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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2015 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)
+
+#ifndef CERES_INTERNAL_COORDINATE_DESCENT_MINIMIZER_H_
+#define CERES_INTERNAL_COORDINATE_DESCENT_MINIMIZER_H_
+
+#include <string>
+#include <vector>
+
+#include "ceres/context_impl.h"
+#include "ceres/evaluator.h"
+#include "ceres/minimizer.h"
+#include "ceres/problem_impl.h"
+#include "ceres/solver.h"
+
+namespace ceres {
+namespace internal {
+
+class Program;
+class LinearSolver;
+
+// Given a Program, and a ParameterBlockOrdering which partitions
+// (non-exhaustively) the Hessian matrix into independent sets,
+// perform coordinate descent on the parameter blocks in the
+// ordering. The independent set structure allows for all parameter
+// blocks in the same independent set to be optimized in parallel, and
+// the order of the independent set determines the order in which the
+// parameter block groups are optimized.
+//
+// The minimizer assumes that none of the parameter blocks in the
+// program are constant.
+class CoordinateDescentMinimizer : public Minimizer {
+ public:
+ explicit CoordinateDescentMinimizer(ContextImpl* context);
+
+ bool Init(const Program& program,
+ const ProblemImpl::ParameterMap& parameter_map,
+ const ParameterBlockOrdering& ordering,
+ std::string* error);
+
+ // Minimizer interface.
+ virtual ~CoordinateDescentMinimizer();
+
+ virtual void Minimize(const Minimizer::Options& options,
+ double* parameters,
+ Solver::Summary* summary);
+
+ // Verify that each group in the ordering forms an independent set.
+ static bool IsOrderingValid(const Program& program,
+ const ParameterBlockOrdering& ordering,
+ std::string* message);
+
+ // 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.
+ static ParameterBlockOrdering* CreateOrdering(const Program& program);
+
+ private:
+ void Solve(Program* program,
+ LinearSolver* linear_solver,
+ double* parameters,
+ Solver::Summary* summary);
+
+ std::vector<ParameterBlock*> parameter_blocks_;
+ std::vector<std::vector<ResidualBlock*>> residual_blocks_;
+ // The optimization is performed in rounds. In each round all the
+ // parameter blocks that form one independent set are optimized in
+ // parallel. This array, marks the boundaries of the independent
+ // sets in parameter_blocks_.
+ std::vector<int> independent_set_offsets_;
+
+ Evaluator::Options evaluator_options_;
+
+ ContextImpl* context_;
+};
+
+} // namespace internal
+} // namespace ceres
+
+#endif // CERES_INTERNAL_COORDINATE_DESCENT_MINIMIZER_H_