Eigen Matrices multiplication
<p>Why is it necessary to use the noallias() expression when doing matrix product when using c++ eigen library?</p>

<pre><code>m1.noalias() += (s1*s2*conj(s3)*s4) * m2.adjoint() * m3.conjugate()
</code></pre>

<p>I have been reading some notes about it but still find it difficult to understand.</p>