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author | Wilco Dijkstra <Wilco.Dijkstra@arm.com> | 2021-03-08 17:07:39 -0300 |
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committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-12-13 09:02:34 -0300 |
commit | 6c848d70383e1dbe932ef41723ac0abfdeec7ca8 (patch) | |
tree | 366dd2d23fb72a4a31b7e44a81d355f46627355a /libio/bug-memstream1.c | |
parent | 7fe0ace3e289c88cab5014cef94e946fd695221f (diff) | |
download | glibc-6c848d70383e1dbe932ef41723ac0abfdeec7ca8.tar.gz glibc-6c848d70383e1dbe932ef41723ac0abfdeec7ca8.tar.xz glibc-6c848d70383e1dbe932ef41723ac0abfdeec7ca8.zip |
math: Use an improved algorithm for hypot (dbl-64)
This implementation is based on the 'An Improved Algorithm for hypot(a,b)' by Carlos F. Borges [1] using the MyHypot3 with the following changes: - Handle qNaN and sNaN. - Tune the 'widely varying operands' to avoid spurious underflow due the multiplication and fix the return value for upwards rounding mode. - Handle required underflow exception for denormal results. The main advantage of the new algorithm is its precision: with a random 1e9 input pairs in the range of [DBL_MIN, DBL_MAX], glibc current implementation shows around 0.34% results with an error of 1 ulp (3424869 results) while the new implementation only shows 0.002% of total (18851). The performance result are also only slight worse than current implementation. On x86_64 (Ryzen 5900X) with gcc 12: Before: "hypot": { "workload-random": { "duration": 3.73319e+09, "iterations": 1.12e+08, "reciprocal-throughput": 22.8737, "latency": 43.7904, "max-throughput": 4.37184e+07, "min-throughput": 2.28361e+07 } } After: "hypot": { "workload-random": { "duration": 3.7597e+09, "iterations": 9.8e+07, "reciprocal-throughput": 23.7547, "latency": 52.9739, "max-throughput": 4.2097e+07, "min-throughput": 1.88772e+07 } } Co-Authored-By: Adhemerval Zanella <adhemerval.zanella@linaro.org> Checked on x86_64-linux-gnu and aarch64-linux-gnu. [1] https://arxiv.org/pdf/1904.09481.pdf
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