Speed up maxout by exploiting parallelism better #579
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Use `which` to select the max elements from the original array and check this against the expected maxout output.
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Added a test which checks |
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@explosion-bot please test_gpu |
URL: https://buildkite.com/explosion-ai/thinc-gpu-test-suite/builds/16 |
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The test failure is unrelated, but interesting (inconsistent results in the grad scaler test). |
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@explosion-bot please test_gpu |
URL: https://buildkite.com/explosion-ai/thinc-gpu-test-suite/builds/17 |
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I was profiling the parser refactor and noticed that the maxout kernel is taking more time than I expected:
The maximum amount of parallelism by the kernel is determined by its batch size. However, this leaves the GPU underused. E.g. by default our amount of parallelism is nr_blocks: 128 * nr_threads_per_block: 128 = 16384, which is much larger than the typical batch size.
This PR changes the maxout kernel to parallelize at the output level (each thread computes one output). This makes the maxout kernel about 4.7 times faster with a batch size of 1024 on a RTX 2060 Super:
I haven't updated the backprop variant yet, since it barely appears in the profiles.