NZColumns&#8203;(<a href="MatrixBlock.html" title="class in org.apache.sysds.runtime.matrix.data">MatrixBlock</a>&nbsp;in,
                                            int&nbsp;k,
                                            <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/concurrent/ExecutorService.html?is-external=true" title="class or interface in java.util.concurrent" class="externalLink">ExecutorService</a>&nbsp;pool)
                                     throws <a href="htt