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Merge pull request #3045 from JohanEngelen/gamma64bit

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std.mathspecial: for 64-bit reals, provide MAXGAMMA, MAXLOG, and MINLOG
This commit is contained in:
Iain Buclaw 2015-07-30 08:42:57 +02:00
commit 89f53cb619
1 changed files with 30 additions and 4 deletions
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34
std/internal/math/gammafunction.d
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@ -111,7 +111,19 @@ real gammaStirling(real x)
}
else {
w = 1.0L + w * poly( w, SmallStirlingCoeffs);
y = pow( x, x - 0.5L ) / y;
static if (floatTraits!(real).realFormat == RealFormat.ieeeDouble) {
// Avoid overflow in pow() for 64-bit reals
if (x > 143.0) {
real v = pow( x, 0.5 * x - 0.25 );
y = v * (v / y);
}
else {
y = pow( x, x - 0.5 ) / y;
}
}
else {
y = pow( x, x - 0.5L ) / y;
}
}
y = SQRT2PI * y * w;
return y;
@ -231,7 +243,12 @@ real igammaTemmeLarge(real a, real x)
public:
/// The maximum value of x for which gamma(x) < real.infinity.
enum real MAXGAMMA = 1755.5483429L;
static if (floatTraits!(real).realFormat == RealFormat.ieeeExtended)
enum real MAXGAMMA = 1755.5483429L;
else static if (floatTraits!(real).realFormat == RealFormat.ieeeDouble)
enum real MAXGAMMA = 171.6243769L;
else
static assert(0, "missing MAXGAMMA for other real types");
/*****************************************************
@ -531,8 +548,17 @@ unittest {
private {
enum real MAXLOG = 0x1.62e42fefa39ef358p+13L; // log(real.max)
enum real MINLOG = -0x1.6436716d5406e6d8p+13L; // log(real.min*real.epsilon) = log(smallest denormal)
static if (floatTraits!(real).realFormat == RealFormat.ieeeExtended) {
enum real MAXLOG = 0x1.62e42fefa39ef358p+13L; // log(real.max)
enum real MINLOG = -0x1.6436716d5406e6d8p+13L; // log(real.min_normal*real.epsilon) = log(smallest denormal)
}
else static if (floatTraits!(real).realFormat == RealFormat.ieeeDouble) {
enum real MAXLOG = 0x1.62e42fefa39efp+9L; // log(real.max)
enum real MINLOG = -0x1.74385446d71c3p+9L; // log(real.min_normal*real.epsilon) = log(smallest denormal)
}
else
static assert(0, "missing MAXLOG and MINLOG for other real types");
enum real BETA_BIG = 9.223372036854775808e18L;
enum real BETA_BIGINV = 1.084202172485504434007e-19L;
}