[Help-gsl] performing several integrations for different parameter values (gsl_odeiv2)

[Altro]

Hi,

I have to resolve a system of ODE for 5 values of a parameter (for 
example "h").
I implemented the following pseudo-code, but something is wrong:

typedef struct {double h; double p; double **J; other parameters } 
structure;
//store the parameter values in a vector pointed by h
h[0]=0.1;
h[1]=0.2;
...
h[4]=0.5;
structure S;
...
//definition of ODE system
gsl_odeiv2_system sys = {func, NULL, dimension, &S};
for (i=0; i<5; i++){
    S.h = h[i];    //assign to S.h one of the  5 values.
    gsl_odeiv2_step * s = gsl_odeiv2_step_alloc(stepper, 4);
    gsl_odeiv2_control * c = gsl_odeiv2_control_y_new (1e-6, 1e-6);
    gsl_odeiv2_evolve * e = gsl_odeiv2_evolve_alloc (4);
    for (j=1; j<=400; j++){
        while (t<t2) {
           //call a function that compute the jabobian at each step
           updatejacobian(S, x);
           //perform a time step
           gsl_status = gsl_odeiv2_evolve_apply (e, c, s, &sys, &t, t2, 
&h, X);
        }
        t=0;
    }
    gsl_odeiv2_evolve_free (e);
    gsl_odeiv2_control_free (c);
    gsl_odeiv2_step_free (s);
}

where:
updatejacobian (structure S, double *x){
    S.J[0][0] = S.r * sin(x[4*S.p+3]) * (1 - 2*S.h) - 1;
    .....
}

This program should perform 5 integrations of the same set of ODEs 
varing parameters S.h (I do not write the entire code, of course). The 
program behave well until i=0, but at the first increment I receive error:

Program received signal SIGSEGV, Segmentation fault.
0x0000000000401537 in updatejacobian (S=..., x=0x6045b0) at file.c:57
57        S.J[0][0] = S.r *sin(x[4*S.p+3]) * (1 - 2*S.h) - 1;


The program works well also setting S.h (e.g. S.h=0.2) and cutting the
cicle for (i=0; i<5; i++).

Do you understand what's wrong?
Thanks,

A.