[FSDPv2] Shard on the maximal dim of weights #7134
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JackCaoG
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May 29, 2024
| @@ -113,7 +118,8 @@ def __init__( | |||
| for param in module.parameters(): | |||
| if torch_xla._XLAC._get_xla_sharding_spec(param) != "": | |||
| continue | |||
| spmd.mark_sharding(param, mesh, _prepare_spmd_partition_spec(param)) | |||
| spmd.mark_sharding( | |||
| param, mesh, _prepare_spmd_partition_spec(param, shard_maximal=True)) | |||
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should we make it configureable?
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No, not necessary... It shouldn't matter to the user...
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ok I think I get it.. We need to do a all-gather anyway before entering the layer and only one dimension is being sharded.
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Yea, that's right. If the 0th dim is like size of 8 (MoE) and we are sharding it on v5p-2048, it will be a disaster.
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JackCaoG
approved these changes
May 29, 2024
|
Thanks Jack for approving the change. |
|
Skip GPU to move fast. |
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Summary:
This pull request makes FSDPv2 to shard on the maximal dim of weights instead of the 0th dim.
Test Plan:
XLA_USE_SPMD=1 PJRT_DEVICE=TPU python test/spmd/test_fsdp_v2.py