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<!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="Calculation of phi, derived from the Cumulative distribution function for N(mean, stdDeviation) normal distribution, given by 1.0 / (1.0 + math.exp(-y * (1.5976 + 0.070566 * y * y))) where y = (x - mean) / standard_deviation This is an approximation defined in β Mathematics Handbook (Logistic approximation). Error is 0.00014 at +- 3.16 The calculated value is equivalent to -log10(1 - CDF(y))"><title>phi in meta_srv::failure_detector - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-17e0aaed.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="meta_srv" data-themes="" data-resource-suffix="" data-rustdoc-version="1.96.0-nightly (ac7f9ec7d 2026-03-20)" data-channel="nightly" data-search-js="search-63369b7b.js" data-stringdex-js="stringdex-2da4960a.js" data-settings-js="settings-170eb4bf.js" ><script src="../../static.files/storage-41dd4d93.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../static.files/main-5013f961.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-f7c3ffd8.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-044be391.svg"></head><body class="rustdoc fn"><a class="skip-main-content" href="#main-content">Skip to main content</a><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><rustdoc-topbar><h2><a href="#">phi</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../meta_srv/index.html">meta_<wbr>srv</a><span class="version">1.0.0</span></h2></div><div class="sidebar-elems"><div id="rustdoc-modnav"><h2><a href="index.html">In meta_<wbr>srv::<wbr>failure_<wbr>detector</a></h2></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content" tabindex="-1"><div class="main-heading"><div class="rustdoc-breadcrumbs"><a href="../index.html">meta_srv</a>::<wbr><a href="index.html">failure_detector</a></div><h1>Function <span class="fn">phi</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../../src/meta_srv/failure_detector.rs.html#175-186">Source</a> </span></div><pre class="rust item-decl"><code>fn phi(time_diff: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i64.html">i64</a>, mean: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f64.html">f64</a>, std_deviation: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f64.html">f64</a>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f64.html">f64</a></code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Calculation of phi, derived from the Cumulative distribution function for
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N(mean, stdDeviation) normal distribution, given by
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1.0 / (1.0 + math.exp(-y * (1.5976 + 0.070566 * y * y)))
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where y = (x - mean) / standard_deviation
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This is an approximation defined in β Mathematics Handbook (Logistic approximation).
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Error is 0.00014 at +- 3.16
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The calculated value is equivalent to -log10(1 - CDF(y))</p>
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<p>Usually phi = 1 means likeliness that we will make a mistake is about 10%.
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The likeliness is about 1% with phi = 2, 0.1% with phi = 3 and so on.</p>
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</div></details></section></div></main></body></html> |