Hi Rebecca, Thanks for the patch, it looks good. I find that even with your patch the builtin_tgamma still fails. It turns out to be the issue of the test case. So I send a patch "[PATCH] utests: fix test case builtin_tgamma." to fix it.
Thanks! Ruiling > -----Original Message----- > From: Beignet [mailto:beignet-boun...@lists.freedesktop.org] On Behalf Of > Rebecca N. Palmer > Sent: Friday, April 17, 2015 8:48 PM > To: beignet@lists.freedesktop.org > Subject: [Beignet] [PATCH] Make tgamma meet the accuracy standard > > The old tgamma=exp(lgamma) implementation had high rounding error on > large outputs, exceeding the 16ulp specification for approx. x>8 (hence the > test failure in strict conformance mode). > > Replace this with an implementation based on glibc's > http://sources.debian.net/src/glibc/2.19-17/sysdeps/ieee754/flt-32/e_gam > maf_r.c/ > > Signed-off-by: Rebecca Palmer <rebecca_pal...@zoho.com> > > diff --git a/backend/src/libocl/tmpl/ocl_math.tmpl.cl > b/backend/src/libocl/tmpl/ocl_math.tmpl.cl > index da5b9a9..49edd95 100644 > --- a/backend/src/libocl/tmpl/ocl_math.tmpl.cl > +++ b/backend/src/libocl/tmpl/ocl_math.tmpl.cl > @@ -1744,12 +1744,6 @@ OVERLOADABLE float > __gen_ocl_internal_exp(float x) { > } > } > > -INLINE_OVERLOADABLE float tgamma(float x) { > - float y; > - int s; > - y=lgamma_r(x,&s); > - return __gen_ocl_internal_exp(y)*s; > -} > > /* erf,erfc from glibc s_erff.c -- float version of s_erf.c. > * Conversion to float by Ian Lance Taylor, Cygnus Support, > i...@cygnus.com. > @@ -3165,6 +3159,95 @@ float __gen_ocl_internal_pown(float x, int y) { > return sn*z; > } > > +OVERLOADABLE float tgamma (float x) > +{ > + /* based on glibc __ieee754_gammaf_r by Ulrich Drepper > +<drep...@cygnus.com> */ > + > + unsigned int hx; > + GEN_OCL_GET_FLOAT_WORD(hx,x); > + if (hx == 0xff800000) > + { > + /* x == -Inf. According to ISO this is NaN. */ > + return NAN; > + } > + if ((hx & 0x7f800000) == 0x7f800000) > + { > + /* Positive infinity (return positive infinity) or NaN (return > + NaN). */ > + return x; > + } > + if (x < 0.0f && __gen_ocl_internal_floor (x) == x) > + { > + /* integer x < 0 */ > + return NAN; > + } > + > + if (x >= 36.0f) > + { > + /* Overflow. */ > + return INFINITY; > + } > + else if (x <= 0.0f && x >= -FLT_EPSILON / 4.0f) > + { > + return 1.0f / x; > + } > + else > + { > + float sinpix = __gen_ocl_internal_sinpi(x); > + if (x <= -42.0f) > + /* Underflow. */ > + {return 0.0f * sinpix /*for sign*/;} > + int exp2_adj = 0; > + float x_abs = __gen_ocl_fabs(x); > + float gam0; > + > + if (x_abs < 4.0f) { > + /* gamma = exp(lgamma) is only accurate for small lgamma */ > + float prod,x_adj; > + if (x_abs < 0.5f) { > + prod = 1.0f / x_abs; > + x_adj = x_abs + 1.0f; > + } else if (x_abs <= 1.5f) { > + prod = 1.0f; > + x_adj = x_abs; > + } else if (x_abs < 2.5f) { > + x_adj = x_abs - 1.0f; > + prod = x_adj; > + } else { > + x_adj = x_abs - 2.0f; > + prod = x_adj * (x_abs - 1.0f); > + } > + gam0 = __gen_ocl_internal_exp (lgamma (x_adj)) * prod; > + } > + else { > + /* Compute gamma (X) using Stirling's approximation, > + starting by computing pow (X, X) with a power of 2 > + factored out to avoid intermediate overflow. */ > + float x_int = __gen_ocl_internal_round (x_abs); > + float x_frac = x_abs - x_int; > + int x_log2; > + float x_mant = frexp (x_abs, &x_log2); > + if (x_mant < M_SQRT1_2_F) > + { > + x_log2--; > + x_mant *= 2.0f; > + } > + exp2_adj = x_log2 * (int) x_int; > + float ret = (__gen_ocl_internal_pow(x_mant, x_abs) > + * exp2 (x_log2 * x_frac) > + * __gen_ocl_internal_exp (-x_abs) > + * sqrt (2.0f * M_PI_F / x_abs) ); > + > + float x2 = x_abs * x_abs; > + float bsum = (0x3.403404p-12f / x2 -0xb.60b61p-12f) / x2 + > 0x1.555556p-4f; > + gam0 = ret + ret * __gen_ocl_internal_expm1 (bsum / x_abs); > + } > + if (x > 0.0f) {return __gen_ocl_internal_ldexp (gam0, exp2_adj);} > + float gam1 = M_PI_F / (-x * sinpix * gam0); > + return __gen_ocl_internal_ldexp (gam1, -exp2_adj); > + } > +} > + > OVERLOADABLE float hypot(float x, float y) { > if (__ocl_math_fastpath_flag) > return __gen_ocl_internal_fastpath_hypot(x, y); > > _______________________________________________ > Beignet mailing list > Beignet@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/beignet _______________________________________________ Beignet mailing list Beignet@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/beignet
