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/**
* @file gensvm_sparse.h
* @author G.J.J. van den Burg
* @date 2016-10-11
* @brief Header file for gensvm_sparse.c
*
* @details
* Contains declarations of the GenSparse structure and related functions.
*
* @copyright
Copyright 2016, G.J.J. van den Burg.
This file is part of GenSVM.
GenSVM is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
GenSVM is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GenSVM. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef GENSVM_SPARSE_H
#define GENSVM_SPARSE_H
// includes
#include "gensvm_globals.h"
// type declarations
/**
* @brief A structure to represent a sparse matrix in CSR format
*
* @details
* This structure holds a sparse matrix in the classic CSR format. Refer to
* <a href="https://en.wikipedia.org/wiki/Sparse_matrix">Wikipedia</a> for
* more details. The total storage requirement for this format is
* 2*nnz+n_row+1, so it only makes sense to use this format if the number of
* nonzeros is smaller than @f$(n_{row}(n_{col} - 1) - 1)/2@f$.
*
* @param nnz number of nonzero elements
* @param n_row rows of the matrix
* @param n_col columns of the matrix
* @param values nonzero values (length nnz)
* @param ia row indices (length n+1)
* @param ja column indices (length nnz)
*/
struct GenSparse {
long nnz;
///< number of nonzero elements
long n_row;
///< number of rows of the original matrix
long n_col;
///< number of columns of the original matrix
double *values;
///< actual nonzero values, should be of length nnz
long *ia;
///< cumulative row lengths, should be of length n_row+1
long *ja;
///< column indices, should be of length nnz
};
struct GenSparse *gensvm_init_sparse();
void gensvm_free_sparse(struct GenSparse *sp);
long gensvm_count_nnz(double *A, long rows, long cols);
bool gensvm_nnz_comparison(long nnz, long rows, long cols);
bool gensvm_could_sparse(double *A, long rows, long cols);
struct GenSparse *gensvm_dense_to_sparse(double *A, long rows, long cols);
double *gensvm_sparse_to_dense(struct GenSparse *A);
#endif
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