private boolean[] computeSubset(final byte dummyValue, final long boardConfig) {
		final boolean[] tilesInSubset = new boolean[this.numOfTiles];
		for (int pos = this.numOfTiles - 1; pos >= 0; --pos) {
			final byte tile = (byte) ((boardConfig >> (pos << 2)) & 0xF);
			if (tile != dummyValue && tile != 0) {
				tilesInSubset[tile] = true;
			}
		}
		return tilesInSubset;
	}