Limit use of the indexing war for resize #3515
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H100 manually checked |
jacobhinkle
reviewed
Dec 3, 2024
csrc/id_model/indexing_traversal.cpp
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| // used rather than the local model. Here, since we just need to | ||
| // know if there are multiple dependent resize exprs, and loop | ||
| // promotion should not further add resize exprs, it is sufficient | ||
| // to analyze only the IDs of this expr only. |
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| // to analyze only the IDs of this expr only. | |
| // to analyze only the IDs of this expr. |
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!build |
jacobhinkle
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Dec 4, 2024
This was referenced Dec 4, 2024
naoyam
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Dec 9, 2024
This is a second attempt to fix #3505. The first attempt is #3515. As mentioned [here](#3505 (comment)), the first fix isn't sufficient when an expr has multiple resized inputs, like concat. The actual condition we need to check is between each producer and consumer pair, not between producers, so this second attempt is just changing how we check the condition.
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Fixes this error of #3505
The error happens when trying to use the indexing WAR for resize that was recently added (#3454). The war itself is limited, in particular it does not work with promoted loop IDs. The limitation should be fine for the RoPE scheduling I've been working on, but it's a real issue in general.
This PR avoids the issue by limiting the use of the WAR. Currently, the WAR is used whenever there's at least a single resize expr in a single math expr. That is actually overly pessimistic since the indexing issue only happens when there's multiple resize exprs that result in a cycle in the exact graph. For example, if there's only one resize, there must be no cycle, thus the indexing WAR is not necessary.
This PR attempts to limit the use of the WAR by doing a little deeper analysis. The added check should entirely disable the WAR for the current default scheduling, where resize is only allowed with fusion inputs, which means there can be no multiple dependent resize exprs in a single fusion.
The limitation of the WAR remains, but it does not matter for RoPE, and with this PR it should also not matter for general cases.