Permalink
Browse files

libm: fix tgamma to actually do return true gamma function

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
  • Loading branch information...
1 parent 7e30860 commit 8b34cac8748067dbebc99f1b8450c5de91661db5 Denys Vlasenko committed Oct 31, 2010
Showing with 106 additions and 26 deletions.
  1. +23 −19 libm/e_lgamma_r.c
  2. +1 −0 test/math/Makefile.in
  3. +0 −1 test/math/c99_test.c
  4. +73 −0 test/math/gamma.c
  5. +1 −0 test/math/ilogb.c
  6. +7 −6 test/math/rint.c
  7. +1 −0 test/math/signgam.c
View
42 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)
View
1 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
View
1 test/math/c99_test.c
@@ -1,4 +1,3 @@
-//#define _GNU_SOURCE 1
#include <math.h>
#include <float.h>
#include <stdlib.h>
View
73 test/math/gamma.c
@@ -0,0 +1,73 @@
+#include <math.h>
+#include <float.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#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;
+}
View
1 test/math/ilogb.c
@@ -1,4 +1,5 @@
#include <math.h>
+#include <float.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
View
13 test/math/rint.c
@@ -1,17 +1,18 @@
#include <math.h>
+#include <float.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#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;
}
View
1 test/math/signgam.c
@@ -1,5 +1,6 @@
#define _XOPEN_SOURCE 600
#include <math.h>
+#include <float.h>
#include <stdio.h>
double zero = 0.0;

0 comments on commit 8b34cac

Please sign in to comment.