Incorporate coalesce analysis in codegen #153751
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This was referenced May 16, 2025
🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/153751
Note: Links to docs will display an error until the docs builds have been completed. ❗ 1 Active SEVsThere are 1 currently active SEVs. If your PR is affected, please view them below: ❌ 17 New Failures, 2 Unrelated FailuresAs of commit 948321e with merge base 5d316ce ( NEW FAILURES - The following jobs have failed:
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Stack from ghstack (oldest at bottom):
This pr uses the coalescing information in generating a tiling. The previous tiling heuristic would have each dependency generate a tiling. Then, we sum up the score for each generated tiling, preferring any 2d tiling over the default. The new tiling heuristics scores each tiling by its global coalesced memory. This gives both a potentially better tiling (especially for more complicated, 3d patterns) as well as information we can use in generating block sizes.
In triton heuristics, for generating 3d tiled reductions, we take the same total block size that the 2d reduction would use, then distribute the block according to whichever block coalesces the most memory.
The motivating kernel is in #149982 which is a 32 element reduction. A smaller version of it is here. We need to run this kernel once in the forward per linear layer on a contiguous tensor, and once in the backward on a transposed tensor.
While the contiguous kernel has coalesced accesses, and is performant on master, the transposed version accesses uncoalesced memory on main and is ~2.8x slower. See, this full log from the above repro. Now, with this PR, it is only ~1.15x slower. See the updated log.
cc @voznesenskym @penguinwu @EikanWang @jgong5 @Guobing-Chen @XiaobingSuper @zhuhaozhe @blzheng @wenzhe-nrv @jiayisunx @ipiszy @chenyang78 @kadeng @muchulee8 @amjames @chauhang @aakhundov