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authorSzabolcs Nagy <nsz@port70.net>2013-09-05 16:57:46 +0000
committerSzabolcs Nagy <nsz@port70.net>2013-09-05 16:57:46 +0000
commitf4d9bfb3a986f2c25ec023426b4fb222130af75f (patch)
treeb2fd726519f60975ffd2fef8365014b6f98b1b99 /src/math
parentafa2aaccea6e9f8c55809abb6471dc9aaa402711 (diff)
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math: fix atanh (overflow and underflow issues)
in atanh exception handling was left to the called log functions, but the argument to those functions could underflow or overflow. use double_t and float_t to avoid some useless stores on x86
Diffstat (limited to 'src/math')
-rw-r--r--src/math/atanh.c18
-rw-r--r--src/math/atanhf.c18
-rw-r--r--src/math/atanhl.c15
3 files changed, 37 insertions, 14 deletions
diff --git a/src/math/atanh.c b/src/math/atanh.c
index 84a84c69..63a035d7 100644
--- a/src/math/atanh.c
+++ b/src/math/atanh.c
@@ -6,16 +6,24 @@ double atanh(double x)
union {double f; uint64_t i;} u = {.f = x};
unsigned e = u.i >> 52 & 0x7ff;
unsigned s = u.i >> 63;
+ double_t y;
/* |x| */
u.i &= (uint64_t)-1/2;
- x = u.f;
+ y = u.f;
if (e < 0x3ff - 1) {
- /* |x| < 0.5, up to 1.7ulp error */
- x = 0.5*log1p(2*x + 2*x*x/(1-x));
+ if (e < 0x3ff - 32) {
+ /* handle underflow */
+ if (e == 0)
+ FORCE_EVAL((float)y);
+ } else {
+ /* |x| < 0.5, up to 1.7ulp error */
+ y = 0.5*log1p(2*y + 2*y*y/(1-y));
+ }
} else {
- x = 0.5*log1p(2*x/(1-x));
+ /* avoid overflow */
+ y = 0.5*log1p(2*(y/(1-y)));
}
- return s ? -x : x;
+ return s ? -y : y;
}
diff --git a/src/math/atanhf.c b/src/math/atanhf.c
index ca106efc..65f07c0f 100644
--- a/src/math/atanhf.c
+++ b/src/math/atanhf.c
@@ -5,16 +5,24 @@ float atanhf(float x)
{
union {float f; uint32_t i;} u = {.f = x};
unsigned s = u.i >> 31;
+ float_t y;
/* |x| */
u.i &= 0x7fffffff;
- x = u.f;
+ y = u.f;
if (u.i < 0x3f800000 - (1<<23)) {
- /* |x| < 0.5, up to 1.7ulp error */
- x = 0.5f*log1pf(2*x + 2*x*x/(1-x));
+ if (u.i < 0x3f800000 - (32<<23)) {
+ /* handle underflow */
+ if (u.i < (1<<23))
+ FORCE_EVAL((float)(y*y));
+ } else {
+ /* |x| < 0.5, up to 1.7ulp error */
+ y = 0.5f*log1pf(2*y + 2*y*y/(1-y));
+ }
} else {
- x = 0.5f*log1pf(2*x/(1-x));
+ /* avoid overflow */
+ y = 0.5f*log1pf(2*(y/(1-y)));
}
- return s ? -x : x;
+ return s ? -y : y;
}
diff --git a/src/math/atanhl.c b/src/math/atanhl.c
index 72a1e345..f63d60b1 100644
--- a/src/math/atanhl.c
+++ b/src/math/atanhl.c
@@ -17,11 +17,18 @@ long double atanhl(long double x)
u.i.se = e;
x = u.f;
- if (e < 0x3fff - 1) {
- /* |x| < 0.5, up to 1.7ulp error */
- x = 0.5*log1pl(2*x + 2*x*x/(1-x));
+ if (e < 0x3ff - 1) {
+ if (e < 0x3ff - LDBL_MANT_DIG/2) {
+ /* handle underflow */
+ if (e == 0)
+ FORCE_EVAL((float)x);
+ } else {
+ /* |x| < 0.5, up to 1.7ulp error */
+ x = 0.5*log1pl(2*x + 2*x*x/(1-x));
+ }
} else {
- x = 0.5*log1pl(2*x/(1-x));
+ /* avoid overflow */
+ x = 0.5*log1pl(2*(x/(1-x)));
}
return s ? -x : x;
}