Starcraft AI blog

I learned a new trick from watching the ASL 11 games. The game was Sharp versus Best, the second game of group B in the round of 16. Watch with English commentary by Nyoken and Scan on Afreeca or on Youtube. On the Afreeca vod, the game starts a little after 55 minutes in. The Youtube vod was trimmed and it starts closer to 46 minutes.

Sharp scouted Best’s base with an SCV, which then left the base. Best blocked the entrance to his main with a zealot to prevent further scouting. But when the SCV returned for a second look, it mineral-walked through Best’s blocking zealot and got a look around anyway. I was surprised, and Nyoken (who knows more about Starcraft than I do) was also surprised: How did the SCV get vision of Best’s minerals to do the mineral walk? Sharp had no apparent way to see the minerals.

Scan explained it. The SCV was click-moved to a location far from the base (a location chosen so that the second-scout timing would come out right). As it was leaving, while it still had vision of the minerals, Sharp shift-clicked back to the minerals. That was the last time Sharp had the necessary vision. The SCV followed its orders to move far away, then followed the queued order to mineral walk back into the base. I had never seen it before.

I sometimes see bots using queued commands to move units across the map through waypoints. (In BWAPI you do that by setting the optional shiftQueueCommand parameter of a command to true; it defaults to false.) It is usually a mistake. When you queue a move command, the moving unit completes the command by coming to a stop at the destination before the next command in the queue executes. It adds a delay—a very visible delay. If you’re following waypoints, it is normally better to issue a new move command in real time before the unit reaches the waypoint, so that it never slows down or stops, and reaches its final destination sooner. But in the case of mineral walk, you may not still have vision of the minerals later when it’s time to issue that command. If you want to issue a sequence of moves ending with a mineral walk, you may want to queue them all while you still have vision. It will execute later whether you have vision then or not.

I tried it myself, and it works. What a complicated game!

It’s been a while since my last post, but I’m still working, however slowly.

In today’s SSCAIT report “By the skin of your teeth”, the last game of the broadcast is the same game I analyzed last month, Chobo-Steamhammer on Python, the corsair-reaver game, with commentary by the player himself. His analysis of the game seems similar to mine, except of course with insight into the human player’s thoughts rather than the machine’s.

AIST S4 results are published. Despite my optimism, Steamhammer scored 0-2 in its first match then 0-2 in the loser’s bracket to be the first knocked out, as in the past. In fact, it is the worst result ever; in its other two tries, Steamhammer scored 1-4 rather than 0-4 as here.

Here are the results in crosstable form, counting games, players in rank order. The tournament counted matches, not games, so you can’t directly read off the tournament results from here. But it may give a different perspective.

#	bot	overall	star	purp	will	drag	bana	stea
1	stardust	7-2		5-1	*	*	2-1	*
2	purplewave	7-6	1-5		4-0	2-1	*	*
3	willyt	4-5	*	0-4		2-1	*	2-0
4	dragon	4-5	*	1-2	1-2		2-1	*
5	bananabrain	4-4	1-2	*	*	1-2		2-0
6	steamhammer	0-4	*	*	0-2	*	0-2

I watched the replays. PurpleWave 2-1 Dragon after Dragon crashed twice; the first game was a convincing win by Dragon. Again versus WillyT, Dragon won once and crashed twice. PurpleWave tried to counter Stardust with reavers, but suffered when bottlenecked at ramps. If you want the best games, I recommend the ones named in the replay pack Series 2, G1, and Series 10, G1.