void getphi(double phi[], double Rho[], double r[], double dr[], int N)Output:
- phi[k]: electrostatic potential
on the grid
Input:
- Rho[k]:
for all grid points r[k]
- r[], dr[], N: standard grid information
Package your previous Poisson solver program into a routine of the
above prototype. Be sure to use ``interpolate'' to find the values on
the odd grid points after you have done the Runge-Kutta integration,
but before dividing Phi[k] by r[k]. Finally, because
your input is now Rho[k] 
4*pi*r[k]*r[k]*rho[k] instead of just rho[k],
you must modify ``derivs_Poisson'' so that it now contains a code
fragment of the form
.
.
dydx[1]=y[2]*dr[k];
dydx[2]=-Rho[k]/r[k]*dr[k];
.
.