docs: public static void setMatrix(final double[][] m1, final int r0, final int r1, final int c0, final int c1, final double[][] m2) {
      assert r0 <= r1 && c0 <= c1 : ERR_INVALID_RANGE;
      assert r1 <= m1.length && c1 <= m1[0].length : ERR_MATRIX_DIMENSIONS;
      final int coldim = c1 - c0;
      for(int i = r0; i < r1; i++) {
        System.arraycopy(m2[i - r0], 0, m1[i], c0, coldim);
      }
    }