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/* spdgemv.c
*
* Copyright (C) 2012-2014 Patrick Alken
*
* This program 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.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <config.h>
#include <stdlib.h>
#include <math.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_vector.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_spmatrix.h>
#include <gsl/gsl_spblas.h>
#include <gsl/gsl_blas.h>
/*
gsl_spblas_dgemv()
Multiply a sparse matrix and a vector
Inputs: alpha - scalar factor
A - sparse matrix
x - dense vector
beta - scalar factor
y - (input/output) dense vector
Return: y = alpha*op(A)*x + beta*y
*/
int
gsl_spblas_dgemv(const CBLAS_TRANSPOSE_t TransA, const double alpha,
const gsl_spmatrix *A, const gsl_vector *x,
const double beta, gsl_vector *y)
{
const size_t M = A->size1;
const size_t N = A->size2;
if ((TransA == CblasNoTrans && N != x->size) ||
(TransA == CblasTrans && M != x->size))
{
GSL_ERROR("invalid length of x vector", GSL_EBADLEN);
}
else if ((TransA == CblasNoTrans && M != y->size) ||
(TransA == CblasTrans && N != y->size))
{
GSL_ERROR("invalid length of y vector", GSL_EBADLEN);
}
else
{
size_t j, p;
size_t incX, incY;
size_t lenX, lenY;
double *X, *Y;
double *Ad;
size_t *Ap, *Ai, *Aj;
if (TransA == CblasNoTrans)
{
lenX = N;
lenY = M;
}
else
{
lenX = M;
lenY = N;
}
/* form y := beta*y */
Y = y->data;
incY = y->stride;
if (beta == 0.0)
{
size_t jy = 0;
for (j = 0; j < lenY; ++j)
{
Y[jy] = 0.0;
jy += incY;
}
}
else if (beta != 1.0)
{
size_t jy = 0;
for (j = 0; j < lenY; ++j)
{
Y[jy] *= beta;
jy += incY;
}
}
if (alpha == 0.0)
return GSL_SUCCESS;
/* form y := alpha*op(A)*x + y */
Ap = A->p;
Ad = A->data;
X = x->data;
incX = x->stride;
if ((GSL_SPMATRIX_ISCCS(A) && (TransA == CblasNoTrans)) ||
(GSL_SPMATRIX_ISCRS(A) && (TransA == CblasTrans)))
{
Ai = A->i;
for (j = 0; j < lenX; ++j)
{
for (p = Ap[j]; p < Ap[j + 1]; ++p)
{
Y[Ai[p] * incY] += alpha * Ad[p] * X[j * incX];
}
}
}
else if ((GSL_SPMATRIX_ISCCS(A) && (TransA == CblasTrans)) ||
(GSL_SPMATRIX_ISCRS(A) && (TransA == CblasNoTrans)))
{
Ai = A->i;
for (j = 0; j < lenY; ++j)
{
for (p = Ap[j]; p < Ap[j + 1]; ++p)
{
Y[j * incY] += alpha * Ad[p] * X[Ai[p] * incX];
}
}
}
else if (GSL_SPMATRIX_ISTRIPLET(A))
{
if (TransA == CblasNoTrans)
{
Ai = A->i;
Aj = A->p;
}
else
{
Ai = A->p;
Aj = A->i;
}
for (p = 0; p < A->nz; ++p)
{
Y[Ai[p] * incY] += alpha * Ad[p] * X[Aj[p] * incX];
}
}
else
{
GSL_ERROR("unsupported matrix type", GSL_EINVAL);
}
return GSL_SUCCESS;
}
} /* gsl_spblas_dgemv() */
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