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[zasdfgbnm]

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[zasdfgbnm]

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Description

• Fixed contiguity computation for allocation domains

• Improved handling of broadcast and reduction axes

• Correctly traverse dimensions from right to left

• Accurately compute stride dependencies for non-broadcast dims

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Changes walkthrough 📝

	Relevant files
Bug fix	fusion_cache_utils.cpp Fix contiguity logic in allocation domain                                csrc/runtime/fusion_cache_utils.cpp Rewrote contiguity computation to traverse from right to left Properly skip broadcast dimensions in stride calculation Handle reduction dimensions with std::nullopt as intended Use actual stride relationships to determine contiguity +37/-10

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PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 No relevant tests

⚡ Recommended focus areas for review Possible Issue The logic for computing contiguity has been significantly rewritten, but the new implementation may incorrectly handle cases where broadcast dimensions are present, potentially leading to incorrect contiguity flags due to index misalignment between the allocation domain and sizes/strides arrays. const auto [sizes, strides] = inferAllocationSizesAndStrides(tensor, tv, ExpressionEvaluator()); // Compute contiguity from right to left, based on allocation domain std::vector<std::optional<bool>> contiguity; auto allocation_domain = tv->getMaybeAllocationDomain(); contiguity.resize(allocation_domain.size()); int64_t index = sizes.size() - 1; // Start from rightmost in sizes/strides int64_t next_non_broadcast_shape = -1; int64_t next_non_broadcast_stride = -1; // Traverse allocation domain from right to left for (int64_t i = allocation_domain.size() - 1; i >= 0; i--) { auto id = allocation_domain[i]; if (id->isReduction()) { // Reduction has no corresponding entry in sizes/strides contiguity[i] = std::nullopt; } else if (id->isBroadcast()) { // Broadcast has entry in sizes/strides, but we ignore it contiguity[i] = std::nullopt; index--; // Skip the corresponding entry in sizes/strides } else { // Non-reduction, non-broadcast dimension int64_t current_stride = strides[index]; if (next_non_broadcast_shape == -1) { // This is the rightmost non-reduction non-broadcast dimension // Check if stride is 1 to determine contiguity contiguity[i] = (current_stride == 1); } else { // Check if current_stride == next_shape * next_stride // where next_shape/stride are from the next non-broadcast dimension contiguity[i] = (current_stride == next_non_broadcast_shape * next_non_broadcast_stride); } // Update next_non_broadcast_shape and next_non_broadcast_stride next_non_broadcast_shape = sizes[index]; next_non_broadcast_stride = strides[index]; index--; } } tv->setContiguity(contiguity); Logic Error The loop traverses the allocation domain from right to left, but the index into sizes/strides is decremented unconditionally for non-broadcast non-reduction dimensions. This may result in incorrect pairing of dimensions if there are multiple broadcast dimensions, leading to wrong contiguity calculations. for (int64_t i = allocation_domain.size() - 1; i >= 0; i--) { auto id = allocation_domain[i]; if (id->isReduction()) { // Reduction has no corresponding entry in sizes/strides contiguity[i] = std::nullopt; } else if (id->isBroadcast()) { // Broadcast has entry in sizes/strides, but we ignore it contiguity[i] = std::nullopt; index--; // Skip the corresponding entry in sizes/strides } else { // Non-reduction, non-broadcast dimension int64_t current_stride = strides[index]; if (next_non_broadcast_shape == -1) { // This is the rightmost non-reduction non-broadcast dimension // Check if stride is 1 to determine contiguity contiguity[i] = (current_stride == 1); } else { // Check if current_stride == next_shape * next_stride // where next_shape/stride are from the next non-broadcast dimension contiguity[i] = (current_stride == next_non_broadcast_shape * next_non_broadcast_stride); } // Update next_non_broadcast_shape and next_non_broadcast_stride next_non_broadcast_shape = sizes[index]; next_non_broadcast_stride = strides[index]; index--; }