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math: fix a regression in powl and do some cleanups

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previously a division was accidentally turned into integer div
(w = -i/NXT;) instead of long double div (w = -i; w /= NXT;)
This commit is contained in:
nsz 2012-03-27 22:49:37 +02:00
parent bbfbc7edaf
commit cf682072ce
1 changed files with 11 additions and 12 deletions
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23
src/math/powl.c
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@ -165,8 +165,6 @@ static const long double R[] = {
6.9314718055994530931447E-1L,
};
#define douba(k) A[k]
#define doubb(k) B[k]
#define MEXP (NXT*16384.0L)
/* The following if denormal numbers are supported, else -MEXP: */
#define MNEXP (-NXT*(16384.0L+64.0L))
@ -300,15 +298,15 @@ long double powl(long double x, long double y)
/* find significand in antilog table A[] */
i = 1;
if (x <= douba(17))
if (x <= A[17])
i = 17;
if (x <= douba(i+8))
if (x <= A[i+8])
i += 8;
if (x <= douba(i+4))
if (x <= A[i+4])
i += 4;
if (x <= douba(i+2))
if (x <= A[i+2])
i += 2;
if (x >= douba(1))
if (x >= A[1])
i = -1;
i += 1;
@ -319,9 +317,9 @@ long double powl(long double x, long double y)
*
* log(x/a) = log(1+v), v = x/a - 1 = (x-a)/a
*/
x -= douba(i);
x -= doubb(i/2);
x /= douba(i);
x -= A[i];
x -= B[i/2];
x /= A[i];
/* rational approximation for log(1+v):
*
@ -340,7 +338,8 @@ long double powl(long double x, long double y)
z += x;
/* Compute exponent term of the base 2 logarithm. */
w = -i / NXT;
w = -i;
w /= NXT;
w += e;
/* Now base 2 log of x is w + z. */
@ -397,7 +396,7 @@ long double powl(long double x, long double y)
i = 1;
i = e/NXT + i;
e = NXT*i - e;
w = douba(e);
w = A[e];
z = w * z; /* 2**-e * ( 1 + (2**Hb-1) ) */
z = z + w;
z = scalbnl(z, i); /* multiply by integer power of 2 */