ecified as option of the sfCluster call (and not using argument <code>cpus</code>). 
If another cluster solution (specified by argument <code>clustertype</code>) shall be used, a cluster with <code>cpus</code> CPUs is started if <code>parallel=TRUE</code>. <code>parallel=FALSE</code> switches back to sequential execution. See Details.</p></td>
    </tr>
    <tr>
      <th>cpus</th>
      <td><p>number of nodes, i.e., number of parallel running R processes, to be set up in a cluster, if not specified by comm