public Block[][] SplitChanneal(byte[][] _graph, int _y, int _x)
    {
        if((_x % 8 != 0) || (_y % 8 != 0)){
            System.err.println("[ERROR] Input data should begins on a multiple of 8!");
            return null;
        }

        // number of blocks
        int _yBlock = _y/8;
        int _xBlock = _x/8;

        Block[][] _blocks = new Block[_yBlock][_xBlock];

        for(int i=0; i<_y; i+=8)
            for (int j = 0; j < _x; j+=8) {
                _blocks[i/8][j/8] = new Block(_graph, i, j);
            }

        return _blocks;
    }