Fortran 90, program with runge-kutta & adams-bashforth subroutines

[vs_3477]

Hello,

I was hoping someone could help me with a programming problem in fortran 90. I have to come up with a program that contains a subroutine to perform a single-step of the runge-kutta fourth order method. And then a subroutine that calls from the runge-kutta method and performs a single-step of the adams-bashforth multi-step method. And then I have to add in a subroutine which will perform a single-step of the modified Hamming's fourth order predictor-corrector method, again calling the results from the runge-kutta step. Finally I have to put in a function, to be used by all of the above methods which will calculate the differential equation for given values y and x. I have been having problems doing this for a while now because I think I'm making a couple of small errors which I can't seem to find/fix. I think I have got the runge-kutta bit ok but I can't seem to call on it correctly, and I'm also having problems saving the old value of y so that I can use it later. Any help anyone could give me on this would be greatly appreciated, or even links to where I could find examples of a similar code.

Thank you for you time and help

[jal121387]

I just saw your post from 2009 about the odemod.f90 program. I was wondering if you ever got it figured out. I must be doing the same program. I need help writing the runge-kutta and adams-bashforth methods.