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- /* blas/source_rotmg.h
- *
- * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough
- *
- * 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.
- */
- {
- const BASE G = 4096.0, G2 = G * G;
- BASE D1 = *d1, D2 = *d2, x = *b1, y = b2;
- BASE h11, h12, h21, h22, u;
- BASE c, s;
- /* case of d1 < 0, appendix A, second to last paragraph */
- if (D1 < 0.0) {
- P[0] = -1;
- P[1] = 0;
- P[2] = 0;
- P[3] = 0;
- P[4] = 0;
- *d1 = 0;
- *d2 = 0;
- *b1 = 0;
- return;
- }
- if (D2 * y == 0.0) {
- P[0] = -2; /* case of H = I, page 315 */
- return;
- }
- c = fabs(D1 * x * x);
- s = fabs(D2 * y * y);
- if (c > s) {
- /* case of equation A6 */
- P[0] = 0.0;
- h11 = 1;
- h12 = (D2 * y) / (D1 * x);
- h21 = -y / x;
- h22 = 1;
- u = 1 - h21 * h12;
- if (u <= 0.0) { /* the case u <= 0 is rejected */
- P[0] = -1;
- P[1] = 0;
- P[2] = 0;
- P[3] = 0;
- P[4] = 0;
- *d1 = 0;
- *d2 = 0;
- *b1 = 0;
- return;
- }
- D1 /= u;
- D2 /= u;
- x *= u;
- } else {
- /* case of equation A7 */
- if (D2 * y * y < 0.0) {
- P[0] = -1;
- P[1] = 0;
- P[2] = 0;
- P[3] = 0;
- P[4] = 0;
- *d1 = 0;
- *d2 = 0;
- *b1 = 0;
- return;
- }
- P[0] = 1;
- h11 = (D1 * x) / (D2 * y);
- h12 = 1;
- h21 = -1;
- h22 = x / y;
- u = 1 + h11 * h22;
- D1 /= u;
- D2 /= u;
- {
- BASE tmp = D2;
- D2 = D1;
- D1 = tmp;
- }
- x = y * u;
- }
- /* rescale D1 to range [1/G2,G2] */
- while (D1 <= 1.0 / G2 && D1 != 0.0) {
- P[0] = -1;
- D1 *= G2;
- x /= G;
- h11 /= G;
- h12 /= G;
- }
- while (D1 >= G2) {
- P[0] = -1;
- D1 /= G2;
- x *= G;
- h11 *= G;
- h12 *= G;
- }
- /* rescale D2 to range [1/G2,G2] */
- while (fabs(D2) <= 1.0 / G2 && D2 != 0.0) {
- P[0] = -1;
- D2 *= G2;
- h21 /= G;
- h22 /= G;
- }
- while (fabs(D2) >= G2) {
- P[0] = -1;
- D2 /= G2;
- h21 *= G;
- h22 *= G;
- }
- *d1 = D1;
- *d2 = D2;
- *b1 = x;
- if (P[0] == -1.0) {
- P[1] = h11;
- P[2] = h21;
- P[3] = h12;
- P[4] = h22;
- } else if (P[0] == 0.0) {
- P[2] = h21;
- P[3] = h12;
- } else if (P[0] == 1.0) {
- P[1] = h11;
- P[4] = h22;
- }
- }
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