gensvm_sparse.c

Go to the documentation of this file.

#include "gensvm_sparse.h"

struct GenSparse *gensvm_init_sparse(void)
{
    struct GenSparse *sp = Malloc(struct GenSparse, 1);
    sp->nnz = 0;
    sp->n_row = 0;
    sp->n_col = 0;

    sp->values = NULL;
    sp->ia = NULL;
    sp->ja = NULL;

    return sp;
}

void gensvm_free_sparse(struct GenSparse *sp)
{
    free(sp->values);
    free(sp->ia);
    free(sp->ja);
    free(sp);
    sp = NULL;
}

long gensvm_count_nnz(double *A, long rows, long cols)
{
    long i, nnz = 0;

    for (i=0; i<rows*cols; i++)
        nnz += (A[i] != 0.0) ? 1 : 0;
    return nnz;
}

bool gensvm_nnz_comparison(long nnz, long rows, long cols)
{
    return (nnz < (rows*(cols-1.0)-1.0)/2.0);
}

bool gensvm_could_sparse(double *A, long rows, long cols)
{
    long nnz = gensvm_count_nnz(A, rows, cols);
    return gensvm_nnz_comparison(nnz, rows, cols);
}

struct GenSparse *gensvm_dense_to_sparse(double *A, long rows, long cols)
{
    double value;
    long row_cnt;
    long i, j, cnt, nnz = 0;
    struct GenSparse *spA = NULL;

    nnz = gensvm_count_nnz(A, rows, cols);

    spA = gensvm_init_sparse();

    spA->nnz = nnz;
    spA->n_row = rows;
    spA->n_col = cols;
    spA->values = Calloc(double, nnz);
    spA->ia = Calloc(long, rows+1);
    spA->ja = Calloc(long, nnz);

    cnt = 0;
    spA->ia[0] = 0;
    for (i=0; i<rows; i++) {
        row_cnt = 0;
        for (j=0; j<cols; j++) {
            value = matrix_get(A, cols, i, j);
            if (value != 0) {
                row_cnt++;
                spA->values[cnt] = value;
                spA->ja[cnt] = j;
                cnt++;
            }
        }
        spA->ia[i+1] = spA->ia[i] + row_cnt;
    }

    return spA;
}

double *gensvm_sparse_to_dense(struct GenSparse *A)
{
    double value;
    long i, j, jj;
    double *B = Calloc(double, (A->n_row)*(A->n_col));
    for (i=0; i<A->n_row; i++) {
        for (jj=A->ia[i]; jj<A->ia[i+1]; jj++) {
            j = A->ja[jj];
            value = A->values[jj];
            matrix_set(B, A->n_col, i, j, value);
        }
    }

    return B;
}