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authorSzabolcs Nagy <nsz@port70.net>2012-11-18 03:42:09 +0100
committerSzabolcs Nagy <nsz@port70.net>2012-11-18 03:42:09 +0100
commitab1772c597ba8fe0c26400256b12d7a4df23880e (patch)
treeaa9e9df0cb237e2fdf3847300b9fc6b9547fc240 /src/math/exp.c
parent159c7655d06f04aa56a57385d633699c4c63d72c (diff)
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math: expf.c cleanup
similar to exp.c cleanup: use scalbnf, don't return excess precision, drop some optimizatoins. exp.c was changed to be more consistent with expf.c code.
Diffstat (limited to 'src/math/exp.c')
-rw-r--r--src/math/exp.c20
1 files changed, 11 insertions, 9 deletions
diff --git a/src/math/exp.c b/src/math/exp.c
index 5c0edee4..5ec8f8a7 100644
--- a/src/math/exp.c
+++ b/src/math/exp.c
@@ -80,7 +80,7 @@ P5 = 4.13813679705723846039e-08; /* 0x3E663769, 0x72BEA4D0 */
double exp(double x)
{
- double hi, lo, c, z;
+ double hi, lo, c, xx;
int k, sign;
uint32_t hx;
@@ -92,24 +92,26 @@ double exp(double x)
if (hx >= 0x40862e42) { /* if |x| >= 709.78... */
if (isnan(x))
return x;
+ if (hx == 0x7ff00000 && sign) /* -inf */
+ return 0;
if (x > 709.782712893383973096) {
/* overflow if x!=inf */
STRICT_ASSIGN(double, x, 0x1p1023 * x);
return x;
}
if (x < -745.13321910194110842) {
- /* underflow if x!=-inf */
- STRICT_ASSIGN(double, x, 0x1p-1000 / -x * 0x1p-1000);
+ /* underflow */
+ STRICT_ASSIGN(double, x, 0x1p-1000 * 0x1p-1000);
return x;
}
}
/* argument reduction */
if (hx > 0x3fd62e42) { /* if |x| > 0.5 ln2 */
- if (hx < 0x3ff0a2b2) /* if |x| < 1.5 ln2 */
- k = 1 - sign - sign; /* optimization */
- else
+ if (hx >= 0x3ff0a2b2) /* if |x| >= 1.5 ln2 */
k = (int)(invln2*x + half[sign]);
+ else
+ k = 1 - sign - sign;
hi = x - k*ln2hi; /* k*ln2hi is exact here */
lo = k*ln2lo;
STRICT_ASSIGN(double, x, hi - lo);
@@ -124,9 +126,9 @@ double exp(double x)
}
/* x is now in primary range */
- z = x*x;
- c = x - z*(P1+z*(P2+z*(P3+z*(P4+z*P5))));
- x = 1 + ((x*c/(2-c) - lo) + hi);
+ xx = x*x;
+ c = x - xx*(P1+xx*(P2+xx*(P3+xx*(P4+xx*P5))));
+ x = 1 + (x*c/(2-c) - lo + hi);
if (k == 0)
return x;
return scalbn(x, k);