code: private static void checkKhatriRaoArguments(Matrix A, Matrix B) {
          if (A.numColumns() != B.numColumns())
              throw new IndexOutOfBoundsException(
                      "A.numColumns != B.numColumns (" + A.numColumns() + " != "
                              + B.numColumns() + ")");
      }
docs: Tests if the matrices have an equal number of columns.
  
  @param A
  @param B