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1f8e5847df
The current gamma, gamma_r, gammaf and gammaf_r functions return
|gamma(x)| instead of ln(|gamma(x)|) due to a change made back in 2002
to the __ieee754_gamma_r implementation. This patch fixes that, making
all of these functions map too their lgamma equivalents.
To fix the underlying bug, the __ieee754_gamma functions have been
changed to return gamma(x), removing the _r variants as those are no
longer necessary. Their names have been changed to __ieee754_tgamma to
avoid potential confusion from users.
Now that the __ieee754_tgamma functions return the correctly signed
value, the tgamma functions have been modified to use them.
libm.a now exposes the following gamma functions:
ln(|gamma(x)|):
__ieee754_lgamma_r
__ieee754_lgammaf_r
lgamma
lgamma_r
gamma
gamma_r
lgammaf
lgammaf_r
gammaf
gammaf_r
lgammal (on machines where long double is double)
gamma(x):
__ieee754_tgamma
__ieee754_tgammaf
tgamma
tgammaf
tgammal (on machines where long double is double)
Additional aliases for any of the above functions can be added if
necessary; in particular, I'm not sure if we need to include
__ieee754_gamma*_r functions (which would return ln(|(gamma(x)|).
Signed-off-by: Keith Packard <keithp@keithp.com>
----
v2:
Switch commit message to ASCII
47 lines
1.0 KiB
C
47 lines
1.0 KiB
C
/* @(#)w_gamma.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/* double gamma(double x)
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* Return the logarithm of the Gamma function of x or the Gamma function of x,
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* depending on the library mode.
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*/
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double tgamma(double x)
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#else
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double tgamma(x)
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double x;
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#endif
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{
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double y;
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y = __ieee754_tgamma(x);
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#ifdef _IEEE_LIBM
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return y;
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#else
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if(_LIB_VERSION == _IEEE_) return y;
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if(!finite(y)&&finite(x)) {
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if(floor(x)==x&&x<=0.0)
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return __kernel_standard(x,x,41); /* tgamma pole */
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else
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return __kernel_standard(x,x,40); /* tgamma overflow */
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}
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return y;
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#endif
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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