[cutter]

Hi,

I tried to compile and optimize OpenFOAM for some new Core i7 CPUs with AVX2 and FMA. As far as I understand the default settings are using the general x86_64 instruction set. I forced the compiler to optimize for the extended instruction set by adding the -march=corei7 flag in /wmake/rules/linux64Gcc/c++Opt and /wmake/rules/linux64Gcc/cOpt. The compiler successfully used the settings, my first benchmarks did not show any noticeable effect though. I've been using a single thread for my cases in order to rule out MPI wait times and measure the raw CPU performance.

I've got two questions regarding this issue:

1. Is this the best or correct way to set the compiler flags?

2. What performance gain can be expected from optimized binaries?

Many Thanks
Cutter