I work on CFD software. We're well aware of this in my work, but the reality is that all our big corporate clients use Intel hardware. We already tell people to set those environment variables in our documentation.<p>> Avoid the Intel compiler. There are other compilers with similar or better performance.<p>This is not really true IMO, but even as an aside, the Intel compiler has the enormous advantage of being available cross platform. So we can use it on Linux and Windows, and provides MPI cross platform. We upgrade fairly regularly and that provides us with less work.<p>My own tests found that PGI compiler performance was worse than Intel for C++, and that now appears to have been discontinued on Windows anyway with NVidia's new HPC compiler suite replacing it. GNU can run everywhere, but performance is around 2.5x worse on Linux for our application use case because it doesn't perform many of the optimisations that Intel does. We use MSVC on Windows just because everyone can have a license, and performance is much worse.<p>The other thing is that MKL is pretty stable and gets updated. If I use an open source BLAS/LAPACK implementation - sure, it works, and it may even give better performance! But it's not guaranteed to get updates beyond a couple of years, and plenty of implementations are also only partial. We pay Intel a lot of money for the lack of hassle, basically.