Nx performance

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Kyle White

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Sep 19, 2022, 8:55:22 PM9/19/22
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Hi,

I'm just getting my feet wet with both Elixir and Nx and came across a striking performance difference between Nx and the Stream module for a computation.

My simple example is compute the sum of all odd numbers from 1 to N. Nx is taking ~20x as long as doing the computation without Nx.

Is there some way to optimize this for Nx? any tips? I'm of course looking to do a lot more with Nx but want to be sure I understand how to use it correctly first.

My example code is attached.

Thanks,
Kyle

comparison.exs

Sean Moriarity

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Sep 19, 2022, 8:58:47 PM9/19/22
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Hi Kyle,

You're running Nx with the default backend (BinaryBackend), which is pure Elixir and very, very slow. You should try EXLA or Torchx as your backend. Try re-running your benchmark, but instead calling `Nx.Defn.global_default_options(compiler: EXLA)` before the call to `Benchmark.add_nx`

Sean

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Kyle White

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Sep 19, 2022, 9:19:05 PM9/19/22
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Hi Sean,

Thanks for the quick response on the lame question -- I should have read more of the docs before coming here. ~600ms down to <5 after compilation. Thanks!

Kyle

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smoria...@gmail.com

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Sep 19, 2022, 11:04:47 PM9/19/22
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No problem, glad to help, and glad you’re seeing speedups now! 🙂

Sean

On Sep 19, 2022, at 9:19 PM, Kyle White <kylew...@gmail.com> wrote:


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