In my experience, `icc/pc` and `ifort` give a significant speed boost for numerical code (on Intel hardware at least), but for more general purpose code it's no

In my experience, `icc/pc` and `ifort` give a significant speed boost for numerical code (on Intel hardware at least), but for more general purpose code it's not really very impressive. However, the related products like `ipp` and `mkl` are where Intel has a real advantage. My experience has been that `mkl` in particular is dramatically faster than vanilla LAPACK and friends and still quite a bit faster than more optimized variants like ATLAS. But, you don't need to use the Intel compilers to use those libraries, you can use them with gcc as well.