Add fast path for contiguous innermost-dim reduction in var_mean.correction_out (#18791)#18791
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…ection_out (pytorch#18791) Summary: Add a fast path to the portable var_mean.correction_out kernel for the common case of reducing a contiguous tensor over its innermost (last) dimension with matching input/output dtypes. Both passes (sum for mean, then squared deviations for variance) use tight loops over contiguous memory that the compiler can auto-vectorize, bypassing the generic MapReduceOverDimListPlan infrastructure. Same activation conditions as the sum.IntList_out and mean.out fast paths: contiguous, single innermost dim, same dtype. Falls through to the original generic path otherwise. Reviewed By: manuelcandales, bruceshuyu Differential Revision: D100111209
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Summary:
Add a fast path to the portable var_mean.correction_out kernel for the common case of reducing a contiguous tensor over its innermost (last) dimension with matching input/output dtypes. Both passes (sum for mean, then squared deviations for variance) use tight loops over contiguous memory that the compiler can auto-vectorize, bypassing the generic MapReduceOverDimListPlan infrastructure.
Same activation conditions as the sum.IntList_out and mean.out fast paths: contiguous, single innermost dim, same dtype. Falls through to the original generic path otherwise.
Reviewed By: manuelcandales, bruceshuyu
Differential Revision: D100111209