<p>In <a href="https://github.com/mlpack/mlpack/pull/749#discussion_r76078363">src/mlpack/methods/lsh/lshmodel_impl.hpp</a>:</p>
<pre style='color:#555'>&gt; +  maxKValue = k;
&gt; +
&gt; +  // Save pointer to training set.
&gt; +  this-&gt;referenceSet = &amp;referenceSet;
&gt; +
&gt; +  // Step 1. Select a random sample of the dataset. We will work with only that
&gt; +  // sample.
&gt; +  arma::vec sampleHelper(referenceSet.n_cols, arma::fill::randu);
&gt; +
&gt; +  // Keep a sample of the dataset: We have uniformly random numbers in [0, 1],
&gt; +  // so we expect about N*sampleRate of them to be in [0, sampleRate).
&gt; +  arma::mat sampleSet = referenceSet.cols(
&gt; +        arma::find(sampleHelper &lt; sampleRate));
&gt; +  // Shuffle to be impartial (in case dataset is sorted in some way).
&gt; +  sampleSet = arma::shuffle(sampleSet);
&gt; +  const size_t numSamples = sampleSet.n_cols; // Points in sampled set.
</pre>
<p>I think I wrote my comment without thoroughly looking at the code; I see now that it's sampling without replacement.  Thanks for the explanation.  In that case <code>ObtainDistinctSamples()</code> should do what you need, I think.</p>

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