| <!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 `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/libm-0.2.7/src/math/sqrtf.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>sqrtf.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.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"><a class="sidebar-logo" href="../../../libm/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../libm/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" 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="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="comment">/* origin: FreeBSD /usr/src/lib/msun/src/e_sqrtf.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="attribute">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| </span><span class="kw">pub fn </span>sqrtf(x: f32) -> f32 { |
| <span class="comment">// On wasm32 we know that LLVM's intrinsic will compile to an optimized |
| // `f32.sqrt` native instruction, so we can leverage this for both code size |
| // and speed. |
| </span><span class="macro">llvm_intrinsically_optimized! </span>{ |
| <span class="attribute">#[cfg(target_arch = <span class="string">"wasm32"</span>)] </span>{ |
| <span class="kw">return if </span>x < <span class="number">0.0 </span>{ |
| ::core::f32::NAN |
| } <span class="kw">else </span>{ |
| <span class="kw">unsafe </span>{ ::core::intrinsics::sqrtf32(x) } |
| } |
| } |
| } |
| <span class="attribute">#[cfg(target_feature = <span class="string">"sse"</span>)] |
| </span>{ |
| <span class="comment">// Note: This path is unlikely since LLVM will usually have already |
| // optimized sqrt calls into hardware instructions if sse is available, |
| // but if someone does end up here they'll apprected the speed increase. |
| </span><span class="attribute">#[cfg(target_arch = <span class="string">"x86"</span>)] |
| </span><span class="kw">use </span>core::arch::x86::<span class="kw-2">*</span>; |
| <span class="attribute">#[cfg(target_arch = <span class="string">"x86_64"</span>)] |
| </span><span class="kw">use </span>core::arch::x86_64::<span class="kw-2">*</span>; |
| <span class="kw">unsafe </span>{ |
| <span class="kw">let </span>m = _mm_set_ss(x); |
| <span class="kw">let </span>m_sqrt = _mm_sqrt_ss(m); |
| _mm_cvtss_f32(m_sqrt) |
| } |
| } |
| <span class="attribute">#[cfg(not(target_feature = <span class="string">"sse"</span>))] |
| </span>{ |
| <span class="kw">const </span>TINY: f32 = <span class="number">1.0e-30</span>; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>z: f32; |
| <span class="kw">let </span>sign: i32 = <span class="number">0x80000000u32 </span><span class="kw">as </span>i32; |
| <span class="kw">let </span><span class="kw-2">mut </span>ix: i32; |
| <span class="kw">let </span><span class="kw-2">mut </span>s: i32; |
| <span class="kw">let </span><span class="kw-2">mut </span>q: i32; |
| <span class="kw">let </span><span class="kw-2">mut </span>m: i32; |
| <span class="kw">let </span><span class="kw-2">mut </span>t: i32; |
| <span class="kw">let </span><span class="kw-2">mut </span>i: i32; |
| <span class="kw">let </span><span class="kw-2">mut </span>r: u32; |
| |
| ix = x.to_bits() <span class="kw">as </span>i32; |
| |
| <span class="comment">/* take care of Inf and NaN */ |
| </span><span class="kw">if </span>(ix <span class="kw">as </span>u32 & <span class="number">0x7f800000</span>) == <span class="number">0x7f800000 </span>{ |
| <span class="kw">return </span>x * x + x; <span class="comment">/* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */ |
| </span>} |
| |
| <span class="comment">/* take care of zero */ |
| </span><span class="kw">if </span>ix <= <span class="number">0 </span>{ |
| <span class="kw">if </span>(ix & !sign) == <span class="number">0 </span>{ |
| <span class="kw">return </span>x; <span class="comment">/* sqrt(+-0) = +-0 */ |
| </span>} |
| <span class="kw">if </span>ix < <span class="number">0 </span>{ |
| <span class="kw">return </span>(x - x) / (x - x); <span class="comment">/* sqrt(-ve) = sNaN */ |
| </span>} |
| } |
| |
| <span class="comment">/* normalize x */ |
| </span>m = ix >> <span class="number">23</span>; |
| <span class="kw">if </span>m == <span class="number">0 </span>{ |
| <span class="comment">/* subnormal x */ |
| </span>i = <span class="number">0</span>; |
| <span class="kw">while </span>ix & <span class="number">0x00800000 </span>== <span class="number">0 </span>{ |
| ix <<= <span class="number">1</span>; |
| i = i + <span class="number">1</span>; |
| } |
| m -= i - <span class="number">1</span>; |
| } |
| m -= <span class="number">127</span>; <span class="comment">/* unbias exponent */ |
| </span>ix = (ix & <span class="number">0x007fffff</span>) | <span class="number">0x00800000</span>; |
| <span class="kw">if </span>m & <span class="number">1 </span>== <span class="number">1 </span>{ |
| <span class="comment">/* odd m, double x to make it even */ |
| </span>ix += ix; |
| } |
| m >>= <span class="number">1</span>; <span class="comment">/* m = [m/2] */ |
| |
| /* generate sqrt(x) bit by bit */ |
| </span>ix += ix; |
| q = <span class="number">0</span>; |
| s = <span class="number">0</span>; |
| r = <span class="number">0x01000000</span>; <span class="comment">/* r = moving bit from right to left */ |
| |
| </span><span class="kw">while </span>r != <span class="number">0 </span>{ |
| t = s + r <span class="kw">as </span>i32; |
| <span class="kw">if </span>t <= ix { |
| s = t + r <span class="kw">as </span>i32; |
| ix -= t; |
| q += r <span class="kw">as </span>i32; |
| } |
| ix += ix; |
| r >>= <span class="number">1</span>; |
| } |
| |
| <span class="comment">/* use floating add to find out rounding direction */ |
| </span><span class="kw">if </span>ix != <span class="number">0 </span>{ |
| z = <span class="number">1.0 </span>- TINY; <span class="comment">/* raise inexact flag */ |
| </span><span class="kw">if </span>z >= <span class="number">1.0 </span>{ |
| z = <span class="number">1.0 </span>+ TINY; |
| <span class="kw">if </span>z > <span class="number">1.0 </span>{ |
| q += <span class="number">2</span>; |
| } <span class="kw">else </span>{ |
| q += q & <span class="number">1</span>; |
| } |
| } |
| } |
| |
| ix = (q >> <span class="number">1</span>) + <span class="number">0x3f000000</span>; |
| ix += m << <span class="number">23</span>; |
| f32::from_bits(ix <span class="kw">as </span>u32) |
| } |
| } |
| |
| <span class="comment">// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520 |
| </span><span class="attribute">#[cfg(not(target_arch = <span class="string">"powerpc64"</span>))] |
| #[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| <span class="kw">use </span>core::f32::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>sanity_check() { |
| <span class="macro">assert_eq!</span>(sqrtf(<span class="number">100.0</span>), <span class="number">10.0</span>); |
| <span class="macro">assert_eq!</span>(sqrtf(<span class="number">4.0</span>), <span class="number">2.0</span>); |
| } |
| |
| <span class="doccomment">/// The spec: https://en.cppreference.com/w/cpp/numeric/math/sqrt |
| </span><span class="attribute">#[test] |
| </span><span class="kw">fn </span>spec_tests() { |
| <span class="comment">// Not Asserted: FE_INVALID exception is raised if argument is negative. |
| </span><span class="macro">assert!</span>(sqrtf(-<span class="number">1.0</span>).is_nan()); |
| <span class="macro">assert!</span>(sqrtf(NAN).is_nan()); |
| <span class="kw">for </span>f <span class="kw">in </span>[<span class="number">0.0</span>, -<span class="number">0.0</span>, INFINITY].iter().copied() { |
| <span class="macro">assert_eq!</span>(sqrtf(f), f); |
| } |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>conformance_tests() { |
| <span class="kw">let </span>values = [ |
| <span class="number">3.14159265359f32</span>, |
| <span class="number">10000.0f32</span>, |
| f32::from_bits(<span class="number">0x0000000f</span>), |
| INFINITY, |
| ]; |
| <span class="kw">let </span>results = [<span class="number">1071833029u32</span>, <span class="number">1120403456u32</span>, <span class="number">456082799u32</span>, <span class="number">2139095040u32</span>]; |
| |
| <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..values.len() { |
| <span class="kw">let </span>bits = f32::to_bits(sqrtf(values[i])); |
| <span class="macro">assert_eq!</span>(results[i], bits); |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="libm" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
