@Override
    public double unsafe_get(int row, int col) {
        if( row == 0 ) {
            if( col == 0 ) {
                return a11;
            } else if( col == 1 ) {
                return a12;
            }
        } else if( row == 1 ) {
            if( col == 0 ) {
                return a21;
            } else if( col == 1 ) {
                return a22;
            }
        }
        throw new IllegalArgumentException("Row and/or column out of range. "+row+" "+col);
    }