<p>It's an Armadillo versioning issue with this line:</p>
<pre><code>double const max = arma::abs(input.row(k)).max();
</code></pre>
<p>Try <code>arma::max(arma::abs(input.row(k)))</code>. I'm not sure in what version the <code>.max()</code> function was added to arbitrary expressions, but either way both of those expressions should compile to the same thing, and the <code>arma::max()</code> version should compile on older Armadillo versions. (I'll be bumping the minimum Armadillo required version to 4.200 or so soon, I just haven't gotten around to it yet.)</p>
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