IcoFoam erformace on 32 bit vs 64 bit

henry · August 25, 2005, 10:57

We have found that for most but not all cases running 64bit on the Opteron is faster than running 32bit but the difference is rarely greater than 15%. I doubt you will see much improvement by changing the optimisation flags but we haven't tested all the options.

maka · August 25, 2005, 11:09

A friend suggested that usually -tp k8-64 may give good improvement but I have to admit that yet I can not find the file where, I should use this option. I'm looking in $HOME/OpenFOAM/OpenFOAM-1.1/wmake.

Can you give me some hint of where is the file that controls the compilation options.

Many thanks,
Maka

henry · August 25, 2005, 11:14

The compilation options for each platform are in OpenFOAM-1.?/wmake/rules. For version 1.1 you will want to put your optimisation options in the file linuxAMD64/c++Opt and for version 1.2 in linuxAMD64Gcc4/c++Opt if you are using gcc-4.0.1 supplied with the release.

August 25, 2005, 10:57	We have found that for most bu	#1
henry Senior Member Join Date: Mar 2009 Posts: 854 Rep Power: 22	We have found that for most but not all cases running 64bit on the Opteron is faster than running 32bit but the difference is rarely greater than 15%. I doubt you will see much improvement by changing the optimisation flags but we haven't tested all the options.

August 25, 2005, 11:09	A friend suggested that usuall	#2
maka Senior Member Maka Mohu Join Date: Mar 2009 Posts: 305 Rep Power: 18	A friend suggested that usually -tp k8-64 may give good improvement but I have to admit that yet I can not find the file where, I should use this option. I'm looking in $HOME/OpenFOAM/OpenFOAM-1.1/wmake. Can you give me some hint of where is the file that controls the compilation options. Many thanks, Maka

August 25, 2005, 11:14	The compilation options for ea	#3
henry Senior Member Join Date: Mar 2009 Posts: 854 Rep Power: 22	The compilation options for each platform are in OpenFOAM-1.?/wmake/rules. For version 1.1 you will want to put your optimisation options in the file linuxAMD64/c++Opt and for version 1.2 in linuxAMD64Gcc4/c++Opt if you are using gcc-4.0.1 supplied with the release.

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