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| author | Wilco Dijkstra <wdijkstr@arm.com> | 2018-02-12 10:42:42 +0000 |
|---|---|---|
| committer | Wilco Dijkstra <wdijkstr@arm.com> | 2018-02-12 10:47:09 +0000 |
| commit | c3d466cba1692708a19c6ff829d0386c83a0c6e5 (patch) | |
| tree | d01ce6103dc25d3b662898c3429b8b103b8d3155 /benchtests | |
| parent | 7bb087bd7bfe3616c4c0974a3f7352b593353ea5 (diff) | |
| download | glibc-c3d466cba1692708a19c6ff829d0386c83a0c6e5.zip glibc-c3d466cba1692708a19c6ff829d0386c83a0c6e5.tar.gz glibc-c3d466cba1692708a19c6ff829d0386c83a0c6e5.tar.bz2 | |
Remove slow paths from pow
Remove the slow paths from pow. Like several other double precision math
functions, pow is exactly rounded. This is not required from math functions
and causes major overheads as it requires multiple fallbacks using higher
precision arithmetic if a result is close to 0.5ULP. Ridiculous slowdowns
of up to 100000x have been reported when the highest precision path triggers.
All GLIBC math tests pass on AArch64 and x64 (with ULP of pow set to 1).
The worst case error is ~0.506ULP. A simple test over a few hundred million
values shows pow is 10% faster on average. This fixes BZ #13932.
[BZ #13932]
* sysdeps/ieee754/dbl-64/uexp.h (err_1): Remove.
* benchtests/pow-inputs: Update comment for slow path cases.
* manual/probes.texi (slowpow_p10): Delete removed probe.
(slowpow_p10): Likewise.
* math/Makefile: Remove halfulp.c and slowpow.c.
* sysdeps/aarch64/libm-test-ulps: Set ULP of pow to 1.
* sysdeps/generic/math_private.h (__exp1): Remove error argument.
(__halfulp): Remove.
(__slowpow): Remove.
* sysdeps/i386/fpu/halfulp.c: Delete file.
* sysdeps/i386/fpu/slowpow.c: Likewise.
* sysdeps/ia64/fpu/halfulp.c: Likewise.
* sysdeps/ia64/fpu/slowpow.c: Likewise.
* sysdeps/ieee754/dbl-64/e_exp.c (__exp1): Remove error argument,
improve comments and add error analysis.
* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Add error analysis.
(power1): Remove function:
(log1): Remove error argument, add error analysis.
(my_log2): Remove function.
* sysdeps/ieee754/dbl-64/halfulp.c: Delete file.
* sysdeps/ieee754/dbl-64/slowpow.c: Likewise.
* sysdeps/m68k/m680x0/fpu/halfulp.c: Likewise.
* sysdeps/m68k/m680x0/fpu/slowpow.c: Likewise.
* sysdeps/powerpc/power4/fpu/Makefile: Remove CPPFLAGS-slowpow.c.
* sysdeps/x86_64/fpu/libm-test-ulps: Set ULP of pow to 1.
* sysdeps/x86_64/fpu/multiarch/Makefile: Remove slowpow-fma.c,
slowpow-fma4.c, halfulp-fma.c, halfulp-fma4.c.
* sysdeps/x86_64/fpu/multiarch/e_pow-fma.c (__slowpow): Remove define.
* sysdeps/x86_64/fpu/multiarch/e_pow-fma4.c (__slowpow): Likewise.
* sysdeps/x86_64/fpu/multiarch/halfulp-fma.c: Delete file.
* sysdeps/x86_64/fpu/multiarch/halfulp-fma4.c: Likewise.
* sysdeps/x86_64/fpu/multiarch/slowpow-fma.c: Likewise.
* sysdeps/x86_64/fpu/multiarch/slowpow-fma4.c: Likewise.
Diffstat (limited to 'benchtests')
| -rw-r--r-- | benchtests/pow-inputs | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/benchtests/pow-inputs b/benchtests/pow-inputs index 78f8ac7..4a51aac 100644 --- a/benchtests/pow-inputs +++ b/benchtests/pow-inputs @@ -302,8 +302,7 @@ 0x1.c004d2256a5b8p402, -0x1.a01df480fdcb7p98 0x1.52b9d41aaa1e9p-589, -0x1.292cb15f1459dp46 -0x1.ea9ca6fa0919ep-279, -0x1.601e44b6a588cp40 -# pow slow path at 240 bits -# Implemented in sysdeps/ieee754/dbl-64/slowpow.c +# old pow slow path at 240 bits ## name: 240bits 0x1.01fcd33493ea3p596, -0x1.724bd4e887783p-14 0x1.032ff59ab34fdp-540, -0x1.61e3632080b87p-24 @@ -405,8 +404,7 @@ 0x1.fae913d4f952ep-809, -0x1.4b649402fce63p-6 0x1.fe6d725408f24p484, -0x1.25f4f6441d2e4p-12 0x1.ff6393f9150ccp-718, 0x1.a0cb50a9bf2f3p-31 -# pow slowest path at 768 bits -# Implemented in sysdeps/ieee754/dbl-64/slowpow.c +# old pow slowest path at 768 bits ## name: 768bits 1.0000000000000020, 1.5 0x1.006777b4b61dep843, -0x1.67e3145491872p-1 |