Hello friends. I have a problem in FORTRAN programming. I need to divide a larg zone into several parts but I can't define a matrix bigger than (4*1600*500) because the program fails and There is not any message to understand the reason of the error. I realy dont know what I have to do. PLEASE HELP ME. Thank you very much. By.

You are probably having a memory problem.

1)put the matrix into its own named common block

2)If that does not work, you might try building it as a 64bit code.

Hello.

Thank you very much for your help but I didn't understand what exactly I have to do know. Please explain me more. As I asked my friends, It is a common problem in CFD programming but none of them could help me. Thank again.

Best regards. Behafarid

what is your compiler and platform and your physical memory size, i think it is not serious problem and resolved very easily.

First of all, let me do a simple calculation:

4*1600*500 = 3200000 coeficients

assuming double precision (8 bytes per coeficient) -- and that you're not spending more memory in other parts of your program -- you'll need

3200000 * 8 = 25600000 Bytes

or about 24.4 MBytes

(if I'm not wrong in my calc) It doesn't seem to be hard allocate such array.

Is this array inside a subroutine? You can be running into stack size problems.

Have you tried to allocate this array statically or dynamically?

Regards

Renato.

Your problem is almost certainly stack size related. If you delare a variable inside a function, it'll use stack memory unless forced to use heap. To make it use heap memory, make it static. (e.g. in a COMMON block, defined in a DATA statement).

Try the following examples (using Fortran 90 sintax)

program foo real*8, allocatable :: a( n = 4*1600*500 allocate(a(n)) call SomeRoutine(a,n) deallocate(a) end program

subroutine SomeRoutine(a,n) ! You must avoid the use of the array size here. It always causes stack problems real*8 :: a(1) ... end subroutine

! --- END OF THE FIRST EXAMPLE ---

The same thing could be done with modules

module SomeData real*8, allocatable :: a( end module SomeData

program foo use SomeData n = 4*1600*500 allocate(a(n)) call SomeRoutine deallocate(a) end program

subroutine SomeRoutine use SomeData ... end subroutine

! --- END OF THE SECOND EXAMPLE ---

Here the array "a" is made accessible through the use of the module

Good lucky ;o)

Renato.