Shouldn't there be `restrict` keyword at parameters in `VectorInnerProduct()`?
Problem
https://github.com/pgvector/pgvector/blob/2627c5ff775ae6d7aef0c430121ccf857842d2f2/src/vector.c#L592-L602 [code block] https://en.wikipedia.org/wiki/Restrict
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1 Fix
Add `restrict` Keyword to Parameters in VectorInnerProduct()
The absence of the `restrict` keyword in the parameters of the VectorInnerProduct() function can lead to unintended aliasing issues. This can result in suboptimal performance due to the compiler being unable to make certain optimizations. The `restrict` keyword informs the compiler that the pointers passed to the function do not alias, allowing for more efficient memory access and better optimization during compilation.
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- 1
Modify Function Signature
Update the function signature of VectorInnerProduct() to include the `restrict` keyword for its pointer parameters. This will help the compiler optimize the function by assuming that the pointers do not point to the same memory location.
cvoid VectorInnerProduct(const float * restrict a, const float * restrict b, float * restrict result) - 2
Review Function Implementation
Ensure that the function implementation of VectorInnerProduct() correctly handles the new signature. Check for any assumptions made about the input parameters and verify that they align with the use of `restrict`.
cfor (size_t i = 0; i < n; i++) { result[i] = a[i] * b[i]; } - 3
Run Unit Tests
Execute existing unit tests that cover the VectorInnerProduct() function to ensure that the changes do not introduce any regressions. If necessary, add new tests to validate the behavior with the `restrict` keyword.
cassert(VectorInnerProduct(a, b, result) == expected_result); - 4
Benchmark Performance
Conduct performance benchmarks before and after the modification to quantify the impact of adding the `restrict` keyword. This will help in understanding the performance improvements gained from the change.
ctime_taken = benchmark(VectorInnerProduct, a, b, result); - 5
Update Documentation
Update any relevant documentation to reflect the changes made to the function signature and the implications of using the `restrict` keyword. This ensures that future developers understand the purpose of the keyword in this context.
c// VectorInnerProduct computes the inner product of two vectors with no aliasing.
Validation
Confirm that all unit tests pass successfully and that performance benchmarks show an improvement in execution time. Additionally, review the documentation to ensure it accurately reflects the changes.
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Environment
Submitted by
Alex Chen
2450 rep