blob: 59a04f5c62d962b065c95c7b74b4187b26de4717 [file] [log] [blame]
<!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/git/checkouts/rulinalg-309246e5a94bf5cf/1ed8b93/src/matrix/decomposition/qr.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>qr.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="../../../../rulinalg/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="../../../../rulinalg/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>
<span id="2">2</span>
<span id="3">3</span>
<span id="4">4</span>
<span id="5">5</span>
<span id="6">6</span>
<span id="7">7</span>
<span id="8">8</span>
<span id="9">9</span>
<span id="10">10</span>
<span id="11">11</span>
<span id="12">12</span>
<span id="13">13</span>
<span id="14">14</span>
<span id="15">15</span>
<span id="16">16</span>
<span id="17">17</span>
<span id="18">18</span>
<span id="19">19</span>
<span id="20">20</span>
<span id="21">21</span>
<span id="22">22</span>
<span id="23">23</span>
<span id="24">24</span>
<span id="25">25</span>
<span id="26">26</span>
<span id="27">27</span>
<span id="28">28</span>
<span id="29">29</span>
<span id="30">30</span>
<span id="31">31</span>
<span id="32">32</span>
<span id="33">33</span>
<span id="34">34</span>
<span id="35">35</span>
<span id="36">36</span>
<span id="37">37</span>
<span id="38">38</span>
<span id="39">39</span>
<span id="40">40</span>
<span id="41">41</span>
<span id="42">42</span>
<span id="43">43</span>
<span id="44">44</span>
<span id="45">45</span>
<span id="46">46</span>
<span id="47">47</span>
<span id="48">48</span>
<span id="49">49</span>
<span id="50">50</span>
<span id="51">51</span>
<span id="52">52</span>
<span id="53">53</span>
<span id="54">54</span>
<span id="55">55</span>
<span id="56">56</span>
<span id="57">57</span>
<span id="58">58</span>
<span id="59">59</span>
<span id="60">60</span>
<span id="61">61</span>
<span id="62">62</span>
<span id="63">63</span>
<span id="64">64</span>
<span id="65">65</span>
<span id="66">66</span>
<span id="67">67</span>
<span id="68">68</span>
<span id="69">69</span>
<span id="70">70</span>
<span id="71">71</span>
<span id="72">72</span>
<span id="73">73</span>
<span id="74">74</span>
<span id="75">75</span>
<span id="76">76</span>
<span id="77">77</span>
<span id="78">78</span>
<span id="79">79</span>
<span id="80">80</span>
<span id="81">81</span>
<span id="82">82</span>
<span id="83">83</span>
<span id="84">84</span>
<span id="85">85</span>
<span id="86">86</span>
<span id="87">87</span>
<span id="88">88</span>
<span id="89">89</span>
<span id="90">90</span>
<span id="91">91</span>
<span id="92">92</span>
<span id="93">93</span>
<span id="94">94</span>
<span id="95">95</span>
<span id="96">96</span>
<span id="97">97</span>
<span id="98">98</span>
<span id="99">99</span>
<span id="100">100</span>
<span id="101">101</span>
<span id="102">102</span>
<span id="103">103</span>
<span id="104">104</span>
<span id="105">105</span>
<span id="106">106</span>
<span id="107">107</span>
<span id="108">108</span>
<span id="109">109</span>
<span id="110">110</span>
<span id="111">111</span>
<span id="112">112</span>
<span id="113">113</span>
<span id="114">114</span>
<span id="115">115</span>
<span id="116">116</span>
<span id="117">117</span>
<span id="118">118</span>
<span id="119">119</span>
<span id="120">120</span>
<span id="121">121</span>
<span id="122">122</span>
<span id="123">123</span>
<span id="124">124</span>
<span id="125">125</span>
<span id="126">126</span>
<span id="127">127</span>
<span id="128">128</span>
<span id="129">129</span>
<span id="130">130</span>
<span id="131">131</span>
<span id="132">132</span>
<span id="133">133</span>
<span id="134">134</span>
<span id="135">135</span>
<span id="136">136</span>
<span id="137">137</span>
<span id="138">138</span>
<span id="139">139</span>
<span id="140">140</span>
<span id="141">141</span>
<span id="142">142</span>
<span id="143">143</span>
<span id="144">144</span>
<span id="145">145</span>
<span id="146">146</span>
<span id="147">147</span>
<span id="148">148</span>
<span id="149">149</span>
<span id="150">150</span>
<span id="151">151</span>
<span id="152">152</span>
<span id="153">153</span>
<span id="154">154</span>
<span id="155">155</span>
<span id="156">156</span>
<span id="157">157</span>
<span id="158">158</span>
<span id="159">159</span>
<span id="160">160</span>
<span id="161">161</span>
<span id="162">162</span>
<span id="163">163</span>
<span id="164">164</span>
<span id="165">165</span>
<span id="166">166</span>
<span id="167">167</span>
<span id="168">168</span>
<span id="169">169</span>
<span id="170">170</span>
<span id="171">171</span>
<span id="172">172</span>
<span id="173">173</span>
<span id="174">174</span>
<span id="175">175</span>
<span id="176">176</span>
<span id="177">177</span>
<span id="178">178</span>
<span id="179">179</span>
<span id="180">180</span>
<span id="181">181</span>
<span id="182">182</span>
<span id="183">183</span>
<span id="184">184</span>
<span id="185">185</span>
<span id="186">186</span>
<span id="187">187</span>
<span id="188">188</span>
<span id="189">189</span>
<span id="190">190</span>
<span id="191">191</span>
<span id="192">192</span>
<span id="193">193</span>
<span id="194">194</span>
<span id="195">195</span>
<span id="196">196</span>
<span id="197">197</span>
<span id="198">198</span>
<span id="199">199</span>
<span id="200">200</span>
<span id="201">201</span>
<span id="202">202</span>
<span id="203">203</span>
<span id="204">204</span>
<span id="205">205</span>
<span id="206">206</span>
<span id="207">207</span>
<span id="208">208</span>
<span id="209">209</span>
<span id="210">210</span>
<span id="211">211</span>
<span id="212">212</span>
<span id="213">213</span>
<span id="214">214</span>
<span id="215">215</span>
<span id="216">216</span>
<span id="217">217</span>
<span id="218">218</span>
<span id="219">219</span>
<span id="220">220</span>
<span id="221">221</span>
<span id="222">222</span>
<span id="223">223</span>
<span id="224">224</span>
<span id="225">225</span>
<span id="226">226</span>
<span id="227">227</span>
<span id="228">228</span>
<span id="229">229</span>
<span id="230">230</span>
<span id="231">231</span>
<span id="232">232</span>
<span id="233">233</span>
<span id="234">234</span>
<span id="235">235</span>
<span id="236">236</span>
<span id="237">237</span>
<span id="238">238</span>
<span id="239">239</span>
<span id="240">240</span>
<span id="241">241</span>
<span id="242">242</span>
<span id="243">243</span>
<span id="244">244</span>
<span id="245">245</span>
<span id="246">246</span>
<span id="247">247</span>
<span id="248">248</span>
<span id="249">249</span>
<span id="250">250</span>
<span id="251">251</span>
<span id="252">252</span>
<span id="253">253</span>
<span id="254">254</span>
<span id="255">255</span>
<span id="256">256</span>
<span id="257">257</span>
<span id="258">258</span>
<span id="259">259</span>
<span id="260">260</span>
<span id="261">261</span>
<span id="262">262</span>
<span id="263">263</span>
<span id="264">264</span>
<span id="265">265</span>
<span id="266">266</span>
<span id="267">267</span>
<span id="268">268</span>
<span id="269">269</span>
<span id="270">270</span>
<span id="271">271</span>
<span id="272">272</span>
<span id="273">273</span>
<span id="274">274</span>
<span id="275">275</span>
<span id="276">276</span>
<span id="277">277</span>
<span id="278">278</span>
<span id="279">279</span>
<span id="280">280</span>
<span id="281">281</span>
<span id="282">282</span>
<span id="283">283</span>
<span id="284">284</span>
<span id="285">285</span>
<span id="286">286</span>
<span id="287">287</span>
<span id="288">288</span>
<span id="289">289</span>
<span id="290">290</span>
<span id="291">291</span>
<span id="292">292</span>
<span id="293">293</span>
<span id="294">294</span>
<span id="295">295</span>
<span id="296">296</span>
<span id="297">297</span>
<span id="298">298</span>
<span id="299">299</span>
<span id="300">300</span>
<span id="301">301</span>
<span id="302">302</span>
<span id="303">303</span>
<span id="304">304</span>
<span id="305">305</span>
<span id="306">306</span>
<span id="307">307</span>
<span id="308">308</span>
<span id="309">309</span>
<span id="310">310</span>
<span id="311">311</span>
<span id="312">312</span>
<span id="313">313</span>
<span id="314">314</span>
<span id="315">315</span>
<span id="316">316</span>
<span id="317">317</span>
<span id="318">318</span>
<span id="319">319</span>
<span id="320">320</span>
<span id="321">321</span>
<span id="322">322</span>
<span id="323">323</span>
<span id="324">324</span>
<span id="325">325</span>
<span id="326">326</span>
<span id="327">327</span>
<span id="328">328</span>
<span id="329">329</span>
<span id="330">330</span>
<span id="331">331</span>
<span id="332">332</span>
<span id="333">333</span>
<span id="334">334</span>
<span id="335">335</span>
<span id="336">336</span>
<span id="337">337</span>
<span id="338">338</span>
<span id="339">339</span>
<span id="340">340</span>
<span id="341">341</span>
<span id="342">342</span>
<span id="343">343</span>
<span id="344">344</span>
<span id="345">345</span>
<span id="346">346</span>
<span id="347">347</span>
<span id="348">348</span>
<span id="349">349</span>
<span id="350">350</span>
<span id="351">351</span>
<span id="352">352</span>
<span id="353">353</span>
<span id="354">354</span>
<span id="355">355</span>
<span id="356">356</span>
<span id="357">357</span>
<span id="358">358</span>
<span id="359">359</span>
<span id="360">360</span>
<span id="361">361</span>
<span id="362">362</span>
<span id="363">363</span>
<span id="364">364</span>
<span id="365">365</span>
<span id="366">366</span>
<span id="367">367</span>
<span id="368">368</span>
<span id="369">369</span>
<span id="370">370</span>
<span id="371">371</span>
<span id="372">372</span>
<span id="373">373</span>
<span id="374">374</span>
<span id="375">375</span>
<span id="376">376</span>
<span id="377">377</span>
<span id="378">378</span>
<span id="379">379</span>
<span id="380">380</span>
<span id="381">381</span>
<span id="382">382</span>
<span id="383">383</span>
<span id="384">384</span>
<span id="385">385</span>
<span id="386">386</span>
<span id="387">387</span>
<span id="388">388</span>
<span id="389">389</span>
<span id="390">390</span>
<span id="391">391</span>
<span id="392">392</span>
<span id="393">393</span>
<span id="394">394</span>
<span id="395">395</span>
<span id="396">396</span>
<span id="397">397</span>
<span id="398">398</span>
<span id="399">399</span>
<span id="400">400</span>
<span id="401">401</span>
<span id="402">402</span>
<span id="403">403</span>
<span id="404">404</span>
<span id="405">405</span>
<span id="406">406</span>
<span id="407">407</span>
<span id="408">408</span>
<span id="409">409</span>
<span id="410">410</span>
<span id="411">411</span>
<span id="412">412</span>
<span id="413">413</span>
<span id="414">414</span>
<span id="415">415</span>
<span id="416">416</span>
<span id="417">417</span>
<span id="418">418</span>
<span id="419">419</span>
<span id="420">420</span>
<span id="421">421</span>
<span id="422">422</span>
<span id="423">423</span>
<span id="424">424</span>
<span id="425">425</span>
<span id="426">426</span>
<span id="427">427</span>
<span id="428">428</span>
<span id="429">429</span>
<span id="430">430</span>
<span id="431">431</span>
<span id="432">432</span>
<span id="433">433</span>
<span id="434">434</span>
<span id="435">435</span>
<span id="436">436</span>
<span id="437">437</span>
<span id="438">438</span>
<span id="439">439</span>
<span id="440">440</span>
<span id="441">441</span>
<span id="442">442</span>
<span id="443">443</span>
<span id="444">444</span>
<span id="445">445</span>
<span id="446">446</span>
<span id="447">447</span>
<span id="448">448</span>
<span id="449">449</span>
<span id="450">450</span>
<span id="451">451</span>
<span id="452">452</span>
<span id="453">453</span>
<span id="454">454</span>
<span id="455">455</span>
<span id="456">456</span>
<span id="457">457</span>
<span id="458">458</span>
<span id="459">459</span>
<span id="460">460</span>
<span id="461">461</span>
<span id="462">462</span>
<span id="463">463</span>
<span id="464">464</span>
<span id="465">465</span>
<span id="466">466</span>
<span id="467">467</span>
<span id="468">468</span>
<span id="469">469</span>
<span id="470">470</span>
<span id="471">471</span>
<span id="472">472</span>
<span id="473">473</span>
<span id="474">474</span>
<span id="475">475</span>
<span id="476">476</span>
<span id="477">477</span>
<span id="478">478</span>
<span id="479">479</span>
<span id="480">480</span>
<span id="481">481</span>
<span id="482">482</span>
<span id="483">483</span>
<span id="484">484</span>
<span id="485">485</span>
<span id="486">486</span>
<span id="487">487</span>
<span id="488">488</span>
<span id="489">489</span>
<span id="490">490</span>
<span id="491">491</span>
<span id="492">492</span>
<span id="493">493</span>
<span id="494">494</span>
<span id="495">495</span>
<span id="496">496</span>
<span id="497">497</span>
<span id="498">498</span>
<span id="499">499</span>
<span id="500">500</span>
<span id="501">501</span>
<span id="502">502</span>
<span id="503">503</span>
<span id="504">504</span>
<span id="505">505</span>
<span id="506">506</span>
<span id="507">507</span>
<span id="508">508</span>
<span id="509">509</span>
<span id="510">510</span>
<span id="511">511</span>
<span id="512">512</span>
<span id="513">513</span>
<span id="514">514</span>
<span id="515">515</span>
<span id="516">516</span>
<span id="517">517</span>
<span id="518">518</span>
<span id="519">519</span>
<span id="520">520</span>
<span id="521">521</span>
<span id="522">522</span>
<span id="523">523</span>
<span id="524">524</span>
<span id="525">525</span>
<span id="526">526</span>
<span id="527">527</span>
<span id="528">528</span>
<span id="529">529</span>
<span id="530">530</span>
<span id="531">531</span>
<span id="532">532</span>
<span id="533">533</span>
<span id="534">534</span>
<span id="535">535</span>
<span id="536">536</span>
<span id="537">537</span>
<span id="538">538</span>
<span id="539">539</span>
<span id="540">540</span>
<span id="541">541</span>
<span id="542">542</span>
<span id="543">543</span>
<span id="544">544</span>
<span id="545">545</span>
<span id="546">546</span>
<span id="547">547</span>
<span id="548">548</span>
<span id="549">549</span>
<span id="550">550</span>
<span id="551">551</span>
<span id="552">552</span>
<span id="553">553</span>
<span id="554">554</span>
<span id="555">555</span>
<span id="556">556</span>
<span id="557">557</span>
<span id="558">558</span>
<span id="559">559</span>
<span id="560">560</span>
<span id="561">561</span>
<span id="562">562</span>
<span id="563">563</span>
<span id="564">564</span>
<span id="565">565</span>
<span id="566">566</span>
<span id="567">567</span>
<span id="568">568</span>
<span id="569">569</span>
<span id="570">570</span>
<span id="571">571</span>
<span id="572">572</span>
<span id="573">573</span>
<span id="574">574</span>
<span id="575">575</span>
<span id="576">576</span>
<span id="577">577</span>
</pre><pre class="rust"><code><span class="kw">use </span>matrix::{Matrix, MatrixSlice, BaseMatrix, BaseMatrixMut};
<span class="kw">use </span>vector::Vector;
<span class="kw">use </span>error::{Error, ErrorKind};
<span class="kw">use </span>matrix::decomposition::{
Decomposition,
HouseholderReflection,
HouseholderComposition
};
<span class="kw">use </span>matrix::decomposition::householder;
<span class="kw">use </span>std::any::Any;
<span class="kw">use </span>libnum::Float;
<span class="doccomment">/// The result of unpacking a QR decomposition.
///
/// Let `A` denote the `m x n` matrix given by `A = QR`.
/// Then `Q` is an `m x m` orthogonal matrix, and `R`
/// is an `m x n` upper trapezoidal matrix .
///
/// More precisely, if `m &gt; n`, then we have the decomposition
///
/// ```text
/// A = QR = Q [ R1 ]
/// [ 0 ]
/// ```
/// where `R1` is an `n x n` upper triangular matrix.
/// On the other hand, if `m &lt; n`, we have
///
/// ```text
/// A = QR = Q [ R1 R2 ]
/// ```
///
/// where `R1` is an `m x m` upper triangular matrix and
/// `R2` is an `m x (n - m)` general matrix.
///
/// To actually compute the QR decomposition, see
/// [Householder QR](struct.HouseholderQr.html).
</span><span class="attribute">#[derive(Debug, Clone)]
</span><span class="kw">pub struct </span>QR&lt;T&gt; {
<span class="doccomment">/// The orthogonal matrix `Q` in the decomposition `A = QR`.
</span><span class="kw">pub </span>q: Matrix&lt;T&gt;,
<span class="doccomment">/// The upper-trapezoidal matrix `R` in the decomposition `A = QR`.
</span><span class="kw">pub </span>r: Matrix&lt;T&gt;
}
<span class="doccomment">/// The result of computing a *thin* (or *reduced*) QR decomposition.
///
/// Let `A` denote the `m x n` matrix given by `A = QR`.
/// Then `Q` is an `m x m` orthogonal matrix, and `R`
/// is an `m x n` upper trapezoidal matrix.
///
/// If `m &gt; n`, we may write
///
/// ```text
/// A = QR = [ Q1 Q2 ] [ R1 ] = Q1 R1
/// [ 0 ]
/// ```
///
/// where `Q1` is an `m x n` matrix with orthogonal columns,
/// and `R1` is an `n x n` upper triangular matrix.
/// For some applications, the remaining (m - n) columns
/// of the full `Q` matrix are not needed, in which case
/// the thin QR decomposition is substantially cheaper if
/// `m &gt;&gt; n`.
///
/// If `m &lt;= n`, then the thin QR decomposition coincides with
/// the usual decomposition. See [QR](struct.QR.html) for details.
///
/// To actually compute the QR decomposition, see
/// [Householder QR](struct.HouseholderQr.html).
</span><span class="attribute">#[derive(Debug, Clone)]
</span><span class="kw">pub struct </span>ThinQR&lt;T&gt; {
<span class="doccomment">/// The matrix `Q1` in the decomposition `A = Q1 R1`.
</span><span class="kw">pub </span>q1: Matrix&lt;T&gt;,
<span class="doccomment">/// The upper-triangular matrix `R1` in the decomposition `A = Q1 R1`.
</span><span class="kw">pub </span>r1: Matrix&lt;T&gt;
}
<span class="doccomment">/// QR decomposition based on Householder reflections.
///
/// For any `m x n` matrix `A`, there exist an `m x m`
/// orthogonal matrix `Q` and an `m x n` upper trapezoidal
/// (triangular) matrix `R` such that
///
/// ```text
/// A = QR.
/// ```
///
/// `HouseholderQr` holds the result of a QR decomposition
/// procedure based on Householder reflections. The full
/// factors `Q` and `R` can be acquired by calling `unpack()`.
/// However, it turns out that the orthogonal factor `Q`
/// can be represented much more efficiently than as a
/// full `m x m` matrix. For this purpose, the [q()](#method.q)
/// method provides access to an instance of
/// [HouseholderComposition](struct.HouseholderComposition.html)
/// which allows the efficient application of the (implicit)
/// `Q` matrix.
///
/// For some applications, it is sufficient to compute a
/// *thin* (or *reduced*) QR decomposition. The thin QR decomposition
/// can be obtained by calling [unpack_thin()](#method.unpack_thin)
/// on the decomposition object.
///
/// # Examples
///
/// ```
/// # #[macro_use] extern crate rulinalg; fn main() {
/// use rulinalg::matrix::Matrix;
/// use rulinalg::matrix::decomposition::{
/// Decomposition, HouseholderQr, QR
/// };
///
/// let a = matrix![ 3.0, 2.0;
/// -5.0, 1.0;
/// 4.0, -2.0 ];
/// let identity = Matrix::identity(3);
///
/// let qr = HouseholderQr::decompose(a.clone());
/// let QR { q, r } = qr.unpack();
///
/// // Check that `Q` is orthogonal
/// assert_matrix_eq!(&amp;q * q.transpose(), identity, comp = float);
/// assert_matrix_eq!(q.transpose() * &amp;q, identity, comp = float);
///
/// // Check that `A = QR`
/// assert_matrix_eq!(q * r, a, comp = float);
/// # }
/// ```
///
/// # Internal storage format
/// Upon decomposition, the `HouseholderQr` struct takes ownership
/// of the matrix and repurposes its storage to compactly
/// store the factors `Q` and `R`.
/// In addition, a vector `tau` of size `min(m, n)`
/// holds auxiliary information about the Householder reflectors
/// which together constitute the `Q` matrix.
///
/// Specifically, given an input matrix `A`,
/// the upper triangular factor `R` is stored in `A_ij` for
/// `j &gt;= i`. The orthogonal factor `Q` is implicitly stored
/// as the composition of `p := min(m, n)` Householder reflectors
/// `Q_i`, such that
///
/// ```text
/// Q = Q_1 * Q_2 * ... * Q_p.
/// ```
///
/// Each such Householder reflection `Q_i` corresponds to a
/// transformation of the form (using MATLAB-like colon notation)
///
/// ```text
/// Q_i [1:(i-1), 1:(i-1)] = I
/// Q_i [i:m, i:m] = I - τ_i * v_i * transpose(v_i)
/// ```
///
/// where `I` denotes the identity matrix of appropriate size,
/// `v_i` is the *Householder vector* normalized in such a way that
/// its first element is implicitly `1` (and thus does not need to
/// be stored) and `τ_i` is an appropriate scale factor. Each vector
/// `v_i` has length `m - i + 1`, and since the first element does not
/// need to be stored, each `v_i` can be stored in column `i` of
/// the matrix `A`.
///
/// The scale factors `τ_i` are stored in a separate vector.
///
/// This storage scheme should be compatible with LAPACK, although
/// this has yet to be put to the test. For the same reason,
/// the internal storage is not exposed in the public API at this point.
</span><span class="attribute">#[derive(Debug, Clone)]
</span><span class="kw">pub struct </span>HouseholderQr&lt;T&gt; {
qr: Matrix&lt;T&gt;,
tau: Vec&lt;T&gt;
}
<span class="kw">impl</span>&lt;T&gt; HouseholderQr&lt;T&gt; <span class="kw">where </span>T: Float {
<span class="doccomment">/// Decomposes the given matrix into implicitly stored factors
/// `Q` and `R` as described in the struct documentation.
</span><span class="kw">pub fn </span>decompose(matrix: Matrix&lt;T&gt;) -&gt; HouseholderQr&lt;T&gt; {
<span class="kw">use </span>std::cmp::min;
<span class="comment">// The implementation here is based on
// Algorithm 5.2.1 (Householder QR) from
// Matrix Computations, 4th Ed,
// by Golub &amp; Van Loan
</span><span class="kw">let </span>m = matrix.rows();
<span class="kw">let </span>n = matrix.cols();
<span class="kw">let </span>p = min(m, n);
<span class="kw">let </span><span class="kw-2">mut </span>qr = matrix;
<span class="kw">let </span><span class="kw-2">mut </span>tau = <span class="macro">vec!</span>[T::zero(); p];
<span class="comment">// In order to avoid frequently allocating new vectors
// to hold the householder reflections, we allocate a single
// buffer which we can reuse for every iteration. We also
// need one as work space when applying the Householder
// transformations.
</span><span class="kw">let </span><span class="kw-2">mut </span>buffer = <span class="macro">vec!</span>[T::zero(); m];
<span class="kw">let </span><span class="kw-2">mut </span>multiply_buffer = <span class="macro">vec!</span>[T::zero(); n];
<span class="kw">for </span>j <span class="kw">in </span><span class="number">0 </span>.. p {
<span class="kw">let </span><span class="kw-2">mut </span>bottom_right = qr.sub_slice_mut([j, j], m - j, n - j);
<span class="comment">// The householder vector which we will hold in the buffer
// gets shorter for each iteration, so we truncate the buffer
// to the appropriate length.
</span>buffer.truncate(m - j);
multiply_buffer.truncate(bottom_right.cols());
bottom_right.col(<span class="number">0</span>).clone_into_slice(<span class="kw-2">&amp;mut </span>buffer);
<span class="kw">let </span>house = HouseholderReflection::compute(Vector::new(buffer));
house.buffered_left_multiply_into(<span class="kw-2">&amp;mut </span>bottom_right,
<span class="kw-2">&amp;mut </span>multiply_buffer);
house.store_in_col(<span class="kw-2">&amp;mut </span>bottom_right.col_mut(<span class="number">0</span>));
tau[j] = house.tau();
buffer = house.into_vector().into_vec();
}
HouseholderQr {
qr: qr,
tau: tau
}
}
<span class="doccomment">/// Returns the orthogonal factor `Q` as an instance of a
/// [HouseholderComposition](struct.HouseholderComposition.html)
/// operator.
</span><span class="kw">pub fn </span>q(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; HouseholderComposition&lt;T&gt; {
householder::create_composition(<span class="kw-2">&amp;</span><span class="self">self</span>.qr, <span class="kw-2">&amp;</span><span class="self">self</span>.tau)
}
<span class="doccomment">/// Computes the *thin* (or reduced) QR decomposition.
///
/// If `m &lt;= n`, the thin QR decomposition coincides with the
/// usual QR decomposition. See [ThinQR](struct.ThinQR.html)
/// for details.
///
/// # Examples
/// ```
/// # #[macro_use] extern crate rulinalg; fn main() {
/// # use rulinalg::matrix::Matrix;
/// # let x: Matrix&lt;f64&gt; = matrix![];
/// use rulinalg::matrix::decomposition::{HouseholderQr, ThinQR};
/// let x = matrix![3.0, 2.0;
/// 1.0, 2.0;
/// 4.0, 5.0];
/// let ThinQR { q1, r1 } = HouseholderQr::decompose(x).unpack_thin();
/// # }
/// ```
</span><span class="kw">pub fn </span>unpack_thin(<span class="self">self</span>) -&gt; ThinQR&lt;T&gt; {
<span class="comment">// Note: currently, there is no need to take ownership of
// `self`. However, it is actually possible to compute the
// rectangular Q1 factor in-place, but it is not currently
// done. By taking `self` now, we can make this change in
// the future without breaking changes.
</span><span class="kw">let </span>m = <span class="self">self</span>.qr.rows();
<span class="kw">let </span>n = <span class="self">self</span>.qr.cols();
<span class="kw">if </span>m &lt;= n {
<span class="comment">// If m &lt;= n, Thin QR coincides with regular QR
</span><span class="kw">let </span>qr = <span class="self">self</span>.unpack();
ThinQR {
q1: qr.q,
r1: qr.r
}
} <span class="kw">else </span>{
<span class="kw">let </span>composition = householder::create_composition(<span class="kw-2">&amp;</span><span class="self">self</span>.qr, <span class="kw-2">&amp;</span><span class="self">self</span>.tau);
<span class="kw">let </span>q1 = composition.first_k_columns(n);
<span class="kw">let </span>r1 = extract_r1(<span class="kw-2">&amp;</span><span class="self">self</span>.qr);
ThinQR {
q1: q1,
r1: r1
}
}
}
}
<span class="kw">impl</span>&lt;T: Float&gt; Decomposition <span class="kw">for </span>HouseholderQr&lt;T&gt; {
<span class="kw">type </span>Factors = QR&lt;T&gt;;
<span class="kw">fn </span>unpack(<span class="self">self</span>) -&gt; QR&lt;T&gt; {
<span class="kw">use </span>internal_utils;
<span class="kw">let </span>q = assemble_q(<span class="kw-2">&amp;</span><span class="self">self</span>.qr, <span class="kw-2">&amp;</span><span class="self">self</span>.tau);
<span class="kw">let </span><span class="kw-2">mut </span>r = <span class="self">self</span>.qr;
internal_utils::nullify_lower_triangular_part(<span class="kw-2">&amp;mut </span>r);
QR {
q: q,
r: r
}
}
}
<span class="kw">fn </span>assemble_q&lt;T: Float&gt;(qr: <span class="kw-2">&amp;</span>Matrix&lt;T&gt;, tau: <span class="kw-2">&amp;</span>Vec&lt;T&gt;) -&gt; Matrix&lt;T&gt; {
<span class="kw">let </span>m = qr.rows();
<span class="kw">let </span>q_operator = householder::create_composition(qr, tau);
q_operator.first_k_columns(m)
}
<span class="kw">fn </span>extract_r1&lt;T: Float&gt;(qr: <span class="kw-2">&amp;</span>Matrix&lt;T&gt;) -&gt; Matrix&lt;T&gt; {
<span class="kw">let </span>m = qr.rows();
<span class="kw">let </span>n = qr.cols();
<span class="kw">let </span><span class="kw-2">mut </span>data = Vec::&lt;T&gt;::with_capacity(m * n);
<span class="macro">assert!</span>(m &gt; n, <span class="string">&quot;We only want to extract r1 if m &gt; n!&quot;</span>);
<span class="kw">for </span>(i, row) <span class="kw">in </span>qr.row_iter().take(n).enumerate() {
<span class="kw">for _ in </span><span class="number">0 </span>.. i {
data.push(T::zero());
}
<span class="kw">for </span>element <span class="kw">in </span>row.raw_slice().iter().skip(i).cloned() {
data.push(element);
}
}
Matrix::new(n, n, data)
}
<span class="kw">impl</span>&lt;T&gt; Matrix&lt;T&gt;
<span class="kw">where </span>T: Any + Float
{
<span class="doccomment">/// Compute the QR decomposition of the matrix.
///
/// Returns the tuple (Q,R).
///
/// Note: this function is deprecated in favor of
/// [HouseholderQr](./decomposition/struct.HouseholderQr.html)
/// and will be removed in a future release.
///
/// # Examples
///
/// ```
/// # #[macro_use] extern crate rulinalg; fn main() {
/// use rulinalg::matrix::Matrix;
///
/// let m = matrix![1.0, 0.5, 0.5;
/// 0.5, 1.0, 0.5;
/// 0.5, 0.5, 1.0];
///
/// let (q, r) = m.qr_decomp().unwrap();
/// # }
/// ```
///
/// # Failures
///
/// - Cannot compute the QR decomposition.
</span><span class="attribute">#[deprecated]
</span><span class="kw">pub fn </span>qr_decomp(<span class="self">self</span>) -&gt; <span class="prelude-ty">Result</span>&lt;(Matrix&lt;T&gt;, Matrix&lt;T&gt;), Error&gt; {
<span class="kw">let </span>m = <span class="self">self</span>.rows();
<span class="kw">let </span>n = <span class="self">self</span>.cols();
<span class="kw">let </span><span class="kw-2">mut </span>q = Matrix::&lt;T&gt;::identity(m);
<span class="kw">let </span><span class="kw-2">mut </span>r = <span class="self">self</span>;
<span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..(n - ((m == n) <span class="kw">as </span>usize)) {
<span class="kw">let </span>holder_transform: <span class="prelude-ty">Result</span>&lt;Matrix&lt;T&gt;, Error&gt;;
{
<span class="kw">let </span>lower_slice = MatrixSlice::from_matrix(<span class="kw-2">&amp;</span>r, [i, i], m - i, <span class="number">1</span>);
holder_transform =
Matrix::make_householder(<span class="kw-2">&amp;</span>lower_slice.iter().cloned().collect::&lt;Vec&lt;<span class="kw">_</span>&gt;&gt;());
}
<span class="kw">if </span>!holder_transform.is_ok() {
<span class="kw">return </span><span class="prelude-val">Err</span>(Error::new(ErrorKind::DecompFailure,
<span class="string">&quot;Cannot compute QR decomposition.&quot;</span>));
} <span class="kw">else </span>{
<span class="kw">let </span><span class="kw-2">mut </span>holder_data = holder_transform.unwrap().into_vec();
<span class="comment">// This bit is inefficient
// using for now as we&#39;ll swap to lapack eventually.
</span><span class="kw">let </span><span class="kw-2">mut </span>h_full_data = Vec::with_capacity(m * m);
<span class="kw">for </span>j <span class="kw">in </span><span class="number">0</span>..m {
<span class="kw">let </span><span class="kw-2">mut </span>row_data: Vec&lt;T&gt;;
<span class="kw">if </span>j &lt; i {
row_data = <span class="macro">vec!</span>[T::zero(); m];
row_data[j] = T::one();
h_full_data.extend(row_data);
} <span class="kw">else </span>{
row_data = <span class="macro">vec!</span>[T::zero(); i];
h_full_data.extend(row_data);
h_full_data.extend(holder_data.drain(..m - i));
}
}
<span class="kw">let </span>h = Matrix::new(m, m, h_full_data);
q = q * <span class="kw-2">&amp;</span>h;
r = h * <span class="kw-2">&amp;</span>r;
}
}
<span class="prelude-val">Ok</span>((q, r))
}
}
<span class="attribute">#[cfg(test)]
</span><span class="kw">mod </span>tests {
<span class="kw">use </span><span class="kw">super</span>::HouseholderQr;
<span class="kw">use super</span>::{QR, ThinQR};
<span class="kw">use </span>matrix::{Matrix, BaseMatrix};
<span class="kw">use </span>matrix::decomposition::Decomposition;
<span class="kw">use </span>testsupport::is_upper_triangular;
<span class="kw">fn </span>verify_qr(x: Matrix&lt;f64&gt;, qr: QR&lt;f64&gt;) {
<span class="kw">let </span>m = x.rows();
<span class="kw">let </span>QR { <span class="kw-2">ref </span>q, <span class="kw-2">ref </span>r } = qr;
<span class="macro">assert_matrix_eq!</span>(q * r, x, comp = float, ulp = <span class="number">100</span>);
<span class="macro">assert!</span>(is_upper_triangular(r));
<span class="comment">// check orthogonality
</span><span class="macro">assert_matrix_eq!</span>(q.transpose() * q, Matrix::identity(m),
comp = float, ulp = <span class="number">100</span>);
<span class="macro">assert_matrix_eq!</span>(q * q.transpose(), Matrix::identity(m),
comp = float, ulp = <span class="number">100</span>);
}
<span class="kw">fn </span>verify_thin_qr(x: Matrix&lt;f64&gt;, qr: ThinQR&lt;f64&gt;) {
<span class="kw">use </span>std::cmp::min;
<span class="kw">let </span>m = x.rows();
<span class="kw">let </span>n = x.cols();
<span class="kw">let </span>ThinQR { <span class="kw-2">ref </span>q1, <span class="kw-2">ref </span>r1 } = qr;
<span class="macro">assert_matrix_eq!</span>(q1 * r1, x, comp = float, ulp = <span class="number">100</span>);
<span class="macro">assert!</span>(is_upper_triangular(r1));
<span class="comment">// Check that q1 has orthogonal columns
</span><span class="macro">assert_matrix_eq!</span>(q1.transpose() * q1, Matrix::identity(min(m, n)),
comp = float, ulp = <span class="number">100</span>);
}
<span class="attribute">#[test]
</span><span class="kw">pub fn </span>householder_qr_unpack_reconstruction() {
{
<span class="comment">// 1x1
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="comment">// 1x2
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="comment">// 2x1
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>;
<span class="number">2.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="comment">// 2x2
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>;
<span class="number">3.0</span>, <span class="number">4.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="comment">// 3x2
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>;
<span class="number">3.0</span>, <span class="number">4.0</span>;
<span class="number">4.0</span>, <span class="number">5.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="comment">// 2x3
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>, <span class="number">3.0</span>;
<span class="number">4.0</span>, <span class="number">5.0</span>, <span class="number">6.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="comment">// 3x3
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>, <span class="number">3.0</span>;
<span class="number">4.0</span>, <span class="number">5.0</span>, <span class="number">6.0</span>;
<span class="number">7.0</span>, <span class="number">8.0</span>, <span class="number">9.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
}
<span class="attribute">#[test]
</span><span class="kw">fn </span>householder_qr_unpack_square_reconstruction_corner_cases() {
{
<span class="kw">let </span>x = <span class="macro">matrix!</span>[-<span class="number">1.0</span>, <span class="number">0.0</span>;
<span class="number">0.0</span>, <span class="number">1.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">0.0</span>, <span class="number">0.0</span>;
<span class="number">0.0</span>, <span class="number">1.0</span>, <span class="number">0.0</span>;
<span class="number">0.0</span>, <span class="number">0.0</span>, -<span class="number">1.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
{
<span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">0.0</span>, <span class="number">0.0</span>;
<span class="number">0.0</span>, -<span class="number">1.0</span>, <span class="number">0.0</span>;
<span class="number">0.0</span>, <span class="number">0.0</span>, -<span class="number">1.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack();
verify_qr(x, qr);
}
}
<span class="attribute">#[test]
</span><span class="kw">fn </span>householder_qr_unpack_thin_reconstruction() {
{
<span class="comment">// 1x1
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack_thin();
verify_thin_qr(x, qr);
}
{
<span class="comment">// 1x2
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack_thin();
verify_thin_qr(x, qr);
}
{
<span class="comment">// 2x1
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>;
<span class="number">2.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack_thin();
verify_thin_qr(x, qr);
}
{
<span class="comment">// 2x2
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>;
<span class="number">3.0</span>, <span class="number">4.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack_thin();
verify_thin_qr(x, qr);
}
{
<span class="comment">// 3x2
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>;
<span class="number">3.0</span>, <span class="number">4.0</span>;
<span class="number">4.0</span>, <span class="number">5.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack_thin();
verify_thin_qr(x, qr);
}
{
<span class="comment">// 2x3
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>, <span class="number">3.0</span>;
<span class="number">4.0</span>, <span class="number">5.0</span>, <span class="number">6.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack_thin();
verify_thin_qr(x, qr);
}
{
<span class="comment">// 3x3
</span><span class="kw">let </span>x = <span class="macro">matrix!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>, <span class="number">3.0</span>;
<span class="number">4.0</span>, <span class="number">5.0</span>, <span class="number">6.0</span>;
<span class="number">7.0</span>, <span class="number">8.0</span>, <span class="number">9.0</span>];
<span class="kw">let </span>qr = HouseholderQr::decompose(x.clone()).unpack_thin();
verify_thin_qr(x, qr);
}
}
}
</code></pre></div>
</section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="rulinalg" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html>