,
                 &inner_summary);

           parameter_block->set_index(old_index);
           parameter_block->set_delta_offset(old_delta_offset);
           parameter_block->set_state_offset(old_state_offset);
           parameter_block->SetState(parameters +
                                     parameter_block->state_offset());
           parameter_block->SetConstant();
         });
   }

   for (auto* parameter_block : parameter_blocks_) {
     parameter_block->SetVarying();
   }
 }

 // Solve the optimization problem for one parameter block.
 void CoordinateDescentMinimizer::Solve(Program* program,
                                        LinearSolver* linear_solver,
                                        double* parameter,
                                        Solver::Summary* summary) {
   *summary = Solver::Summary();
   summary->initial_cost = 0.0;
   summary->fixed_cost = 0.0;
   summary->final_cost = 0.0;
   std::string error;

   Minimizer::Options minimizer_options;
   minimizer_options.evaluator =
       Evaluator::Create(evaluator_options_, program, &error);
   CHECK(minimizer_options.evaluator != nullptr);
   minimizer_options.jacobian = minimizer_options.evaluator->CreateJacobian();
   CHECK(minimizer_options.jacobian != nullptr);

   TrustRegionStrategy::Options trs_options;
   trs_options.linear_solver = linear_solver;
   minimizer_options.trust_region_strategy =
       TrustRegionStrategy::Create(trs_options);
   CHECK(minimizer_options.trust_region_strategy != nullptr);
   minimizer_options.is_silent = true;

   TrustRegionMinimizer minimizer;
   minimizer.Minimize(minimizer_options, parameter, summary);
 }

 bool CoordinateDescentMinimizer::IsOrderingValid(
     const Program& program,
     const ParameterBlockOrdering& ordering,
     std::string* message) {
   // TODO(sameeragarwal): Investigate if this should be an ordered or an
   // unordered group.
   const std::map<int, std::set<double*>>& group_to_elements =
       ordering.group_to_elements();

   // Verify that each group is an independent set
   for (const auto& g_t_e : group_to_elements) {
     if (!program.IsParameterBlockSetIndependent(g_t_e.second)) {
       *message = absl::StrFormat(
           "The user-provided parameter_blocks_for_inner_iterations does not "
           "form an independent set. Group Id: %d",
           g_t_e.first);
       return false;
     }
   }
   return true;
 }

 // Find a recursive decomposition of the Hessian matrix as a set
 // of independent sets of decreasing size and invert it. This
 // seems to work better in practice, i.e., Cameras before
 // points.
 std::shared_ptr<ParameterBlockOrdering>
 CoordinateDescentMinimizer::CreateOrdering(const Program& program) {
   auto ordering = std::make_shared<ParameterBlockOrdering>();
   ComputeRecursiveIndependentSetOrdering(program, ordering.get());
   ordering->Reverse();
   return ordering;
 }

 }  // namespace ceres::internal
	// Ceres Solver - A fast non-linear least squares minimizer
	// Copyright 2023 Google Inc. All rights reserved.
	// http://ceres-solver.org/
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// * Redistributions of source code must retain the above copyright notice,
	// this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	// * Neither the name of Google Inc. nor the names of its contributors may be
	// used to endorse or promote products derived from this software without
	// specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
	// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
	// POSSIBILITY OF SUCH DAMAGE.
	//
	// Author: sameeragarwal@google.com (Sameer Agarwal)

	#include "ceres/coordinate_descent_minimizer.h"

	#include <algorithm>
	#include <iterator>
	#include <map>
	#include <memory>
	#include <numeric>
	#include <set>
	#include <string>
	#include <vector>

	#include "absl/log/check.h"
	#include "absl/strings/str_format.h"
	#include "ceres/evaluator.h"
	#include "ceres/linear_solver.h"
	#include "ceres/minimizer.h"
	#include "ceres/parallel_for.h"
	#include "ceres/parameter_block.h"
	#include "ceres/parameter_block_ordering.h"
	#include "ceres/problem_impl.h"
	#include "ceres/program.h"
	#include "ceres/residual_block.h"
	#include "ceres/solver.h"
	#include "ceres/trust_region_minimizer.h"
	#include "ceres/trust_region_strategy.h"

	namespace ceres::internal {

	CoordinateDescentMinimizer::CoordinateDescentMinimizer(ContextImpl* context)
	: context_(context) {
	CHECK(context_ != nullptr);
	}

	CoordinateDescentMinimizer::~CoordinateDescentMinimizer() = default;

	bool CoordinateDescentMinimizer::Init(
	const Program& program,
	const ProblemImpl::ParameterMap& parameter_map,
	const ParameterBlockOrdering& ordering,
	std::string* /error/) {
	parameter_blocks_.clear();
	independent_set_offsets_.clear();
	independent_set_offsets_.push_back(0);

	// Serialize the OrderedGroups into a vector of parameter block
	// offsets for parallel access.

	// TODO(sameeragarwal): Investigate if parameter_block_index should be an
	// ordered or an unordered container.
	std::map<ParameterBlock*, int> parameter_block_index;
	std::map<int, std::set<double*>> group_to_elements =
	ordering.group_to_elements();
	for (const auto& g_t_e : group_to_elements) {
	const auto& elements = g_t_e.second;
	for (double* parameter_block : elements) {
	parameter_blocks_.push_back(parameter_map.find(parameter_block)->second);
	parameter_block_index[parameter_blocks_.back()] =
	parameter_blocks_.size() - 1;
	}
	independent_set_offsets_.push_back(independent_set_offsets_.back() +
	elements.size());
	}

	// The ordering does not have to contain all parameter blocks, so
	// assign zero offsets/empty independent sets to these parameter
	// blocks.
	const std::vector<ParameterBlock*>& parameter_blocks =
	program.parameter_blocks();
	for (auto* parameter_block : parameter_blocks) {
	if (!ordering.IsMember(parameter_block->mutable_user_state())) {
	parameter_blocks_.push_back(parameter_block);
	independent_set_offsets_.push_back(independent_set_offsets_.back());
	}
	}

	// Compute the set of residual blocks that depend on each parameter
	// block.
	residual_blocks_.resize(parameter_block_index.size());
	const std::vector<ResidualBlock*>& residual_blocks =
	program.residual_blocks();
	for (auto* residual_block : residual_blocks) {
	const int num_parameter_blocks = residual_block->NumParameterBlocks();
	for (int j = 0; j < num_parameter_blocks; ++j) {
	ParameterBlock* parameter_block = residual_block->parameter_blocks()[j];
	const auto it = parameter_block_index.find(parameter_block);
	if (it != parameter_block_index.end()) {
	residual_blocks_[it->second].push_back(residual_block);
	}
	}
	}

	evaluator_options_.linear_solver_type = DENSE_QR;
	evaluator_options_.num_eliminate_blocks = 0;
	evaluator_options_.num_threads = 1;
	evaluator_options_.context = context_;

	return true;
	}

	void CoordinateDescentMinimizer::Minimize(const Minimizer::Options& options,
	double* parameters,
	Solver::Summary* /summary/) {
	// Set the state and mark all parameter blocks constant.
	for (auto* parameter_block : parameter_blocks_) {
	parameter_block->SetState(parameters + parameter_block->state_offset());
	parameter_block->SetConstant();
	}

	std::vector<std::unique_ptr<LinearSolver>> linear_solvers(
	options.num_threads);

	LinearSolver::Options linear_solver_options;
	linear_solver_options.type = DENSE_QR;
	linear_solver_options.context = context_;

	for (int i = 0; i < options.num_threads; ++i) {
	linear_solvers[i] = LinearSolver::Create(linear_solver_options);
	}

	for (int i = 0; i < independent_set_offsets_.size() - 1; ++i) {
	const int num_problems =
	independent_set_offsets_[i + 1] - independent_set_offsets_[i];
	// Avoid parallelization overhead call if the set is empty.
	if (num_problems == 0) {
	continue;
	}

	const int num_inner_iteration_threads =
	std::min(options.num_threads, num_problems);
	evaluator_options_.num_threads =
	std::max(1, options.num_threads / num_inner_iteration_threads);

	// The parameter blocks in each independent set can be optimized
	// in parallel, since they do not co-occur in any residual block.
	ParallelFor(
	context_,
	independent_set_offsets_[i],
	independent_set_offsets_[i + 1],
	num_inner_iteration_threads,
	[&](int thread_id, int j) {
	ParameterBlock* parameter_block = parameter_blocks_[j];
	const int old_index = parameter_block->index();
	const int old_delta_offset = parameter_block->delta_offset();
	const int old_state_offset = parameter_block->state_offset();
	parameter_block->SetVarying();
	parameter_block->set_index(0);
	parameter_block->set_delta_offset(0);
	parameter_block->set_state_offset(0);

	Program inner_program;
	inner_program.mutable_parameter_blocks()->push_back(parameter_block);
	*inner_program.mutable_residual_blocks() = residual_blocks_[j];

	// TODO(sameeragarwal): Better error handling. Right now we
	// assume that this is not going to lead to problems of any
	// sort. Basically we should be checking for numerical failure
	// of some sort.
	//
	// On the other hand, if the optimization is a failure, that in
	// some ways is fine, since it won't change the parameters and
	// we are fine.
	Solver::Summary inner_summary;
	Solve(&inner_program,
	linear_solvers[thread_id].get(),
	parameters + old_state_offset,
	&inner_summary);

	parameter_block->set_index(old_index);
	parameter_block->set_delta_offset(old_delta_offset);
	parameter_block->set_state_offset(old_state_offset);
	parameter_block->SetState(parameters +
	parameter_block->state_offset());
	parameter_block->SetConstant();
	});
	}

	for (auto* parameter_block : parameter_blocks_) {
	parameter_block->SetVarying();
	}
	}

	// Solve the optimization problem for one parameter block.
	void CoordinateDescentMinimizer::Solve(Program* program,
	LinearSolver* linear_solver,
	double* parameter,
	Solver::Summary* summary) {
	*summary = Solver::Summary();
	summary->initial_cost = 0.0;
	summary->fixed_cost = 0.0;
	summary->final_cost = 0.0;
	std::string error;

	Minimizer::Options minimizer_options;
	minimizer_options.evaluator =
	Evaluator::Create(evaluator_options_, program, &error);
	CHECK(minimizer_options.evaluator != nullptr);
	minimizer_options.jacobian = minimizer_options.evaluator->CreateJacobian();
	CHECK(minimizer_options.jacobian != nullptr);

	TrustRegionStrategy::Options trs_options;
	trs_options.linear_solver = linear_solver;
	minimizer_options.trust_region_strategy =
	TrustRegionStrategy::Create(trs_options);
	CHECK(minimizer_options.trust_region_strategy != nullptr);
	minimizer_options.is_silent = true;

	TrustRegionMinimizer minimizer;
	minimizer.Minimize(minimizer_options, parameter, summary);
	}

	bool CoordinateDescentMinimizer::IsOrderingValid(
	const Program& program,
	const ParameterBlockOrdering& ordering,
	std::string* message) {
	// TODO(sameeragarwal): Investigate if this should be an ordered or an
	// unordered group.
	const std::map<int, std::set<double*>>& group_to_elements =
	ordering.group_to_elements();

	// Verify that each group is an independent set
	for (const auto& g_t_e : group_to_elements) {
	if (!program.IsParameterBlockSetIndependent(g_t_e.second)) {
	*message = absl::StrFormat(
	"The user-provided parameter_blocks_for_inner_iterations does not "
	"form an independent set. Group Id: %d",
	g_t_e.first);
	return false;
	}
	}
	return true;
	}

	// Find a recursive decomposition of the Hessian matrix as a set
	// of independent sets of decreasing size and invert it. This
	// seems to work better in practice, i.e., Cameras before
	// points.
	std::shared_ptr<ParameterBlockOrdering>
	CoordinateDescentMinimizer::CreateOrdering(const Program& program) {
	auto ordering = std::make_shared<ParameterBlockOrdering>();
	ComputeRecursiveIndependentSetOrdering(program, ordering.get());
	ordering->Reverse();
	return ordering;
	}

	} // namespace ceres::internal