[libc-commits] [PATCH] D115408: [libc] Implement correctly rounded logf based on RLIBM library.

Santosh Nagarakatte via Phabricator via libc-commits libc-commits at lists.llvm.org
Fri Dec 10 15:41:45 PST 2021

santoshn added a comment.

One reason there are 21 exceptional inputs is because this patch uses a different polynomial evaluation than Horner's method that RLIBM uses. Let me generate a new polynomial using the polynomial evaluation in the patch. It will have significantly fewer exceptional inputs for a 5th-degree polynomial for log.

Addressing Paul Zimmerman's comment about other rounding modes, if you use the RLIBM polynomial generated with the round-to-odd for a 34-bit FP, it will produce correct results for all rounding modes. Isn't that a better solution than using the round-to-nearest polynomial and then tweaking it with exceptional inputs?

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