Why is Julia asking for AVX instructions on Ubuntu 14.04?

Question

On my Ubuntu 14.04 box, Julia is complaining that my machine doesn't support AVX instructions. What may be the reason for this?

Answer 1

"AVX instructions" are extensions to the basic x86 instruction set, and are relatively new (2011).

Julia comes with OpenBLAS for faster linear algebra. It can compile different code pathways based on processor type, and apparently your CPU is too old to support AVX instructions (which the julialang.org build apparently assumes will be available).

You can either ignore the message, or build from source. What CPU do you have?

Answer 2

The OpenBLAS library, used by Julia, is warning you that it cannot use its most efficient implementation of linear algebra operations, so it is falling back to the version optimised for the older Nehalem processor. You can safely ignore this warning.