The parallel do is not faster than the serial do.

[eliopoulos]

Hi,

I have created a FORTRAN program and I would like to make it faster. So, I used the parallel do for my main loop. Although the CPU works at a much higher rate, the program is not faster, whatever number of threads I use. The speed also does not really change when I change the number of threads. Any advise?

[jimdempseyatthecove]

It would help if you would show the code.

There could be any number of reasons why your code isn't running any faster.

The usual culprits are:

1) Calling support routines that serialize (contain critical section) the code. For example calling RAN (or other random number generators), performing I/O, heavy memory allocations, among others

2) Too short of runtime for the application to amortize the startup

3) Using many more threads than is practical for a small application.

4) Oversubscription of threads

...

Without seeing the code (or a good sketch of the code) makes it difficult to offer suggtestions.

Jim Dempsey

[eliopoulos]

I would not like to share the code in public. Could you provide an e-mail address?

[jimdempseyatthecove]

jim.00.dempsey@gmail.com