add support for int64 pointer in tiled_matmul kernel#1346
add support for int64 pointer in tiled_matmul kernel#1346Maxon081102 wants to merge 1 commit intofacebookresearch:mainfrom
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Thanks for the contribution. The change is very large, and this code is in best-effort maintenance, hence we can only accept changes if they don't add too much surface.
| pid = tl.program_id(0).to(tl.int64) | ||
| pid_k = tl.program_id(1).to(tl.int64) |
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I suspect these are the only two lines that differ wrt the original version, is that so?
What is the downside of always casting to int64 in the original kernel? Did you observe some performance regression?
| # Decide whether 32-bit address arithmetic can overflow; if so, use int64-safe kernel | ||
| INT32_MAX = (1 << 31) - 1 | ||
| def _dim_or_zero(xs, i): | ||
| return xs[i] if len(xs) > i else 0 | ||
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| use_int64 = False | ||
| for i in range(3): | ||
| Mi = max(0, _dim_or_zero(ms, i)) | ||
| Ni = max(0, _dim_or_zero(ns, i)) | ||
| Ki = max(0, _dim_or_zero(ks, i)) | ||
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| # A offsets | ||
| a_row_term = max(0, Mi - 1) * int(strides_am[i]) | ||
| a_col_term = max(0, Ki - 1) * int(strides_ak[i]) | ||
| # B offsets | ||
| b_row_term = max(0, Ki - 1) * int(strides_bk[i]) | ||
| b_col_term = max(0, Ni - 1) * int(strides_bn[i]) | ||
| # C offsets | ||
| c_row_term = max(0, Mi - 1) * int(strides_cm[i]) | ||
| c_col_term = max(0, Ni - 1) * int(strides_cn[i]) | ||
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| # Check per-term and per-address sums | ||
| if ( | ||
| a_row_term > INT32_MAX or a_col_term > INT32_MAX or | ||
| b_row_term > INT32_MAX or b_col_term > INT32_MAX or | ||
| c_row_term > INT32_MAX or c_col_term > INT32_MAX or | ||
| (a_row_term + a_col_term) > INT32_MAX or | ||
| (b_row_term + b_col_term) > INT32_MAX or | ||
| (c_row_term + c_col_term) > INT32_MAX | ||
| ): | ||
| use_int64 = True | ||
| break |
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What does this PR do?
Fixes runtime errors caused by pointer size mismatches in Triton kernels during very large matrix computations.
This PR introduces a new Triton kernel that uses int64 pointers and adds automatic kernel selection between the existing int32 kernel and the new int64 version.
The change ensures stable execution on long‑context LLM training tasks, preventing RuntimeError: Triton Error [CUDA]: an illegal memory access was encountered when matrix dimensions exceed int32 limits.