docs: public static void setMatrix(final double[][] m1, final int[] r, final int[] c, final double[][] m2) {
      for(int i = 0; i < r.length; i++) {
        final double[] row1 = m1[r[i]], row2 = m2[i];
        for(int j = 0; j < c.length; j++) {
          row1[c[j]] = row2[j];
        }
      }
    }