zhuqi-lucas opened a new pull request, #7962: URL: https://github.com/apache/arrow-rs/pull/7962
# Which issue does this PR close? This PR is follow-up for: https://github.com/apache/arrow-rs/pull/7937 I want to experiment the performance for Using word-level (u64) bit scanning: Details: https://github.com/apache/arrow-rs/pull/7937#pullrequestreview-3029859465 # Rationale for this change Using word-level (u64) bit scanning And use Brian Kernighan’s algorithm, details comments: // Iterate over each set bit in `z` (null mask) using a bit-parallel // approach (Brian Kernighan’s algorithm): // - `z.trailing_zeros()` finds the index of the least-significant 1-bit, // which corresponds to a null element’s position relative to `base`. // - Writing `(base + tz)` records the absolute index of this null. // - `z &= z - 1` clears that lowest set bit, so on next iteration we // process the next null bit without scanning through all bits one-by-one. // This method avoids per-bit branching and runs in O(k) time for k nulls, // making it much faster than checking every position, especially when nulls are sparse. # What changes are included in this PR? There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR. # Are these changes tested? We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? # Are there any user-facing changes? If there are user-facing changes then we may require documentation to be updated before approving the PR. If there are any breaking changes to public APIs, please call them out. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
