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/* ode-initval/cstd.c
*
* 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.
*/
#include <config.h>
#include <stdlib.h>
#include <math.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_odeiv.h>
typedef struct
{
double eps_abs;
double eps_rel;
double a_y;
double a_dydt;
}
std_control_state_t;
static void *
std_control_alloc (void)
{
std_control_state_t * s =
(std_control_state_t *) malloc (sizeof(std_control_state_t));
if (s == 0)
{
GSL_ERROR_NULL ("failed to allocate space for std_control_state",
GSL_ENOMEM);
}
return s;
}
static int
std_control_init (void * vstate,
double eps_abs, double eps_rel, double a_y, double a_dydt)
{
std_control_state_t * s = (std_control_state_t *) vstate;
if (eps_abs < 0)
{
GSL_ERROR ("eps_abs is negative", GSL_EINVAL);
}
else if (eps_rel < 0)
{
GSL_ERROR ("eps_rel is negative", GSL_EINVAL);
}
else if (a_y < 0)
{
GSL_ERROR ("a_y is negative", GSL_EINVAL);
}
else if (a_dydt < 0)
{
GSL_ERROR ("a_dydt is negative", GSL_EINVAL);
}
s->eps_rel = eps_rel;
s->eps_abs = eps_abs;
s->a_y = a_y;
s->a_dydt = a_dydt;
return GSL_SUCCESS;
}
static int
std_control_hadjust(void * vstate, size_t dim, unsigned int ord, const double y[], const double yerr[], const double yp[], double * h)
{
std_control_state_t *state = (std_control_state_t *) vstate;
const double eps_abs = state->eps_abs;
const double eps_rel = state->eps_rel;
const double a_y = state->a_y;
const double a_dydt = state->a_dydt;
const double S = 0.9;
const double h_old = *h;
double rmax = DBL_MIN;
size_t i;
for(i=0; i<dim; i++) {
const double D0 =
eps_rel * (a_y * fabs(y[i]) + a_dydt * fabs(h_old * yp[i])) + eps_abs;
const double r = fabs(yerr[i]) / fabs(D0);
rmax = GSL_MAX_DBL(r, rmax);
}
if(rmax > 1.1) {
/* decrease step, no more than factor of 5, but a fraction S more
than scaling suggests (for better accuracy) */
double r = S / pow(rmax, 1.0/ord);
if (r < 0.2)
r = 0.2;
*h = r * h_old;
return GSL_ODEIV_HADJ_DEC;
}
else if(rmax < 0.5) {
/* increase step, no more than factor of 5 */
double r = S / pow(rmax, 1.0/(ord+1.0));
if (r > 5.0)
r = 5.0;
if (r < 1.0) /* don't allow any decrease caused by S<1 */
r = 1.0;
*h = r * h_old;
return GSL_ODEIV_HADJ_INC;
}
else {
/* no change */
return GSL_ODEIV_HADJ_NIL;
}
}
static void
std_control_free (void * vstate)
{
std_control_state_t *state = (std_control_state_t *) vstate;
free (state);
}
static const gsl_odeiv_control_type std_control_type =
{"standard", /* name */
&std_control_alloc,
&std_control_init,
&std_control_hadjust,
&std_control_free};
const gsl_odeiv_control_type *gsl_odeiv_control_standard = &std_control_type;
gsl_odeiv_control *
gsl_odeiv_control_standard_new(double eps_abs, double eps_rel,
double a_y, double a_dydt)
{
gsl_odeiv_control * c =
gsl_odeiv_control_alloc (gsl_odeiv_control_standard);
int status = gsl_odeiv_control_init (c, eps_abs, eps_rel, a_y, a_dydt);
if (status != GSL_SUCCESS)
{
gsl_odeiv_control_free (c);
GSL_ERROR_NULL ("error trying to initialize control", status);
}
return c;
}
gsl_odeiv_control *
gsl_odeiv_control_y_new(double eps_abs, double eps_rel)
{
return gsl_odeiv_control_standard_new(eps_abs, eps_rel, 1.0, 0.0);
}
gsl_odeiv_control *
gsl_odeiv_control_yp_new(double eps_abs, double eps_rel)
{
return gsl_odeiv_control_standard_new(eps_abs, eps_rel, 0.0, 1.0);
}
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