svn commit: r268588 - head/lib/msun/src
Steve Kargl
kargl at FreeBSD.org
Sun Jul 13 15:45:47 UTC 2014
Author: kargl
Date: Sun Jul 13 15:45:45 2014
New Revision: 268588
URL: http://svnweb.freebsd.org/changeset/base/268588
Log:
* Use the volatile qualifier for 'tiny' to prevent compilers
from erronously constant folding expressions of the form
'1 - tiny'. This allows erf[f](x) to raise INEXACT.
* Use 0.5, 1, and 2, which are exactly representable in radix-2
floating point formats. This reduces diffs between s_erf[fl].c.
* While here, add a comment about efx and efx8.
Modified:
head/lib/msun/src/s_erf.c
head/lib/msun/src/s_erff.c
Modified: head/lib/msun/src/s_erf.c
==============================================================================
--- head/lib/msun/src/s_erf.c Sun Jul 13 15:15:51 2014 (r268587)
+++ head/lib/msun/src/s_erf.c Sun Jul 13 15:45:45 2014 (r268588)
@@ -111,13 +111,20 @@ __FBSDID("$FreeBSD$");
#include "math.h"
#include "math_private.h"
+/* XXX Prevent compilers from erroneously constant folding: */
+static const volatile double tiny= 1e-300;
+
static const double
-tiny = 1e-300,
-half= 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */
-one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
-two = 2.00000000000000000000e+00, /* 0x40000000, 0x00000000 */
+half= 0.5,
+one = 1,
+two = 2,
/* c = (float)0.84506291151 */
erx = 8.45062911510467529297e-01, /* 0x3FEB0AC1, 0x60000000 */
+/*
+ * In the domain [0, 2**-28], only the first term in the power series
+ * expansion of erf(x) is used. The magnitude of the first neglected
+ * terms is less than 2**-84.
+ */
efx = 1.28379167095512586316e-01, /* 0x3FC06EBA, 0x8214DB69 */
efx8= 1.02703333676410069053e+00, /* 0x3FF06EBA, 0x8214DB69 */
/*
Modified: head/lib/msun/src/s_erff.c
==============================================================================
--- head/lib/msun/src/s_erff.c Sun Jul 13 15:15:51 2014 (r268587)
+++ head/lib/msun/src/s_erff.c Sun Jul 13 15:45:45 2014 (r268588)
@@ -19,13 +19,18 @@ __FBSDID("$FreeBSD$");
#include "math.h"
#include "math_private.h"
+/* XXX Prevent compilers from erroneously constant folding: */
+static const volatile float tiny = 1e-30;
+
static const float
-tiny = 1e-30,
-half= 5.0000000000e-01, /* 0x3F000000 */
-one = 1.0000000000e+00, /* 0x3F800000 */
-two = 2.0000000000e+00, /* 0x40000000 */
+half= 0.5,
+one = 1,
+two = 2,
+erx = 8.42697144e-01, /* 0x3f57bb00 */
/*
- * Coefficients for approximation to erf on [0,0.84375]
+ * In the domain [0, 2**-14], only the first term in the power series
+ * expansion of erf(x) is used. The magnitude of the first neglected
+ * terms is less than 2**-42.
*/
efx = 1.2837916613e-01, /* 0x3e0375d4 */
efx8= 1.0270333290e+00, /* 0x3f8375d4 */
@@ -43,7 +48,6 @@ qq3 = -1.98859419e-03F, /* -0x1.04a626p
* Domain [0.84375, 1.25], range ~[-1.953e-11,1.940e-11]:
* |(erf(x) - erx) - p(x)/q(x)| < 2**-36.
*/
-erx = 8.42697144e-01F, /* 0x1.af7600p-1. erf(1) rounded to 16 bits. */
pa0 = 3.64939137e-06F, /* 0x1.e9d022p-19 */
pa1 = 4.15109694e-01F, /* 0x1.a91284p-2 */
pa2 = -1.65179938e-01F, /* -0x1.5249dcp-3 */
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