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fix: compute local block padding for dynamic splash indexer mask in CP #4950

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fix: compute local block padding for dynamic splash indexer mask in CP #4950

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6 changes: 4 additions & 2 deletions src/maxtext/layers/attention_op.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2111,8 +2111,10 @@ def wrap_flash_attention(
if indexer_mask is not None:
# Convert additive float mask (0.0=attend, negative=masked) to boolean mask for Tokamax splash kernel
indexer_mask = indexer_mask == 0.0
pad_q = mask_shape[0] - indexer_mask.shape[-2]
pad_kv = mask_shape[1] - indexer_mask.shape[-1]
padded_q_len = ((indexer_mask.shape[-2] + sa_config.block_q - 1) // sa_config.block_q) * sa_config.block_q
padded_kv_len = ((indexer_mask.shape[-1] + sa_config.block_kv - 1) // sa_config.block_kv) * sa_config.block_kv
pad_q = padded_q_len - indexer_mask.shape[-2]
pad_kv = padded_kv_len - indexer_mask.shape[-1]
if pad_q > 0 or pad_kv > 0:
pad_width = [(0, 0)] * (indexer_mask.ndim - 2) + [(0, pad_q), (0, pad_kv)]
indexer_mask = jnp.pad(
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3 changes: 0 additions & 3 deletions tests/unit/attention_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3480,9 +3480,6 @@ def test_tpu_dot_product_context_parallel_with_indexer(
"indexer_topk": 32,
},
)
@pytest.mark.skip(
reason="Indexer with all-gather context parallelism diverges from the dot_product reference; fix tracked in #4947."
)
@pytest.mark.tpu_only
def test_tpu_flash_attention_context_parallel_with_indexer(
self, context_parallel_load_balance, ici_context_parallelism=2, indexer_topk=256
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