Make Eigen run in a Multi-Thread
<p>I have some questions regarding Eigen parallelization.</p>

<p>To my understanding, Eigen handles its internal parallelization but I want to activate multi threading. I just started compiling with G++ using the flag "-fopenmp" and running my executable with OMP_NUM_THREADS=4 ./exec. </p>

<p>Some parts of the code that run only using C++ code I used:</p>

<pre><code>#pragma omp parallel
{
}
</code></pre>

<p>Looking at my system monitor I can see that sometimes I used more than one thread, but most of the time it isn't. I don't know if I have to use additional OpenMp code. </p>

<p>In the following link:</p>

<p><a href="https://eigen.tuxfamily.org/dox/TopicMultiThreading.html" rel="nofollow">https://eigen.tuxfamily.org/dox/TopicMultiThreading.html</a></p>

<p>They mention that "in the case your application is parallelized with OpenMP, you might want to disable Eigen's own parallization as detailed in the previous section", but I don't really understand if I have to or how to do it.</p>

<p>I hope I am not mixing concepts here.</p>

<p>My thanks in advance. </p>