Author: buildbot
Date: Sat Feb 4 00:48:54 2017
New Revision: 1006183
Log:
Staging update by buildbot for mahout
Modified:
websites/staging/mahout/trunk/content/ (props changed)
websites/staging/mahout/trunk/content/users/algorithms/d-spca.html
Propchange: websites/staging/mahout/trunk/content/
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Modified: websites/staging/mahout/trunk/content/users/algorithms/d-spca.html
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dt:hover > .elementid-permalink { visibility: visible }</style>
<h1 id="distributed-stochastic-pca">Distributed Stochastic PCA<a
class="headerlink" href="#distributed-stochastic-pca" title="Permanent
link">¶</a></h1>
<h2 id="intro">Intro<a class="headerlink" href="#intro" title="Permanent
link">¶</a></h2>
-<p>Mahout has a distributed implementation of Stochastic PCA[1]. This
algorithm computes the exact equivalent of Mahout's
dssvd(<code>\(\mathbf{A-1\mu}\)</code>) by modifying the <code>dssvd</code>
algorithm so as to avoid forming <code>\(\mathbf{A-1\mu}\)</code>, which would
densify a sparse input. Thus, it is suitable for work with both dense and
sparse inputs.</p>
+<p>Mahout has a distributed implementation of Stochastic PCA[1]. This
algorithm computes the exact equivalent of Mahout's
dssvd(<code>\(\mathbf{A-1\mu^\top}\)</code>) by modifying the
<code>dssvd</code> algorithm so as to avoid forming
<code>\(\mathbf{A-1\mu^\top}\)</code>, which would densify a sparse input.
Thus, it is suitable for work with both dense and sparse inputs.</p>
<h2 id="algorithm">Algorithm<a class="headerlink" href="#algorithm"
title="Permanent link">¶</a></h2>
<p>Given an <em>m</em> <code>\(\times\)</code> <em>n</em> matrix
<code>\(\mathbf{A}\)</code>, a target rank <em>k</em>, and an oversampling
parameter <em>p</em>, this procedure computes a <em>k</em>-rank PCA by finding
the unknowns in <code>\(\mathbf{Aâ1\mu^\top \approx U\Sigma
V^\top}\)</code>:</p>
<ol>