// 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)

#ifndef CERES_INTERNAL_DETECT_STRUCTURE_H_
#define CERES_INTERNAL_DETECT_STRUCTURE_H_

#include "ceres/block_structure.h"
#include "ceres/internal/disable_warnings.h"
#include "ceres/internal/export.h"

namespace ceres::internal {

// Detect static blocks in the problem sparsity. For rows containing
// e_blocks, we are interested in detecting if the size of the row
// blocks, e_blocks and the f_blocks remain constant. If they do, then
// we can use template specialization to improve the performance of
// the block level linear algebra operations used by the
// SchurEliminator.
//
// If a block size is not constant, we return Eigen::Dynamic as the
// value. This just means that the eliminator uses dynamically sized
// linear algebra operations rather than static operations whose size
// is known as compile time.
//
// For more details about e_blocks and f_blocks, see
// schur_eliminator.h. This information is used to initialized an
// appropriate template specialization of SchurEliminator.
//
// Note: The structure of rows without any e-blocks has no effect on
// the values returned by this function. It is entirely possible that
// the f_block_size and row_blocks_size is not constant in such rows.
void CERES_NO_EXPORT DetectStructure(const CompressedRowBlockStructure& bs,
                                     const int num_eliminate_blocks,
                                     int* row_block_size,
                                     int* e_block_size,
                                     int* f_block_size);

}  // namespace ceres::internal

#include "ceres/internal/reenable_warnings.h"

#endif  // CERES_INTERNAL_DETECT_STRUCTURE_H_
