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* math: lgamma cleanup (simpler sin(pi*x) for the negative case)Szabolcs Nagy2013-11-211-20/+20
| | | | | | | | | * simplify sin_pi(x) (don't care about inexact here, the result is inexact anyway, and x is not so small to underflow) * in lgammal add the previously removed special case for x==1 and x==2 (to fix the sign of zero in downward rounding mode) * only define lgammal on supported long double platforms * change tgamma so the generated code is a bit smaller
* math: fix tgamma to raise underflow for large negative valuesSzabolcs Nagy2013-08-151-0/+1
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* math: use double_t for temporaries to avoid stores on i386Szabolcs Nagy2013-05-151-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When FLT_EVAL_METHOD!=0 (only i386 with x87 fp) the excess precision of an expression must be removed in an assignment. (gcc needs -fexcess-precision=standard or -std=c99 for this) This is done by extra load/store instructions which adds code bloat when lot of temporaries are used and it makes the result less precise in many cases. Using double_t and float_t avoids these issues on i386 and it makes no difference on other archs. For now only a few functions are modified where the excess precision is clearly beneficial (mostly polynomial evaluations with temporaries). object size differences on i386, gcc-4.8: old new __cosdf.o 123 95 __cos.o 199 169 __sindf.o 131 95 __sin.o 225 203 __tandf.o 207 151 __tan.o 605 499 erff.o 1470 1416 erf.o 1703 1649 j0f.o 1779 1745 j0.o 2308 2274 j1f.o 1602 1568 j1.o 2286 2252 tgamma.o 1431 1424 math/*.o 64164 63635
* math: add a non-dummy tgamma implementationSzabolcs Nagy2012-12-121-9/+214
| | | | | | | | | | | | uses the lanczos approximation method with the usual tweaks. same parameters were selected as in boost and python. (avoides some extra work and special casing found in boost so the precision is not that good: measured error is <5ulp for positive x and <10ulp for negative) an alternative lgamma_r implementation is also given in the same file which is simpler and smaller than the current one, but less precise so it's ifdefed out for now.
* math: add dummy tgamma and tgammaf implementationsnsz2012-03-271-0/+16