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/* blas/source_sbmv.h
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
*
* 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.
*/
{
INDEX i, j;
CHECK_ARGS12(SD_SBMV,order,Uplo,N,K,alpha,A,lda,X,incX,beta,Y,incY);
if (N == 0)
return;
if (alpha == 0.0 && beta == 1.0)
return;
/* form y := beta*y */
if (beta == 0.0) {
INDEX iy = OFFSET(N, incY);
for (i = 0; i < N; i++) {
Y[iy] = 0.0;
iy += incY;
}
} else if (beta != 1.0) {
INDEX iy = OFFSET(N, incY);
for (i = 0; i < N; i++) {
Y[iy] *= beta;
iy += incY;
}
}
if (alpha == 0.0)
return;
/* form y := alpha*A*x + y */
if ((order == CblasRowMajor && Uplo == CblasUpper)
|| (order == CblasColMajor && Uplo == CblasLower)) {
INDEX ix = OFFSET(N, incX);
INDEX iy = OFFSET(N, incY);
for (i = 0; i < N; i++) {
BASE tmp1 = alpha * X[ix];
BASE tmp2 = 0.0;
const INDEX j_min = i + 1;
const INDEX j_max = GSL_MIN(N, i + K + 1);
INDEX jx = OFFSET(N, incX) + j_min * incX;
INDEX jy = OFFSET(N, incY) + j_min * incY;
Y[iy] += tmp1 * A[0 + i * lda];
for (j = j_min; j < j_max; j++) {
BASE Aij = A[(j - i) + i * lda];
Y[jy] += tmp1 * Aij;
tmp2 += Aij * X[jx];
jx += incX;
jy += incY;
}
Y[iy] += alpha * tmp2;
ix += incX;
iy += incY;
}
} else if ((order == CblasRowMajor && Uplo == CblasLower)
|| (order == CblasColMajor && Uplo == CblasUpper)) {
INDEX ix = OFFSET(N, incX);
INDEX iy = OFFSET(N, incY);
for (i = 0; i < N; i++) {
BASE tmp1 = alpha * X[ix];
BASE tmp2 = 0.0;
const INDEX j_min = (i > K) ? i - K : 0;
const INDEX j_max = i;
INDEX jx = OFFSET(N, incX) + j_min * incX;
INDEX jy = OFFSET(N, incY) + j_min * incY;
for (j = j_min; j < j_max; j++) {
BASE Aij = A[(K - i + j) + i * lda];
Y[jy] += tmp1 * Aij;
tmp2 += Aij * X[jx];
jx += incX;
jy += incY;
}
Y[iy] += tmp1 * A[K + i * lda] + alpha * tmp2;
ix += incX;
iy += incY;
}
} else {
BLAS_ERROR("unrecognized operation");
}
}
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