title: Math.js is slow to multiply 2 big matrices
body: <p>I'm trying to speed-up matrices multiplications in pure javascript. Multiplications appear to be very slow above a few hundreds of lines, over the minute on a thousand of lines: you'll see the execution time bellow.</p>
  
  <p>How would you solve this? We are working on a split + parallelization solution in Node.js so I'm looking for the best options to optimize it in pure javascript. My solution has to adapt the parallelized flows itself to the number of CPU threads available (that is unknown at design time).</p>
  
  <p>Some data :
  </p>
  
  <pre><code>const math = require("mathjs");
  
  // a1 is a 1000x1000 float matrix
  // b1 is a 1000x400
  math.multiply(a1, b1)
  // runs in 19.6 seconds on a CPU 4.2Ghz
  
  // a2 is 1600x1200
  // b2 is 1200x800
  math.multiply(a2, b2)
  // runs in 78 seconds
  </code></pre>