title: How to set spark to use a specific number of cores?
body: <p>I have 3 machines, each machine with 12 cores. How I can set spark to use the 12 cores?</p>
  
  <p>In the spark-env.sh Im already setting the memory, but I dont find how to set the number of cores. Can you give a help?</p>
  
  <pre><code>export SPARK_WORKER_MEMORY=28G
  </code></pre>