1 /* multimin/vector_bfgs.c
3 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Fabrice Rossi
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3 of the License, or (at
8 * your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 /* vector_bfgs.c -- Limited memory Broyden-Fletcher-Goldfarb-Shanno method */
22 /* Modified by Brian Gough to use single iteration structure */
25 #include <gsl/gsl_multimin.h>
26 #include <gsl/gsl_blas.h>
28 #include "directional_minimize.c"
50 vector_bfgs_alloc (void *vstate, size_t n)
52 vector_bfgs_state_t *state = (vector_bfgs_state_t *) vstate;
54 state->x1 = gsl_vector_calloc (n);
58 GSL_ERROR ("failed to allocate space for x1", GSL_ENOMEM);
61 state->dx1 = gsl_vector_calloc (n);
65 gsl_vector_free (state->x1);
66 GSL_ERROR ("failed to allocate space for dx1", GSL_ENOMEM);
69 state->x2 = gsl_vector_calloc (n);
73 gsl_vector_free (state->dx1);
74 gsl_vector_free (state->x1);
75 GSL_ERROR ("failed to allocate space for x2", GSL_ENOMEM);
78 state->p = gsl_vector_calloc (n);
82 gsl_vector_free (state->x2);
83 gsl_vector_free (state->dx1);
84 gsl_vector_free (state->x1);
85 GSL_ERROR ("failed to allocate space for p", GSL_ENOMEM);
88 state->x0 = gsl_vector_calloc (n);
92 gsl_vector_free (state->p);
93 gsl_vector_free (state->x2);
94 gsl_vector_free (state->dx1);
95 gsl_vector_free (state->x1);
96 GSL_ERROR ("failed to allocate space for g0", GSL_ENOMEM);
99 state->g0 = gsl_vector_calloc (n);
103 gsl_vector_free (state->x0);
104 gsl_vector_free (state->p);
105 gsl_vector_free (state->x2);
106 gsl_vector_free (state->dx1);
107 gsl_vector_free (state->x1);
108 GSL_ERROR ("failed to allocate space for g0", GSL_ENOMEM);
111 state->dx0 = gsl_vector_calloc (n);
115 gsl_vector_free (state->g0);
116 gsl_vector_free (state->x0);
117 gsl_vector_free (state->p);
118 gsl_vector_free (state->x2);
119 gsl_vector_free (state->dx1);
120 gsl_vector_free (state->x1);
121 GSL_ERROR ("failed to allocate space for g0", GSL_ENOMEM);
124 state->dg0 = gsl_vector_calloc (n);
128 gsl_vector_free (state->dx0);
129 gsl_vector_free (state->g0);
130 gsl_vector_free (state->x0);
131 gsl_vector_free (state->p);
132 gsl_vector_free (state->x2);
133 gsl_vector_free (state->dx1);
134 gsl_vector_free (state->x1);
135 GSL_ERROR ("failed to allocate space for g0", GSL_ENOMEM);
142 vector_bfgs_set (void *vstate, gsl_multimin_function_fdf * fdf,
143 const gsl_vector * x, double *f, gsl_vector * gradient,
144 double step_size, double tol)
146 vector_bfgs_state_t *state = (vector_bfgs_state_t *) vstate;
149 state->step = step_size;
150 state->max_step = step_size;
153 GSL_MULTIMIN_FN_EVAL_F_DF (fdf, x, f, gradient);
155 /* Use the gradient as the initial direction */
157 gsl_vector_memcpy (state->x0, x);
158 gsl_vector_memcpy (state->p, gradient);
159 gsl_vector_memcpy (state->g0, gradient);
162 double gnorm = gsl_blas_dnrm2 (gradient);
163 state->pnorm = gnorm;
164 state->g0norm = gnorm;
171 vector_bfgs_free (void *vstate)
173 vector_bfgs_state_t *state = (vector_bfgs_state_t *) vstate;
175 gsl_vector_free (state->dg0);
176 gsl_vector_free (state->dx0);
177 gsl_vector_free (state->g0);
178 gsl_vector_free (state->x0);
179 gsl_vector_free (state->p);
180 gsl_vector_free (state->x2);
181 gsl_vector_free (state->dx1);
182 gsl_vector_free (state->x1);
186 vector_bfgs_restart (void *vstate)
188 vector_bfgs_state_t *state = (vector_bfgs_state_t *) vstate;
195 vector_bfgs_iterate (void *vstate, gsl_multimin_function_fdf * fdf,
196 gsl_vector * x, double *f,
197 gsl_vector * gradient, gsl_vector * dx)
199 vector_bfgs_state_t *state = (vector_bfgs_state_t *) vstate;
201 gsl_vector *x1 = state->x1;
202 gsl_vector *dx1 = state->dx1;
203 gsl_vector *x2 = state->x2;
204 gsl_vector *p = state->p;
205 gsl_vector *g0 = state->g0;
206 gsl_vector *x0 = state->x0;
208 double pnorm = state->pnorm;
209 double g0norm = state->g0norm;
211 double fa = *f, fb, fc;
213 double stepa = 0.0, stepb, stepc = state->step, tol = state->tol;
218 if (pnorm == 0.0 || g0norm == 0.0)
220 gsl_vector_set_zero (dx);
224 /* Determine which direction is downhill, +p or -p */
226 gsl_blas_ddot (p, gradient, &pg);
228 dir = (pg >= 0.0) ? +1.0 : -1.0;
230 /* Compute new trial point at x_c= x - step * p, where p is the
233 take_step (x, p, stepc, dir / pnorm, x1, dx);
235 /* Evaluate function and gradient at new point xc */
237 fc = GSL_MULTIMIN_FN_EVAL_F (fdf, x1);
241 /* Success, reduced the function value */
242 state->step = stepc * 2.0;
244 gsl_vector_memcpy (x, x1);
245 GSL_MULTIMIN_FN_EVAL_DF (fdf, x1, gradient);
250 printf ("got stepc = %g fc = %g\n", stepc, fc);
253 /* Do a line minimisation in the region (xa,fa) (xc,fc) to find an
254 intermediate (xb,fb) satisifying fa > fb < fc. Choose an initial
255 xb based on parabolic interpolation */
257 intermediate_point (fdf, x, p, dir / pnorm, pg,
258 stepa, stepc, fa, fc, x1, dx1, gradient, &stepb, &fb);
265 minimize (fdf, x, p, dir / pnorm,
266 stepa, stepb, stepc, fa, fb, fc, tol,
267 x1, dx1, x2, dx, gradient, &(state->step), f, &g1norm);
269 gsl_vector_memcpy (x, x2);
271 /* Choose a new direction for the next step */
273 state->iter = (state->iter + 1) % x->size;
275 if (state->iter == 0)
277 gsl_vector_memcpy (p, gradient);
278 state->pnorm = g1norm;
282 /* This is the BFGS update: */
283 /* p' = g1 - A dx - B dg */
284 /* A = - (1+ dg.dg/dx.dg) B + dg.g/dx.dg */
287 gsl_vector *dx0 = state->dx0;
288 gsl_vector *dg0 = state->dg0;
290 double dxg, dgg, dxdg, dgnorm, A, B;
293 gsl_vector_memcpy (dx0, x);
294 gsl_blas_daxpy (-1.0, x0, dx0);
297 gsl_vector_memcpy (dg0, gradient);
298 gsl_blas_daxpy (-1.0, g0, dg0);
300 gsl_blas_ddot (dx0, gradient, &dxg);
301 gsl_blas_ddot (dg0, gradient, &dgg);
302 gsl_blas_ddot (dx0, dg0, &dxdg);
304 dgnorm = gsl_blas_dnrm2 (dg0);
309 A = -(1.0 + dgnorm * dgnorm / dxdg) * B + dgg / dxdg;
317 gsl_vector_memcpy (p, gradient);
318 gsl_blas_daxpy (-A, dx0, p);
319 gsl_blas_daxpy (-B, dg0, p);
321 state->pnorm = gsl_blas_dnrm2 (p);
324 gsl_vector_memcpy (g0, gradient);
325 gsl_vector_memcpy (x0, x);
326 state->g0norm = gsl_blas_dnrm2 (g0);
329 printf ("updated directions\n");
331 gsl_vector_fprintf (stdout, p, "%g");
333 gsl_vector_fprintf (stdout, gradient, "%g");
339 static const gsl_multimin_fdfminimizer_type vector_bfgs_type = {
340 "vector_bfgs", /* name */
341 sizeof (vector_bfgs_state_t),
344 &vector_bfgs_iterate,
345 &vector_bfgs_restart,
349 const gsl_multimin_fdfminimizer_type
350 * gsl_multimin_fdfminimizer_vector_bfgs = &vector_bfgs_type;