Why Does TensorFlow Warn About Unsupported AVX/AVX2 Instructions, and How Can I Fix It?

"Your CPU supports instructions that this TensorFlow binary was not compiled to use: AVX AVX2"

Question:

I installed TensorFlow and received a warning message stating that my CPU supports instructions that the binary was not compiled to use. Why is this happening, and how can I fix it?

Answer:

What is the warning about?

AVX (Advanced Vector Extensions) and FMA (Fused Multiply-Add) are extensions to the x86 instruction set architecture that provide faster linear algebra computations like dot-products, matrix multiplies, and convolutions. Modern CPUs support these extensions, which can significantly speed up machine learning training.

Why isn't it used then?

The default TensorFlow distribution is designed for compatibility with as many CPUs as possible. It's intended to be used with GPUs, which are much faster than CPUs for large-scale training tasks.

What to do:

If you have a GPU:

• Ignore the warning using os.environ['TF_CPP_MIN_LOG_LEVEL'] = '2'.

If you don't have a GPU and want to use CPU:

• Build TensorFlow from source with AVX, AVX2, and FMA enabled. This requires using the Bazel build system, as described in the linked discussions. This should eliminate the warning and improve performance.

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