Fix index errors on world size > 0 #252
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awaelchli
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…ing-ai/litdata into bugfix/resume-index-error
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awaelchli
commented
Jul 22, 2024
| chunk_indexes_per_nodes: Any = [[] for _ in range(distributed_env.num_nodes)] | ||
| process_per_node = distributed_env.world_size // distributed_env.num_nodes | ||
| for rank, chunks_per_rank in enumerate(chunks_per_ranks): | ||
| chunk_indexes_per_nodes[0 if distributed_env.num_nodes == 1 else rank // process_per_node].extend( |
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Since chunks are now associated by worker and not rank (#237), the grouping by node here was still wrong. I extracted this grouping to a new function so I can more easily test it.
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| chunks_per_ranks = [[0, 1], [2, 3], [4, 5], [6, 7], [8, 9], [10, 11], [12, 13], [14, 15]] | ||
| shuffled_indexes = _intra_node_chunk_shuffle(_DistributedEnv(8, 7, 2), chunks_per_ranks, 42, 2) | ||
| assert shuffled_indexes == [5, 2, 0, 7, 6, 1, 3, 4, 13, 10, 8, 15, 14, 9, 11, 12] |
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Previously, the test was asserting the final output list which by itself is not very meaningful (apart from asserting it doesn't change from one version to the next).
I extended the test to show the other important properities:
- The shuffle is consistent across all ranks
- The shuffle is different from one epoch to the next.
awaelchli
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Fixes #251
Fixes:
I validated this fix using Multi-Node training in Lightning AI.