easy move?

Discussion of chess software programming and technical issues.

Moderators: bob, hgm, Harvey Williamson

Forum rules
This textbox is used to restore diagrams posted with the [d] tag before the upgrade.
Robert Pope
Posts: 510
Joined: Sat Mar 25, 2006 7:27 pm

Re: easy move?

Post by Robert Pope » Fri Oct 19, 2018 8:45 pm

hgm wrote:
Fri Oct 19, 2018 6:20 pm
I guess one of the reasons people think that easy move is not worth it is that they only test in ponder-off games. Spending a lot of time on an easy move in a ponder-on game is giving the opponent free thinking time on a guaranteed ponder hit. Of course some variants have more easy moves than others.

In Shokidoki I consider a move easy if there is at least a 300cP gap between its score and that of the second-best move, in all iterations.
I think it's more a concern that the effort to save time/shorten opponents ponder-time will end up being at the cost of a blunder.

Ras
Posts: 1159
Joined: Tue Aug 30, 2016 6:19 pm
Contact:

Re: easy move?

Post by Ras » Sat Oct 20, 2018 12:53 am

Robert Pope wrote:
Fri Oct 19, 2018 8:45 pm
I think it's more a concern that the effort to save time/shorten opponents ponder-time will end up being at the cost of a blunder.
This is especially likely when the situation is just to good to be true. That's why I check back whether the result of the move is within the overall range from the last move turn. If it's just like +300 centipawns out of nowhere, this looks suspicious and is worth regular investigation. It's not trivial to have that check for a UCI engine, but it's still possible to verify whether the current position is a continuous game.

If it isn't a continuation so that there is no valid last move turn score, then better drop any "easy move" approach except if it's the only legal move.
Rasmus Althoff
https://www.ct800.net

User avatar
hgm
Posts: 23718
Joined: Fri Mar 10, 2006 9:06 am
Location: Amsterdam
Full name: H G Muller
Contact:

Re: easy move?

Post by hgm » Sat Oct 20, 2018 6:44 am

Robert Pope wrote:
Fri Oct 19, 2018 8:45 pm
I think it's more a concern that the effort to save time/shorten opponents ponder-time will end up being at the cost of a blunder.
You can say exactly the same thing for any reduction in the search. Yet we know that reductions pay off, and that a fixed-depth search is crap. Because compared to a search with reductions, the fixed-depth search with the same number of nodes effectively reduces the important branches rather than the crappy ones.

If you can recapture a Queen in only one way after QxQ, it would be extremely foolhardy to keep thinking and thinking after at d=1 you already found NxQ as best move, just on the off chance that in this case it might be better not to recapture that Queen, and play on with a Queen down.

Point is that you always have limited resources, and that allocating more resources to any particular sub-problem, although always better for that sub-problem, will always go at the expense of deteriorating the situation in other sub-problem. When you would consider the shortened thinking time in case of an easy move the norm, so that you have a large supply of 'spare' time to allocate to improve on your play compared to that faster TC, that extra time would be best spent thinking about positions where there is a high chance to actually change the move choice for the better. Positions where you are a Queen down will hardly ever turn into positions where you are ahead. And if the only move that keeps you about equal at low depth turns out to lose more than a Queen at high depth, your only hope is that the opponent will not see it, as he will certainly preserve the advantage of a Queen when you do not recapture, even in the 1-ply iteration. Giving him extra (ponder) time in that situation is really the worst thing you could do.

odomobo
Posts: 59
Joined: Thu Jul 05, 2018 11:09 pm
Location: Chicago, IL
Full name: Josh Odom

Re: easy move?

Post by odomobo » Mon Oct 22, 2018 3:32 pm

There's also more discussion on this topic in this thread: http://talkchess.com/forum3/viewtopic.php?f=7&t=67944

Post Reply