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| author | Szabolcs Nagy <nsz@port70.net> | 2014-10-29 00:34:37 +0100 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2014-10-31 11:35:40 -0400 |
| commit | 0ce946cf808274c2d6e5419b139e130c8ad4bd30 (patch) | |
| tree | e6614e756dde0afbcd48e38916d0208fed93ece1 /src/math/__rem_pio2l.c | |
| parent | 79ca86094d70f43252b683c3a3ccb572d462cf28 (diff) | |
| download | musl-0ce946cf808274c2d6e5419b139e130c8ad4bd30.tar.gz musl-0ce946cf808274c2d6e5419b139e130c8ad4bd30.tar.bz2 musl-0ce946cf808274c2d6e5419b139e130c8ad4bd30.tar.xz musl-0ce946cf808274c2d6e5419b139e130c8ad4bd30.zip | |
math: use the rounding idiom consistently
the idiomatic rounding of x is
n = x + toint - toint;
where toint is either 1/EPSILON (x is non-negative) or 1.5/EPSILON
(x may be negative and nearest rounding mode is assumed) and EPSILON is
according to the evaluation precision (the type of toint is not very
important, because single precision float can represent the 1/EPSILON of
ieee binary128).
in case of FLT_EVAL_METHOD!=0 this avoids a useless store to double or
float precision, and the long double code became cleaner with
1/LDBL_EPSILON instead of ifdefs for toint.
__rem_pio2f and __rem_pio2 functions slightly changed semantics:
on i386 a double-rounding is avoided so close to half-way cases may
get evaluated differently eg. as sin(pi/4-eps) instead of cos(pi/4+eps)
Diffstat (limited to 'src/math/__rem_pio2l.c')
| -rw-r--r-- | src/math/__rem_pio2l.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/src/math/__rem_pio2l.c b/src/math/__rem_pio2l.c index 8b15b7b2..77255bd8 100644 --- a/src/math/__rem_pio2l.c +++ b/src/math/__rem_pio2l.c @@ -20,10 +20,11 @@ * use __rem_pio2_large() for large x */ +static const long double toint = 1.5/LDBL_EPSILON; + #if LDBL_MANT_DIG == 64 /* u ~< 0x1p25*pi/2 */ #define SMALL(u) (((u.i.se & 0x7fffU)<<16 | u.i.m>>48) < ((0x3fff + 25)<<16 | 0x921f>>1 | 0x8000)) -#define TOINT 0x1.8p63 #define QUOBITS(x) ((uint32_t)(int32_t)x & 0x7fffffff) #define ROUND1 22 #define ROUND2 61 @@ -50,7 +51,6 @@ pio2_3t = -2.75299651904407171810e-37L; /* -0xbb5bf6c7ddd660ce.0p-185 */ #elif LDBL_MANT_DIG == 113 /* u ~< 0x1p45*pi/2 */ #define SMALL(u) (((u.i.se & 0x7fffU)<<16 | u.i.top) < ((0x3fff + 45)<<16 | 0x921f)) -#define TOINT 0x1.8p112 #define QUOBITS(x) ((uint32_t)(int64_t)x & 0x7fffffff) #define ROUND1 51 #define ROUND2 119 @@ -77,7 +77,7 @@ int __rem_pio2l(long double x, long double *y) ex = u.i.se & 0x7fff; if (SMALL(u)) { /* rint(x/(pi/2)), Assume round-to-nearest. */ - fn = x*invpio2 + TOINT - TOINT; + fn = x*invpio2 + toint - toint; n = QUOBITS(fn); r = x-fn*pio2_1; w = fn*pio2_1t; /* 1st round good to 102/180 bits (ld80/ld128) */ |