internal/ceres/cxsparse.h

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2012 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
//
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//   and/or other materials provided with the distribution.
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// Author: strandmark@google.com (Petter Strandmark)

#ifndef CERES_INTERNAL_CXSPARSE_H_
#define CERES_INTERNAL_CXSPARSE_H_

#ifndef CERES_NO_CXSPARSE

#include "cs.h"

namespace ceres {
namespace internal {

class CompressedRowSparseMatrix;
class TripletSparseMatrix;

// This object provides access to solving linear systems using Cholesky
// factorization with a known symbolic factorization. This features does not
// explicity exist in CXSparse. The methods in the class are nonstatic because
// the class manages internal scratch space.
class CXSparse {
 public:
  CXSparse();
  ~CXSparse();

  // Solves a symmetric linear system A * x = b using Cholesky factorization.
  //  A      - The system matrix.
  //  factor - The symbolic factorization of A. This is obtained from
  //           AnalyzeCholesky.
  //  b      - The right hand size of the linear equation. This array will also
  //           recieve the solution.
  // Returns false if Cholesky factorization of A fails.
  bool SolveCholesky(cs_di* A, cs_dis* factor, double* b);

  // Creates a sparse matrix from a compressed-column form. No memory is
  // allocated or copied; the structure A is filled out with info from the
  // argument.
  cs_di CreateSparseMatrixTransposeView(CompressedRowSparseMatrix* A);

  // Creates a new matrix from a triplet form. Deallocate the returned matrix
  // with Free. May return NULL if the compression or allocation fails.
  cs_di* CreateSparseMatrix(TripletSparseMatrix* A);

  // Computes a symbolic factorization of A that can be used in SolveCholesky.
  // The returned matrix should be deallocated with Free when not used anymore.
  cs_dis* AnalyzeCholesky(cs_di* A);

  // Deallocates the memory of a matrix obtained from AnalyzeCholesky.
  void Free(cs_di* factor);
  void Free(cs_dis* factor);

 private:
  // Cached scratch space
  CS_ENTRY* scratch_;
  int scratch_size_;
};

}  // namespace internal
}  // namespace ceres

#endif  // CERES_NO_CXSPARSE

#endif  // CERES_INTERNAL_CXSPARSE_H_