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authorCarlos O'Donell <carlos@redhat.com>2013-06-03 14:49:48 -0400
committerCarlos O'Donell <carlos@redhat.com>2013-06-03 14:49:48 -0400
commit8b0ccb2d7fd1ec646a622a16bd64e356739ffca3 (patch)
treeb7500d0f98c33e9fa91366fc95ef456eff692d15 /math
parent3b3c4d40c18e0e340c68a02487014d0001211382 (diff)
downloadglibc-8b0ccb2d7fd1ec646a622a16bd64e356739ffca3.tar.gz
BZ #15536: Fix ulp for 128-bit IBM long double.
In 128-bit IBM long double the precision of the type decreases as you approach subnormal numbers, equaling that of a double for subnormal numbers. Therefore adjust the computation in ulp to use 2^(MIN_EXP - MANT_DIG) which is correct for FP_SUBNORMAL for all types.
Diffstat (limited to 'math')
-rw-r--r--math/libm-test.inc37
1 files changed, 26 insertions, 11 deletions
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 7a6bf09a66..6870d96d5b 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -269,8 +269,8 @@ static FLOAT max_error, real_max_error, imag_max_error;
#define MANT_DIG CHOOSE ((LDBL_MANT_DIG-1), (DBL_MANT_DIG-1), (FLT_MANT_DIG-1), \
(LDBL_MANT_DIG-1), (DBL_MANT_DIG-1), (FLT_MANT_DIG-1))
-#define MAX_EXP CHOOSE ((LDBL_MAX_EXP-1), (DBL_MAX_EXP-1), (FLT_MAX_EXP-1), \
- (LDBL_MAX_EXP-1), (DBL_MAX_EXP-1), (FLT_MAX_EXP-1))
+#define MIN_EXP CHOOSE ((LDBL_MIN_EXP-1), (DBL_MIN_EXP-1), (FLT_MIN_EXP-1), \
+ (LDBL_MIN_EXP-1), (DBL_MIN_EXP-1), (FLT_MIN_EXP-1))
/* Compare KEY (a string, with the name of a test or a function) with
ULP (a pointer to a struct ulp_data structure), returning a value
@@ -680,7 +680,7 @@ ulp (FLOAT value)
/* Fall through... */
case FP_SUBNORMAL:
/* The next closest subnormal value is a constant distance away. */
- ulp = FUNC(ldexp) (1.0, 1 - (MAX_EXP + MANT_DIG));
+ ulp = FUNC(ldexp) (1.0, MIN_EXP - MANT_DIG);
break;
case FP_NORMAL:
@@ -14583,7 +14583,7 @@ parse_opt (int key, char *arg, struct argp_state *state)
void
check_ulp (void)
{
- FLOAT ulps, value;
+ FLOAT ulps, ulpx, value;
int i;
/* Check ulp of zero is a subnormal value... */
ulps = ulp (0x0.0p0);
@@ -14599,30 +14599,45 @@ check_ulp (void)
fprintf (stderr, "ulp (1.0L) is not FP_NORMAL\n");
exit (EXIT_FAILURE);
}
+
+ /* Compute the next subnormal value using nextafter to validate ulp.
+ We allow +/- 1 ulp around the represented value. */
+ value = FUNC(nextafter) (0, 1);
+ ulps = ULPDIFF (value, 0);
+ ulpx = ulp (1.0L);
+ if (ulps < (1.0L - ulpx) || ulps > (1.0L + ulpx))
+ {
+ fprintf (stderr, "Value outside of 1 +/- 1ulp.\n");
+ exit (EXIT_FAILURE);
+ }
/* Compute the nearest representable number from 10 towards 20.
- The result is 10 + 1ulp. We use this to check the ulp function. */
+ The result is 10 + 1ulp. We use this to check the ulp function.
+ We allow +/- 1 ulp around the represented value. */
value = FUNC(nextafter) (10, 20);
ulps = ULPDIFF (value, 10);
- if (ulps > 1.0L)
+ ulpx = ulp (1.0L);
+ if (ulps < (1.0L - ulpx) || ulps > (1.0L + ulpx))
{
- fprintf (stderr, "The value of ulp (10+1ulp,10) is greater than 1 ulp.\n");
+ fprintf (stderr, "Value outside of 1 +/- 1ulp.\n");
exit (EXIT_FAILURE);
}
/* This gives one more ulp. */
value = FUNC(nextafter) (value, 20);
ulps = ULPDIFF (value, 10);
- if (ulps > 2.0L)
+ ulpx = ulp (2.0L);
+ if (ulps < (2.0L - ulpx) || ulps > (2.0L + ulpx))
{
- fprintf (stderr, "The value of ulp (10+2ulp,10) is greater than 2 ulp.\n");
+ fprintf (stderr, "Value outside of 2 +/- 1ulp.\n");
exit (EXIT_FAILURE);
}
/* And now calculate 100 ulp. */
for (i = 2; i < 100; i++)
value = FUNC(nextafter) (value, 20);
ulps = ULPDIFF (value, 10);
- if (ulps > 100.0L)
+ ulpx = ulp (100.0L);
+ if (ulps < (100.0L - ulpx) || ulps > (100.0L + ulpx))
{
- fprintf (stderr, "The value of ulp (10+100ulp,10) is greater than 100 ulp.\n");
+ fprintf (stderr, "Value outside of 100 +/- 1ulp.\n");
exit (EXIT_FAILURE);
}
}