/* poly/balance.c * * Copyright (C) 1996, 1997, 1998, 1999, 2000 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 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. */ static void balance_companion_matrix (double *m, size_t n); #define RADIX 2 #define RADIX2 (RADIX*RADIX) static void balance_companion_matrix (double *m, size_t nc) { int not_converged = 1; double row_norm = 0; double col_norm = 0; while (not_converged) { size_t i, j; double g, f, s; not_converged = 0; for (i = 0; i < nc; i++) { /* column norm, excluding the diagonal */ if (i != nc - 1) { col_norm = fabs (MAT (m, i + 1, i, nc)); } else { col_norm = 0; for (j = 0; j < nc - 1; j++) { col_norm += fabs (MAT (m, j, nc - 1, nc)); } } /* row norm, excluding the diagonal */ if (i == 0) { row_norm = fabs (MAT (m, 0, nc - 1, nc)); } else if (i == nc - 1) { row_norm = fabs (MAT (m, i, i - 1, nc)); } else { row_norm = (fabs (MAT (m, i, i - 1, nc)) + fabs (MAT (m, i, nc - 1, nc))); } if (col_norm == 0 || row_norm == 0) { continue; } g = row_norm / RADIX; f = 1; s = col_norm + row_norm; while (col_norm < g) { f *= RADIX; col_norm *= RADIX2; } g = row_norm * RADIX; while (col_norm > g) { f /= RADIX; col_norm /= RADIX2; } if ((row_norm + col_norm) < 0.95 * s * f) { not_converged = 1; g = 1 / f; if (i == 0) { MAT (m, 0, nc - 1, nc) *= g; } else { MAT (m, i, i - 1, nc) *= g; MAT (m, i, nc - 1, nc) *= g; } if (i == nc - 1) { for (j = 0; j < nc; j++) { MAT (m, j, i, nc) *= f; } } else { MAT (m, i + 1, i, nc) *= f; } } } } }

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