From 8b34cac8748067dbebc99f1b8450c5de91661db5 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Sun, 31 Oct 2010 04:36:02 +0100 Subject: libm: fix tgamma to actually do return true gamma function Signed-off-by: Denys Vlasenko --- libm/e_lgamma_r.c | 42 +++++++++++++++-------------- test/math/Makefile.in | 1 + test/math/c99_test.c | 1 - test/math/gamma.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++ test/math/ilogb.c | 1 + test/math/rint.c | 13 ++++----- test/math/signgam.c | 1 + 7 files changed, 106 insertions(+), 26 deletions(-) create mode 100644 test/math/gamma.c diff --git a/libm/e_lgamma_r.c b/libm/e_lgamma_r.c index 6d5d9c514..dbb0a0d5d 100644 --- a/libm/e_lgamma_r.c +++ b/libm/e_lgamma_r.c @@ -360,31 +360,35 @@ strong_alias(__ieee754_lgamma, gamma) #endif -/* FIXME! Looks like someone just used __ieee754_gamma_r, - * believing it's a "true" gamma function, but it was not! - * Our tgamma is WRONG. - */ - /* double tgamma(double x) * Return the Gamma function of x. */ double tgamma(double x) { - double y; - int local_signgam; + int sign_of_gamma; + int32_t hx; + u_int32_t lx; - y = __ieee754_lgamma_r(x, &local_signgam); // was __ieee754_gamma_r - if (local_signgam < 0) - y = -y; -#ifndef _IEEE_LIBM - if (_LIB_VERSION == _IEEE_) - return y; - if (!isfinite(y) && isfinite(x)) { - if (floor(x) == x && x <= 0.0) - return __kernel_standard(x, x, 41); /* tgamma pole */ - return __kernel_standard(x, x, 40); /* tgamma overflow */ + /* We don't have a real gamma implementation now. We'll use lgamma + and the exp function. But due to the required boundary + conditions we must check some values separately. */ + + EXTRACT_WORDS(hx, lx, x); + + if (((hx & 0x7fffffff) | lx) == 0) { + /* Return value for x == 0 is Inf with divide by zero exception. */ + return 1.0 / x; } -#endif - return y; + if (hx < 0 && (u_int32_t)hx < 0xfff00000 && rint(x) == x) { + /* Return value for integer x < 0 is NaN with invalid exception. */ + return (x - x) / (x - x); + } + if ((u_int32_t)hx == 0xfff00000 && lx == 0) { + /* x == -Inf. According to ISO this is NaN. */ + return x - x; + } + + x = exp(lgamma_r(x, &sign_of_gamma)); + return sign_of_gamma >= 0 ? x : -x; } libm_hidden_def(tgamma) diff --git a/test/math/Makefile.in b/test/math/Makefile.in index 3f9edf833..e76cbdbaa 100644 --- a/test/math/Makefile.in +++ b/test/math/Makefile.in @@ -3,6 +3,7 @@ TESTS := basic-test tst-definitions test-fpucw test-float test-ifloat test-double test-idouble \ rint signgam ilogb +# gamma (removed from TESTS, need to add "small errors are ok" machinery there) ifeq ($(UCLIBC_HAS_LONG_DOUBLE_MATH),y) TESTS += test-ldouble test-ildoubl compile_test c99_test else diff --git a/test/math/c99_test.c b/test/math/c99_test.c index fd6feeafc..73382e41b 100644 --- a/test/math/c99_test.c +++ b/test/math/c99_test.c @@ -1,4 +1,3 @@ -//#define _GNU_SOURCE 1 #include #include #include diff --git a/test/math/gamma.c b/test/math/gamma.c new file mode 100644 index 000000000..69c10afa4 --- /dev/null +++ b/test/math/gamma.c @@ -0,0 +1,73 @@ +#include +#include +#include +#include +#include + +#define check_d1(func, param, expected) \ +do { \ + int err; hex_union ur; hex_union up; \ + double result = func(param); up.f = param; ur.f = result; \ + errors += (err = (result != (expected))); \ + err \ + ? printf("FAIL: %s(%g/"HEXFMT")=%g/"HEXFMT" (expected %g)\n", \ + #func, (double)(param), (long long)up.hex, result, (long long)ur.hex, (double)(expected)) \ + : printf("PASS: %s(%g)=%g\n", #func, (double)(param), result); \ +} while (0) + +#define HEXFMT "%08llx" +typedef union { + double f; + uint64_t hex; +} hex_union; +double result; + +#define M_2_SQRT_PIl 3.5449077018110320545963349666822903L /* 2 sqrt (M_PIl) */ +#define M_SQRT_PIl 1.7724538509055160272981674833411451L /* sqrt (M_PIl) */ + +double zero = 0.0; +double minus_zero = 0.0; +double nan_value = 0.0; +int errors = 0; + +int main(void) +{ + nan_value /= nan_value; + minus_zero = copysign(zero, -1.0); + + //check_d1(tgamma, HUGE_VAL, NAN); + //check_d1(tgamma, negative_integer, NAN); + check_d1(tgamma, 0.0, HUGE_VAL); /* pole */ + check_d1(tgamma, minus_zero, -HUGE_VAL); /* pole */ + check_d1(tgamma, DBL_MAX/2, HUGE_VAL); /* overflow to inf */ + check_d1(tgamma, DBL_MAX, HUGE_VAL); /* overflow to inf */ + check_d1(tgamma, HUGE_VAL, HUGE_VAL); /* overflow to inf */ + check_d1(tgamma, 7, 2*3*4*5*6); /* normal value */ + check_d1(tgamma, -0.5, -M_2_SQRT_PIl); /* normal value (testing negative points) */ + + check_d1(lgamma, -HUGE_VAL, HUGE_VAL); + //check_d1(lgamma, HUGE_VAL, NAN); + check_d1(lgamma, 0.0, HUGE_VAL); /* pole */ + check_d1(lgamma, minus_zero, HUGE_VAL); /* pole */ + check_d1(lgamma, 1.0, 0.0); + check_d1(lgamma, 2.0, 0.0); + check_d1(lgamma, DBL_MAX/2, HUGE_VAL); /* overflow to inf */ + check_d1(lgamma, DBL_MAX, HUGE_VAL); /* overflow to inf */ + check_d1(lgamma, HUGE_VAL, HUGE_VAL); /* overflow to inf */ + check_d1(lgamma, 7, log(2*3*4*5*6)); /* normal value */ + + /* In glibc, gamma == lgamma. (In BSD, it's == tgamma */ + check_d1(gamma, -HUGE_VAL, HUGE_VAL); + //check_d1(gamma, HUGE_VAL, NAN); + check_d1(gamma, 0.0, HUGE_VAL); /* pole */ + check_d1(gamma, minus_zero, HUGE_VAL); /* pole */ + check_d1(gamma, 1.0, 0.0); + check_d1(gamma, 2.0, 0.0); + check_d1(gamma, DBL_MAX/2, HUGE_VAL); /* overflow to inf */ + check_d1(gamma, DBL_MAX, HUGE_VAL); /* overflow to inf */ + check_d1(gamma, HUGE_VAL, HUGE_VAL); /* overflow to inf */ + check_d1(gamma, 7, log(2*3*4*5*6)); /* normal value */ + + printf("Errors: %d\n", errors); + return errors; +} diff --git a/test/math/ilogb.c b/test/math/ilogb.c index e439f8c37..041e66b0e 100644 --- a/test/math/ilogb.c +++ b/test/math/ilogb.c @@ -1,4 +1,5 @@ #include +#include #include #include #include diff --git a/test/math/rint.c b/test/math/rint.c index c7bfab920..b595459a3 100644 --- a/test/math/rint.c +++ b/test/math/rint.c @@ -1,4 +1,5 @@ #include +#include #include #include #include @@ -6,12 +7,12 @@ #define check_d1(func, param, expected) \ do { \ int err; hex_union ur; hex_union up; \ - up.f = param; ur.f = result = func(param); \ - errors += (err = (result != expected)); \ + double result = func(param); up.f = param; ur.f = result; \ + errors += (err = (result != (expected))); \ err \ ? printf("FAIL: %s(%g/"HEXFMT")=%g/"HEXFMT" (expected %g)\n", \ - #func, (param), (long long)up.hex, result, (long long)ur.hex, expected) \ - : printf("PASS: %s(%g)=%g\n", #func, (param), result); \ + #func, (double)(param), (long long)up.hex, result, (long long)ur.hex, (double)(expected)) \ + : printf("PASS: %s(%g)=%g\n", #func, (double)(param), result); \ } while (0) #define HEXFMT "%08llx" @@ -27,6 +28,6 @@ int main(void) { check_d1(rint, 0.6, 1.0); - printf("Errors: %d\n", errors); - return errors; + printf("Errors: %d\n", errors); + return errors; } diff --git a/test/math/signgam.c b/test/math/signgam.c index d79d6afb2..2f1adbaad 100644 --- a/test/math/signgam.c +++ b/test/math/signgam.c @@ -1,5 +1,6 @@ #define _XOPEN_SOURCE 600 #include +#include #include double zero = 0.0; -- cgit v1.2.3