CMake and MKL

These don’t always play well.

Background

This post is mostly for my own future reference. The problem I had for about a full month was in linking MKL to my project’s build through CMake. The project I’m working on, OpenFAST, requires BLAS and LAPACK math libraries. Generally, Intel’s MKL libraries are better performing than the open source versions like OpenBLAS. However, working on a shared compute cluster means that I don’t have direct access to installing packages. The cluster I use has a package manager called module which modifies your $PATH to load and unload packages.

Problem

The CMake configuration in OpenFAST includes

find_package(BLAS required)
find_package(LAPACK required)

which should find the appropriate BLAS and LAPACK libraries, including MKL when it is loaded. For some odd reason this doesn’t work. However, inspecting the module which loads ifort shows that the environment variable $BLASLIB is set.

Solution

Thus, the math libraries can be passed explicitly to CMake with this command:

cmake .. -DBLAS_LIBRARIES=$BLASLIB -DLAPACK_LIBRARIES=$BLASLIB