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/* blas/source_tbsv_r.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 2 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.
*/
{
const int nonunit = (Diag == CblasNonUnit);
INDEX i, j;
const int Trans = (TransA != CblasConjTrans) ? TransA : CblasTrans;
if (N == 0)
return;
/* form x := inv( A )*x */
if ((order == CblasRowMajor && Trans == CblasNoTrans && Uplo == CblasUpper)
|| (order == CblasColMajor && Trans == CblasTrans && Uplo == CblasLower)) {
/* backsubstitution */
INDEX ix = OFFSET(N, incX) + incX * (N - 1);
for (i = N; i > 0 && i--;) {
BASE tmp = X[ix];
const INDEX j_min = i + 1;
const INDEX j_max = GSL_MIN(N, i + K + 1);
INDEX jx = OFFSET(N, incX) + j_min * incX;
for (j = j_min; j < j_max; j++) {
const BASE Aij = A[lda * i + (j - i)];
tmp -= Aij * X[jx];
jx += incX;
}
if (nonunit) {
X[ix] = tmp / A[lda * i + 0];
} else {
X[ix] = tmp;
}
ix -= incX;
}
} else if ((order == CblasRowMajor && Trans == CblasNoTrans && Uplo == CblasLower)
|| (order == CblasColMajor && Trans == CblasTrans && Uplo == CblasUpper)) {
/* forward substitution */
INDEX ix = OFFSET(N, incX);
for (i = 0; i < N; i++) {
BASE tmp = X[ix];
const INDEX j_min = (i > K ? i - K : 0);
const INDEX j_max = i;
INDEX jx = OFFSET(N, incX) + j_min * incX;
for (j = j_min; j < j_max; j++) {
const BASE Aij = A[lda * i + (K + j - i)];
tmp -= Aij * X[jx];
jx += incX;
}
if (nonunit) {
X[ix] = tmp / A[lda * i + K];
} else {
X[ix] = tmp;
}
ix += incX;
}
} else if ((order == CblasRowMajor && Trans == CblasTrans && Uplo == CblasUpper)
|| (order == CblasColMajor && Trans == CblasNoTrans && Uplo == CblasLower)) {
/* form x := inv( A' )*x */
/* forward substitution */
INDEX ix = OFFSET(N, incX);
for (i = 0; i < N; i++) {
BASE tmp = X[ix];
const INDEX j_min = (K > i ? 0 : i - K);
const INDEX j_max = i;
INDEX jx = OFFSET(N, incX) + j_min * incX;
for (j = j_min; j < j_max; j++) {
const BASE Aji = A[(i - j) + lda * j];
tmp -= Aji * X[jx];
jx += incX;
}
if (nonunit) {
X[ix] = tmp / A[0 + lda * i];
} else {
X[ix] = tmp;
}
ix += incX;
}
} else if ((order == CblasRowMajor && Trans == CblasTrans && Uplo == CblasLower)
|| (order == CblasColMajor && Trans == CblasNoTrans && Uplo == CblasUpper)) {
/* backsubstitution */
INDEX ix = OFFSET(N, incX) + (N - 1) * incX;
for (i = N; i > 0 && i--;) {
BASE tmp = X[ix];
const INDEX j_min = i + 1;
const INDEX j_max = GSL_MIN(N, i + K + 1);
INDEX jx = OFFSET(N, incX) + j_min * incX;
for (j = j_min; j < j_max; j++) {
const BASE Aji = A[(K + i - j) + lda * j];
tmp -= Aji * X[jx];
jx += incX;
}
if (nonunit) {
X[ix] = tmp / A[K + lda * i];
} else {
X[ix] = tmp;
}
ix -= incX;
}
} else {
BLAS_ERROR("unrecognized operation");
}
}
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