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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_PARAMETER_BLOCK_ORDERING_H_
+#define CERES_INTERNAL_PARAMETER_BLOCK_ORDERING_H_
+
+#include <vector>
+#include "ceres/ordered_groups.h"
+#include "ceres/graph.h"
+#include "ceres/types.h"
+
+namespace ceres {
+namespace internal {
+
+class Program;
+class ParameterBlock;
+
+// Uses an approximate independent set ordering to order the parameter
+// blocks of a problem so that it is suitable for use with Schur
+// complement based solvers. The output variable ordering contains an
+// ordering of the parameter blocks and the return value is size of
+// the independent set or the number of e_blocks (see
+// schur_complement_solver.h for an explanation). Constant parameters
+// are added to the end.
+//
+// The ordering vector has the structure
+//
+// ordering = [independent set,
+// complement of the independent set,
+// fixed blocks]
+int ComputeSchurOrdering(const Program& program,
+ std::vector<ParameterBlock* >* ordering);
+
+// Same as above, except that ties while computing the independent set
+// ordering are resolved in favour of the order in which the parameter
+// blocks occur in the program.
+int ComputeStableSchurOrdering(const Program& program,
+ std::vector<ParameterBlock* >* ordering);
+
+// Use an approximate independent set ordering to decompose the
+// parameter blocks of a problem in a sequence of independent
+// sets. The ordering covers all the non-constant parameter blocks in
+// the program.
+void ComputeRecursiveIndependentSetOrdering(const Program& program,
+ ParameterBlockOrdering* ordering);
+
+// Builds a graph on the parameter blocks of a Problem, whose
+// structure reflects the sparsity structure of the Hessian. Each
+// vertex corresponds to a parameter block in the Problem except for
+// parameter blocks that are marked constant. An edge connects two
+// parameter blocks, if they co-occur in a residual block.
+Graph<ParameterBlock*>* CreateHessianGraph(const Program& program);
+
+// Iterate over each of the groups in order of their priority and fill
+// summary with their sizes.
+void OrderingToGroupSizes(const ParameterBlockOrdering* ordering,
+ std::vector<int>* group_sizes);
+
+} // namespace internal
+} // namespace ceres
+
+#endif // CERES_INTERNAL_PARAMETER_BLOCK_ORDERING_H_