123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104 |
- /* poly/zsolve_quadratic.c
- *
- * 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.
- */
- /* complex_solve_quadratic.c - finds complex roots of a x^2 + b x + c = 0 */
- #include "gsl__config.h"
- #include <math.h>
- #include "gsl_complex.h"
- #include "gsl_poly.h"
- int
- gsl_poly_complex_solve_quadratic (double a, double b, double c,
- gsl_complex *z0, gsl_complex *z1)
- {
- double disc = b * b - 4 * a * c;
- if (a == 0) /* Handle linear case */
- {
- if (b == 0)
- {
- return 0;
- }
- else
- {
- GSL_REAL(*z0) = -c / b;
- GSL_IMAG(*z0) = 0;
- return 1;
- };
- }
- if (disc > 0)
- {
- if (b == 0)
- {
- double s = fabs (0.5 * sqrt (disc) / a);
- GSL_REAL (*z0) = -s;
- GSL_IMAG (*z0) = 0;
- GSL_REAL (*z1) = s;
- GSL_IMAG (*z1) = 0;
- }
- else
- {
- double sgnb = (b > 0 ? 1 : -1);
- double temp = -0.5 * (b + sgnb * sqrt (disc));
- double r1 = temp / a;
- double r2 = c / temp;
- if (r1 < r2)
- {
- GSL_REAL (*z0) = r1;
- GSL_IMAG (*z0) = 0;
- GSL_REAL (*z1) = r2;
- GSL_IMAG (*z1) = 0;
- }
- else
- {
- GSL_REAL (*z0) = r2;
- GSL_IMAG (*z0) = 0;
- GSL_REAL (*z1) = r1;
- GSL_IMAG (*z1) = 0;
- }
- }
- return 2;
- }
- else if (disc == 0)
- {
- GSL_REAL (*z0) = -0.5 * b / a;
- GSL_IMAG (*z0) = 0;
- GSL_REAL (*z1) = -0.5 * b / a;
- GSL_IMAG (*z1) = 0;
- return 2;
- }
- else
- {
- double s = fabs (0.5 * sqrt (-disc) / a);
- GSL_REAL (*z0) = -0.5 * b / a;
- GSL_IMAG (*z0) = -s;
- GSL_REAL (*z1) = -0.5 * b / a;
- GSL_IMAG (*z1) = s;
- return 2;
- }
- }
|