<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/Users/erlendbasso/.cargo/registry/src/github.com-1ecc6299db9ec823/libm-0.2.6/src/math/lgammaf_r.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lgammaf_r.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceSerif4-Regular-1f7d512b176f0f72.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceSerif4-Bold-124a1ca42af929b6.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../../../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../../../static.files/rustdoc-6827029ac823cab7.css" id="mainThemeStyle"><link rel="stylesheet" id="themeStyle" href="../../../static.files/light-ebce58d0a40c3431.css"><link rel="stylesheet" disabled href="../../../static.files/dark-f23faae4a2daf9a6.css"><link rel="stylesheet" disabled href="../../../static.files/ayu-8af5e100b21cd173.css"><script id="default-settings" ></script><script src="../../../static.files/storage-d43fa987303ecbbb.js"></script><script defer src="../../../static.files/source-script-5cf2e01a42cc9858.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../static.files/main-c55e1eb52e1886b4.js"></script><noscript><link rel="stylesheet" href="../../../static.files/noscript-13285aec31fa243e.css"></noscript><link rel="alternate icon" type="image/png" href="../../../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../libm/index.html"><img class="rust-logo" src="../../../static.files/rust-logo-151179464ae7ed46.svg" alt="logo"></a><form class="search-form"><span></span><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../static.files/wheel-5ec35bf9ca753509.svg"></a></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><a href="#1" id="1">1</a>
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</pre><pre class="rust"><code><span class="comment">/* origin: FreeBSD /usr/src/lib/msun/src/e_lgammaf_r.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
</span><span class="kw">use super</span>::{floorf, k_cosf, k_sinf, logf};
<span class="kw">const </span>PI: f32 = <span class="number">3.1415927410e+00</span>; <span class="comment">/* 0x40490fdb */
</span><span class="kw">const </span>A0: f32 = <span class="number">7.7215664089e-02</span>; <span class="comment">/* 0x3d9e233f */
</span><span class="kw">const </span>A1: f32 = <span class="number">3.2246702909e-01</span>; <span class="comment">/* 0x3ea51a66 */
</span><span class="kw">const </span>A2: f32 = <span class="number">6.7352302372e-02</span>; <span class="comment">/* 0x3d89f001 */
</span><span class="kw">const </span>A3: f32 = <span class="number">2.0580807701e-02</span>; <span class="comment">/* 0x3ca89915 */
</span><span class="kw">const </span>A4: f32 = <span class="number">7.3855509982e-03</span>; <span class="comment">/* 0x3bf2027e */
</span><span class="kw">const </span>A5: f32 = <span class="number">2.8905137442e-03</span>; <span class="comment">/* 0x3b3d6ec6 */
</span><span class="kw">const </span>A6: f32 = <span class="number">1.1927076848e-03</span>; <span class="comment">/* 0x3a9c54a1 */
</span><span class="kw">const </span>A7: f32 = <span class="number">5.1006977446e-04</span>; <span class="comment">/* 0x3a05b634 */
</span><span class="kw">const </span>A8: f32 = <span class="number">2.2086278477e-04</span>; <span class="comment">/* 0x39679767 */
</span><span class="kw">const </span>A9: f32 = <span class="number">1.0801156895e-04</span>; <span class="comment">/* 0x38e28445 */
</span><span class="kw">const </span>A10: f32 = <span class="number">2.5214456400e-05</span>; <span class="comment">/* 0x37d383a2 */
</span><span class="kw">const </span>A11: f32 = <span class="number">4.4864096708e-05</span>; <span class="comment">/* 0x383c2c75 */
</span><span class="kw">const </span>TC: f32 = <span class="number">1.4616321325e+00</span>; <span class="comment">/* 0x3fbb16c3 */
</span><span class="kw">const </span>TF: f32 = -<span class="number">1.2148628384e-01</span>; <span class="comment">/* 0xbdf8cdcd */
/* TT = -(tail of TF) */
</span><span class="kw">const </span>TT: f32 = <span class="number">6.6971006518e-09</span>; <span class="comment">/* 0x31e61c52 */
</span><span class="kw">const </span>T0: f32 = <span class="number">4.8383611441e-01</span>; <span class="comment">/* 0x3ef7b95e */
</span><span class="kw">const </span>T1: f32 = -<span class="number">1.4758771658e-01</span>; <span class="comment">/* 0xbe17213c */
</span><span class="kw">const </span>T2: f32 = <span class="number">6.4624942839e-02</span>; <span class="comment">/* 0x3d845a15 */
</span><span class="kw">const </span>T3: f32 = -<span class="number">3.2788541168e-02</span>; <span class="comment">/* 0xbd064d47 */
</span><span class="kw">const </span>T4: f32 = <span class="number">1.7970675603e-02</span>; <span class="comment">/* 0x3c93373d */
</span><span class="kw">const </span>T5: f32 = -<span class="number">1.0314224288e-02</span>; <span class="comment">/* 0xbc28fcfe */
</span><span class="kw">const </span>T6: f32 = <span class="number">6.1005386524e-03</span>; <span class="comment">/* 0x3bc7e707 */
</span><span class="kw">const </span>T7: f32 = -<span class="number">3.6845202558e-03</span>; <span class="comment">/* 0xbb7177fe */
</span><span class="kw">const </span>T8: f32 = <span class="number">2.2596477065e-03</span>; <span class="comment">/* 0x3b141699 */
</span><span class="kw">const </span>T9: f32 = -<span class="number">1.4034647029e-03</span>; <span class="comment">/* 0xbab7f476 */
</span><span class="kw">const </span>T10: f32 = <span class="number">8.8108185446e-04</span>; <span class="comment">/* 0x3a66f867 */
</span><span class="kw">const </span>T11: f32 = -<span class="number">5.3859531181e-04</span>; <span class="comment">/* 0xba0d3085 */
</span><span class="kw">const </span>T12: f32 = <span class="number">3.1563205994e-04</span>; <span class="comment">/* 0x39a57b6b */
</span><span class="kw">const </span>T13: f32 = -<span class="number">3.1275415677e-04</span>; <span class="comment">/* 0xb9a3f927 */
</span><span class="kw">const </span>T14: f32 = <span class="number">3.3552918467e-04</span>; <span class="comment">/* 0x39afe9f7 */
</span><span class="kw">const </span>U0: f32 = -<span class="number">7.7215664089e-02</span>; <span class="comment">/* 0xbd9e233f */
</span><span class="kw">const </span>U1: f32 = <span class="number">6.3282704353e-01</span>; <span class="comment">/* 0x3f2200f4 */
</span><span class="kw">const </span>U2: f32 = <span class="number">1.4549225569e+00</span>; <span class="comment">/* 0x3fba3ae7 */
</span><span class="kw">const </span>U3: f32 = <span class="number">9.7771751881e-01</span>; <span class="comment">/* 0x3f7a4bb2 */
</span><span class="kw">const </span>U4: f32 = <span class="number">2.2896373272e-01</span>; <span class="comment">/* 0x3e6a7578 */
</span><span class="kw">const </span>U5: f32 = <span class="number">1.3381091878e-02</span>; <span class="comment">/* 0x3c5b3c5e */
</span><span class="kw">const </span>V1: f32 = <span class="number">2.4559779167e+00</span>; <span class="comment">/* 0x401d2ebe */
</span><span class="kw">const </span>V2: f32 = <span class="number">2.1284897327e+00</span>; <span class="comment">/* 0x4008392d */
</span><span class="kw">const </span>V3: f32 = <span class="number">7.6928514242e-01</span>; <span class="comment">/* 0x3f44efdf */
</span><span class="kw">const </span>V4: f32 = <span class="number">1.0422264785e-01</span>; <span class="comment">/* 0x3dd572af */
</span><span class="kw">const </span>V5: f32 = <span class="number">3.2170924824e-03</span>; <span class="comment">/* 0x3b52d5db */
</span><span class="kw">const </span>S0: f32 = -<span class="number">7.7215664089e-02</span>; <span class="comment">/* 0xbd9e233f */
</span><span class="kw">const </span>S1: f32 = <span class="number">2.1498242021e-01</span>; <span class="comment">/* 0x3e5c245a */
</span><span class="kw">const </span>S2: f32 = <span class="number">3.2577878237e-01</span>; <span class="comment">/* 0x3ea6cc7a */
</span><span class="kw">const </span>S3: f32 = <span class="number">1.4635047317e-01</span>; <span class="comment">/* 0x3e15dce6 */
</span><span class="kw">const </span>S4: f32 = <span class="number">2.6642270386e-02</span>; <span class="comment">/* 0x3cda40e4 */
</span><span class="kw">const </span>S5: f32 = <span class="number">1.8402845599e-03</span>; <span class="comment">/* 0x3af135b4 */
</span><span class="kw">const </span>S6: f32 = <span class="number">3.1947532989e-05</span>; <span class="comment">/* 0x3805ff67 */
</span><span class="kw">const </span>R1: f32 = <span class="number">1.3920053244e+00</span>; <span class="comment">/* 0x3fb22d3b */
</span><span class="kw">const </span>R2: f32 = <span class="number">7.2193557024e-01</span>; <span class="comment">/* 0x3f38d0c5 */
</span><span class="kw">const </span>R3: f32 = <span class="number">1.7193385959e-01</span>; <span class="comment">/* 0x3e300f6e */
</span><span class="kw">const </span>R4: f32 = <span class="number">1.8645919859e-02</span>; <span class="comment">/* 0x3c98bf54 */
</span><span class="kw">const </span>R5: f32 = <span class="number">7.7794247773e-04</span>; <span class="comment">/* 0x3a4beed6 */
</span><span class="kw">const </span>R6: f32 = <span class="number">7.3266842264e-06</span>; <span class="comment">/* 0x36f5d7bd */
</span><span class="kw">const </span>W0: f32 = <span class="number">4.1893854737e-01</span>; <span class="comment">/* 0x3ed67f1d */
</span><span class="kw">const </span>W1: f32 = <span class="number">8.3333335817e-02</span>; <span class="comment">/* 0x3daaaaab */
</span><span class="kw">const </span>W2: f32 = -<span class="number">2.7777778450e-03</span>; <span class="comment">/* 0xbb360b61 */
</span><span class="kw">const </span>W3: f32 = <span class="number">7.9365057172e-04</span>; <span class="comment">/* 0x3a500cfd */
</span><span class="kw">const </span>W4: f32 = -<span class="number">5.9518753551e-04</span>; <span class="comment">/* 0xba1c065c */
</span><span class="kw">const </span>W5: f32 = <span class="number">8.3633989561e-04</span>; <span class="comment">/* 0x3a5b3dd2 */
</span><span class="kw">const </span>W6: f32 = -<span class="number">1.6309292987e-03</span>; <span class="comment">/* 0xbad5c4e8 */
/* sin(PI*x) assuming x > 2^-100, if sin(PI*x)==0 the sign is arbitrary */
</span><span class="kw">fn </span>sin_pi(<span class="kw-2">mut </span>x: f32) -> f32 {
<span class="kw">let </span><span class="kw-2">mut </span>y: f64;
<span class="kw">let </span><span class="kw-2">mut </span>n: isize;
<span class="comment">/* spurious inexact if odd int */
</span>x = <span class="number">2.0 </span>* (x * <span class="number">0.5 </span>- floorf(x * <span class="number">0.5</span>)); <span class="comment">/* x mod 2.0 */
</span>n = (x * <span class="number">4.0</span>) <span class="kw">as </span>isize;
n = <span class="macro">div!</span>(n + <span class="number">1</span>, <span class="number">2</span>);
y = (x <span class="kw">as </span>f64) - (n <span class="kw">as </span>f64) * <span class="number">0.5</span>;
y <span class="kw-2">*</span>= <span class="number">3.14159265358979323846</span>;
<span class="kw">match </span>n {
<span class="number">1 </span>=> k_cosf(y),
<span class="number">2 </span>=> k_sinf(-y),
<span class="number">3 </span>=> -k_cosf(y),
<span class="number">0 </span>| <span class="kw">_ </span>=> k_sinf(y),
}
}
<span class="attr">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
</span><span class="kw">pub fn </span>lgammaf_r(<span class="kw-2">mut </span>x: f32) -> (f32, i32) {
<span class="kw">let </span>u = x.to_bits();
<span class="kw">let </span><span class="kw-2">mut </span>t: f32;
<span class="kw">let </span>y: f32;
<span class="kw">let </span><span class="kw-2">mut </span>z: f32;
<span class="kw">let </span>nadj: f32;
<span class="kw">let </span>p: f32;
<span class="kw">let </span>p1: f32;
<span class="kw">let </span>p2: f32;
<span class="kw">let </span>p3: f32;
<span class="kw">let </span>q: f32;
<span class="kw">let </span><span class="kw-2">mut </span>r: f32;
<span class="kw">let </span>w: f32;
<span class="kw">let </span>ix: u32;
<span class="kw">let </span>i: i32;
<span class="kw">let </span>sign: bool;
<span class="kw">let </span><span class="kw-2">mut </span>signgam: i32;
<span class="comment">/* purge off +-inf, NaN, +-0, tiny and negative arguments */
</span>signgam = <span class="number">1</span>;
sign = (u >> <span class="number">31</span>) != <span class="number">0</span>;
ix = u & <span class="number">0x7fffffff</span>;
<span class="kw">if </span>ix >= <span class="number">0x7f800000 </span>{
<span class="kw">return </span>(x * x, signgam);
}
<span class="kw">if </span>ix < <span class="number">0x35000000 </span>{
<span class="comment">/* |x| < 2**-21, return -log(|x|) */
</span><span class="kw">if </span>sign {
signgam = -<span class="number">1</span>;
x = -x;
}
<span class="kw">return </span>(-logf(x), signgam);
}
<span class="kw">if </span>sign {
x = -x;
t = sin_pi(x);
<span class="kw">if </span>t == <span class="number">0.0 </span>{
<span class="comment">/* -integer */
</span><span class="kw">return </span>(<span class="number">1.0 </span>/ (x - x), signgam);
}
<span class="kw">if </span>t > <span class="number">0.0 </span>{
signgam = -<span class="number">1</span>;
} <span class="kw">else </span>{
t = -t;
}
nadj = logf(PI / (t * x));
} <span class="kw">else </span>{
nadj = <span class="number">0.0</span>;
}
<span class="comment">/* purge off 1 and 2 */
</span><span class="kw">if </span>ix == <span class="number">0x3f800000 </span>|| ix == <span class="number">0x40000000 </span>{
r = <span class="number">0.0</span>;
}
<span class="comment">/* for x < 2.0 */
</span><span class="kw">else if </span>ix < <span class="number">0x40000000 </span>{
<span class="kw">if </span>ix <= <span class="number">0x3f666666 </span>{
<span class="comment">/* lgamma(x) = lgamma(x+1)-log(x) */
</span>r = -logf(x);
<span class="kw">if </span>ix >= <span class="number">0x3f3b4a20 </span>{
y = <span class="number">1.0 </span>- x;
i = <span class="number">0</span>;
} <span class="kw">else if </span>ix >= <span class="number">0x3e6d3308 </span>{
y = x - (TC - <span class="number">1.0</span>);
i = <span class="number">1</span>;
} <span class="kw">else </span>{
y = x;
i = <span class="number">2</span>;
}
} <span class="kw">else </span>{
r = <span class="number">0.0</span>;
<span class="kw">if </span>ix >= <span class="number">0x3fdda618 </span>{
<span class="comment">/* [1.7316,2] */
</span>y = <span class="number">2.0 </span>- x;
i = <span class="number">0</span>;
} <span class="kw">else if </span>ix >= <span class="number">0x3F9da620 </span>{
<span class="comment">/* [1.23,1.73] */
</span>y = x - TC;
i = <span class="number">1</span>;
} <span class="kw">else </span>{
y = x - <span class="number">1.0</span>;
i = <span class="number">2</span>;
}
}
<span class="kw">match </span>i {
<span class="number">0 </span>=> {
z = y * y;
p1 = A0 + z * (A2 + z * (A4 + z * (A6 + z * (A8 + z * A10))));
p2 = z * (A1 + z * (A3 + z * (A5 + z * (A7 + z * (A9 + z * A11)))));
p = y * p1 + p2;
r += p - <span class="number">0.5 </span>* y;
}
<span class="number">1 </span>=> {
z = y * y;
w = z * y;
p1 = T0 + w * (T3 + w * (T6 + w * (T9 + w * T12))); <span class="comment">/* parallel comp */
</span>p2 = T1 + w * (T4 + w * (T7 + w * (T10 + w * T13)));
p3 = T2 + w * (T5 + w * (T8 + w * (T11 + w * T14)));
p = z * p1 - (TT - w * (p2 + y * p3));
r += TF + p;
}
<span class="number">2 </span>=> {
p1 = y * (U0 + y * (U1 + y * (U2 + y * (U3 + y * (U4 + y * U5)))));
p2 = <span class="number">1.0 </span>+ y * (V1 + y * (V2 + y * (V3 + y * (V4 + y * V5))));
r += -<span class="number">0.5 </span>* y + p1 / p2;
}
<span class="attr">#[cfg(debug_assertions)]
</span><span class="kw">_ </span>=> <span class="macro">unreachable!</span>(),
<span class="attr">#[cfg(not(debug_assertions))]
</span><span class="kw">_ </span>=> {}
}
} <span class="kw">else if </span>ix < <span class="number">0x41000000 </span>{
<span class="comment">/* x < 8.0 */
</span>i = x <span class="kw">as </span>i32;
y = x - (i <span class="kw">as </span>f32);
p = y * (S0 + y * (S1 + y * (S2 + y * (S3 + y * (S4 + y * (S5 + y * S6))))));
q = <span class="number">1.0 </span>+ y * (R1 + y * (R2 + y * (R3 + y * (R4 + y * (R5 + y * R6)))));
r = <span class="number">0.5 </span>* y + p / q;
z = <span class="number">1.0</span>; <span class="comment">/* lgamma(1+s) = log(s) + lgamma(s) */
// TODO: In C, this was implemented using switch jumps with fallthrough.
// Does this implementation have performance problems?
</span><span class="kw">if </span>i >= <span class="number">7 </span>{
z <span class="kw-2">*</span>= y + <span class="number">6.0</span>;
}
<span class="kw">if </span>i >= <span class="number">6 </span>{
z <span class="kw-2">*</span>= y + <span class="number">5.0</span>;
}
<span class="kw">if </span>i >= <span class="number">5 </span>{
z <span class="kw-2">*</span>= y + <span class="number">4.0</span>;
}
<span class="kw">if </span>i >= <span class="number">4 </span>{
z <span class="kw-2">*</span>= y + <span class="number">3.0</span>;
}
<span class="kw">if </span>i >= <span class="number">3 </span>{
z <span class="kw-2">*</span>= y + <span class="number">2.0</span>;
r += logf(z);
}
} <span class="kw">else if </span>ix < <span class="number">0x5c800000 </span>{
<span class="comment">/* 8.0 <= x < 2**58 */
</span>t = logf(x);
z = <span class="number">1.0 </span>/ x;
y = z * z;
w = W0 + z * (W1 + y * (W2 + y * (W3 + y * (W4 + y * (W5 + y * W6)))));
r = (x - <span class="number">0.5</span>) * (t - <span class="number">1.0</span>) + w;
} <span class="kw">else </span>{
<span class="comment">/* 2**58 <= x <= inf */
</span>r = x * (logf(x) - <span class="number">1.0</span>);
}
<span class="kw">if </span>sign {
r = nadj - r;
}
<span class="kw">return </span>(r, signgam);
}
</code></pre></div>
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