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(__ieee754_lgammal_r): Remove test for negative integer arg; sin_pi does it correctly.

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This commit is contained in:
Andreas Jaeger 2002-01-28 10:18:33 +00:00
parent fbee8a1eb1
commit 98dee2c20d
1 changed files with 8 additions and 10 deletions
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16
sysdeps/ieee754/ldbl-96/e_lgammal_r.c
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@ -18,9 +18,9 @@
*
* Method:
* 1. Argument Reduction for 0 < x <= 8
* Since gamma(1+s)=s*gamma(s), for x in [0,8], we may
* reduce x to a number in [1.5,2.5] by
* lgamma(1+s) = log(s) + lgamma(s)
* Since gamma(1+s)=s*gamma(s), for x in [0,8], we may
* reduce x to a number in [1.5,2.5] by
* lgamma(1+s) = log(s) + lgamma(s)
* for example,
* lgamma(7.3) = log(6.3) + lgamma(6.3)
* = log(6.3*5.3) + lgamma(5.3)
@ -50,13 +50,13 @@
* Let z = 1/x, then we approximation
* f(z) = lgamma(x) - (x-0.5)(log(x)-1)
* by
* 3 5 11
* 3 5 11
* w = w0 + w1*z + w2*z + w3*z + ... + w6*z
*
* 4. For negative x, since (G is gamma function)
* -x*G(-x)*G(x) = pi/sin(pi*x),
* we have
* G(x) = pi/(sin(pi*x)*(-x)*G(-x))
* we have
* G(x) = pi/(sin(pi*x)*(-x)*G(-x))
* since G(-x) is positive, sign(G(x)) = sign(sin(pi*x)) for x<0
* Hence, for x<0, signgam = sign(sin(pi*x)) and
* lgamma(x) = log(|Gamma(x)|)
@ -69,7 +69,7 @@
* lgamma(1)=lgamma(2)=0
* lgamma(x) ~ -log(x) for tiny x
* lgamma(0) = lgamma(inf) = inf
* lgamma(-integer) = +-inf
* lgamma(-integer) = +-inf
*
*/
@ -304,8 +304,6 @@ __ieee754_lgammal_r (x, signgamp)
}
if (se & 0x8000)
{
if (x == __floorl(x))
return x / zero;
t = sin_pi (x);
if (t == zero)
return one / fabsl (t); /* -integer */