performance difference between 32 and 64bits versions

Numerical methods and mathematical models of Elmer
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performance difference between 32 and 64bits versions

Post by Kankreu » 09 Jul 2014, 09:24

Hi all,

I ran elmer 32 and 64 on a same machine (Win8 64bits, 4 cores, 6Gb). Elmer7.0-rev6064-2013-02-15 (32bits) & Elmer7.0-rev5884-win64.
The case is attached, nothing special, just a clamp beam, not too big: 43k elements.
Here is the strange behaviour (machine is not overloaded as cpu and real times are equal):
The run in 32bits takes 41 sec
The run in 64bits takes 82 sec
both with linear elements (comment line 37 of attached sif file),with respectively 885 and 905Mb of memory.
The run with quad elements doesn't pass in 32bits.
In 64bits, it takes 12000 sec with almost 6Gb and 26Gb in Private set memory!!!

At the end, the results are quite similar (6% diff on Max Von Misses or abs_displacement).
Is it normal that the ep file doesn't contains more results? or is it due to the quad formulation in Elmer (I like that "Element = p:2").

1) why is the 64bits taking more time in linear?
I realize that i'm not using (needing) the 64bits capabilities for that model. Is the compilation not optimized?

2) For the 2nd case, I ran some benchmark before (with a simpler beam with different mesh quality to compare with analytic solution) and I didn't observe so much time difference between linear and quad. Is it due to the solver (direct) I selected?

Thanks for your comment,
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