Fix integer overflows in attention & cache ops #1514
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zhuohan123
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Oct 31, 2023
| + head_offset * block_size | ||
| + block_offset; | ||
| const int64_t tgt_key_idx = block_idx * num_heads * (head_size / x) * block_size * x | ||
| + head_idx * (head_size / x) * block_size * x |
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All the numbers in this expression is int: head_idx * (head_size / x) * block_size * x. For safety, should we change all numbers to int64_t? I think this should only bring negligible overhead but I'm not 100% sure.
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I think this is ok because block_idx is int64_t. If I understand correctly, the only expression that can cause overflow is block_idx * num_heads * (head_size / x) * block_size * x. Since block_idx is int64_t, this expression and the subsequent additions to this value are all evaluated as int64_t.
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@zhuohan123 Does this relieve your concern?
|
Thanks for the quick fix!!! |
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Fixes #1486
This PR fixes the overflows in paged attention & cache ops when the number of blocks is huge.