<p>Hello. I have a mlpack program dealing with products of large matrices ~(100000,400). <br>
Repeated executions started giving me different results and I have written a few lines example to illustrate such problem: </p>

<p>#include <br>
using namespace arma;</p>

<p>int main(void) { <br>
//Vector declaration &amp; initialisation<br>
     vec a_vector=ones(400);<br>
     vec fcol=ones(61);<br>
     mat M = ones(400,61);<br>
     for (int iter=0; iter&lt;1; iter++){<br>
     a_vector=M<em>fcol;<br>
     }<br>
std::cout &lt;&lt; "i.rows=" &lt;&lt; a_vector.n_rows &lt;&lt; " i.cols=" &lt;&lt; a_vector.n_cols &lt;&lt; " i399=" &lt;&lt; a_vector(399);<br>
if (a_vector(399)!=61) std::cout &lt;&lt; "</em>" &lt;&lt; std::endl;<br>
else std::cout &lt;&lt; std::endl;<br>
return 0;<br>
}</p>

<p>Here we find a simple matrix multiplication of matrix * column to obtain a column-&gt; (400,61)*(61,1)=(400,1). <br>
To check whether this method works I print out the last element of the resulting column. Since all elements are set to 1, any final element should be a sum of 61 elements = 61. <br>
Well, it turns out that when running it several times these doesn't always hold. </p>

<p>You can try with a .sh script that runs, say, 80 times. <br>
This problem is not encountered when using only armadillo. </p>

<p>The program was compiled through:<br>
"g++ main.cpp -O2 -std=gnu++11 -I/home/usrname/lib/Boost161/include -L/home/usrname/lib/Boost161/lib -larmadillo -lmlpack -I/home/usrname/lib/mlpacklib/include -L/home/usrname/lib/mlpacklib/lib"  </p>

<p>I would be really grateful if someone could shed some light on this. <br>
<a href="https://github.com/mlpack/mlpack/files/408636/code.zip">code.zip</a></p>

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