Re: Similar systems, different performance of fortran code

[Victor Munoz <vmunoz@macul.ciencias.uchile.cl>]

To add more information about this:

I did a time profiling with gprof. The most important changes:

woody:
   time   seconds   seconds    calls   s/call   s/call  name    
    96.79     13.88    13.88      482     0.03     0.03  move_
     0.28     14.16     0.04      482     0.00     0.00  cpft_
     0.21     14.23     0.03      241     0.00     0.00  fields_    

sid:

 time   seconds   seconds    calls   s/call   s/call  name    
  99.25    107.86   107.86      482     0.22     0.22  move_
   0.58    108.49     0.63      241     0.00     0.00  fields_
   0.06    108.56     0.07      482     0.00     0.00  cpft_

So there is a huge difference in the subroutines move and fields. But move, 
for instance, is not very involved. It's a subroutine which calls no other
functions, just defines some variables, "common" lines, and such, 
and then iterates on the particles to move them. A series of matrices 
containing data for the particles are accessed element by element, 
divided by scalars, summed, etc. Nothing exotic. But these lines are the most 
often executed lines in the code, and are probably causing this huge 
difference in performance. But it's not obvious (to me at least) why...

Regards,

					Victor