Performance loss with gfortran on 64-bit Linux

[Tim Prince]

Steve Kargl wrote:
> On Fri, Jul 21, 2006 at 10:17:00PM -0700, Deji Akingunola wrote:
>> I've been running a 1-D atmospheric model with gfortran
>> and I'm observing it runs many orders slower in 64-bit
>> than it does in 32 bit mode. The system is x86_64 Fedora
>> rawhide (which contains the latest gfortran from the 4.1 tree).
>>
> 
> Can you add -pg to the gfortran builds and look at the 
> profiled output?
> 
   Where are the instructions on how to test with your data set?
I would have thought that "many orders of magnitude" would have meant a 
factor of a million or so, which I would not have the patience to verify.
As Steve hints, some -pg results might help us guess why you apparently 
did not find it useful to turn on any optimizations like -O2, 
-funroll-loops, or -ftree-vectorize, even though you chose extremely 
aggressive settings for commercial compilers.