int main(void)
{
int i,j;
float eps,hdid,hnext,htry,x=1.0,*y,*dydx,*dysav,*ysav,*yscal;
y=vector(1,N);
dydx=vector(1,N);
dysav=vector(1,N);
ysav=vector(1,N);
yscal=vector(1,N);
ysav[1]=bessj0(x);
ysav[2]=bessj1(x);
ysav[3]=bessj(2,x);
ysav[4]=bessj(3,x);
derivs(x,ysav,dysav);
for (i=1;i<=N;i++) yscal[i]=1.0;
htry=0.6;
printf("%10s %11s %12s %13s\n","eps","htry","hdid","hnext");
for (i=1;i<=15;i++) {
eps=exp((double) -i);
x=1.0;
for (j=1;j<=N;j++) {
y[j]=ysav[j];
dydx[j]=dysav[j];
}
rkqs(y,dydx,N,&x,htry,eps,yscal,&hdid,&hnext,derivs);
printf("%13f %8.2f %14.6f %12.6f \n",eps,htry,hdid,hnext);
}
free_vector(yscal,1,N);
free_vector(ysav,1,N);
free_vector(dysav,1,N);
free_vector(dydx,1,N);
free_vector(y,1,N);
return 0;
}
void RungeKuttaSolver::ode_rk(int nvar, double x1, double x2, double eps, double h1, double hmin, int *nok, int *nbad, RungeKuttaEquation *Equations[])
{
int nstp,i;
double xsav, x, hnext, hdid, h; // DJA: h is the current time step value
double *yscal,*y,*dydx;
yscal=new_vector(1,nvar);
y=new_vector(1,nvar);
dydx=new_vector(1,nvar);
x=x1;
h=SIGN(h1,x2-x1);
*nok = (*nbad) = kount = 0;
for (i = 1; i <= nvar ; i++)
y[i] = Equations[i]->InitialY;
if (kmax > 0) xsav=x-dxsav*2.0;
for (nstp=1;nstp<=MAXSTP;nstp++)
{
// (*derivs)(x,y,dydx); DJA: This is the old call which we've replaced with the following two lines
for (i = 1; i <= nvar ; i++)
dydx[i] = Equations[i]->GetDerivative(y[i], y[5]);
for (i=1;i<=nvar;i++)
yscal[i]=fabs(y[i])+fabs(dydx[i]*h)+TINY;
if (kmax > 0 && kount < kmax-1 && fabs(x-xsav) > fabs(dxsav))
{
xp[++kount]=x;
for (i=1;i<=nvar;i++) yp[i][kount]=y[i];
xsav=x;
}
if ((x+h-x2)*(x+h-x1) > 0.0)
h=x2-x;
rkqs(y,dydx,nvar,&x,h,eps,yscal,&hdid,&hnext,Equations);
if (hdid == h)
++(*nok);
else
++(*nbad);
if ((x-x2)*(x2-x1) >= 0.0)
{
for (i=1;i<=nvar;i++)
Equations[i]->InitialY = y[i];
if (kmax)
{
xp[++kount]=x;
for (i=1;i<=nvar;i++)
yp[i][kount]=y[i];
}
delete_vector(dydx,1,nvar);
delete_vector(y,1,nvar);
delete_vector(yscal,1,nvar);
return;
}
// printf("hnext %f hmin %f\n",hnext,hmin);
if (fabs(hnext) <= hmin)
{
nrerror("Step size too small in odeint");
}
h=hnext;
}
nrerror("Too many steps in routine odeint");
}
