Bad Pruning

[Cardoso]

Hi,
just a couple of questions:

We do bad pruning before or after null move?

If it's before is it a good idea to not do null move if bad prunning failed to prune?

If it's after null move and this didn't return a value, is it sound to still do bad prunning?

Is it sound to do null move in a bad prunning search/tree?
Is it sound to do bad prunning in a null move search/tree?

best regards,
alvaro

[Don]

Hi,
just a couple of questions:

We do bad pruning before or after null move?

Null move IS pruning. And we do other kinds of pruning too, generally after we try the null move to get a cutoff.

If it's before is it a good idea to not do null move if bad prunning failed to prune?

If it's after null move and this didn't return a value, is it sound to still do bad prunning?

Is it sound to do null move in a bad prunning search/tree?
Is it sound to do bad prunning in a null move search/tree?

Define "bad pruning", do you mean bad decisions or pruning of bad moves? Pruning is often about the alpha/beta window, not always the quality of the move.

best regards,
alvaro

The top programs do very heavy pruning and every program is going to prune sometimes when it should not. Also, every program is going to NOT prune when it should. The trick is finding the right balance to make the right decision as often as possible and that the bad decisions are not too bad. It's very easy to make a program not miss as much by simply doing things like you suggest, not pruning when you might to avoid making a mistake - but the relevant question is whether it makes the program stronger or not.

If the only pruning you do is null move pruning, you will have a very weak program.

[Cardoso]

Hi,
just a couple of questions:

We do bad pruning before or after null move?

Null move IS pruning. And we do other kinds of pruning too, generally after we try the null move to get a cutoff.

If it's before is it a good idea to not do null move if bad prunning failed to prune?

If it's after null move and this didn't return a value, is it sound to still do bad prunning?

Is it sound to do null move in a bad prunning search/tree?
Is it sound to do bad prunning in a null move search/tree?

Define "bad pruning", do you mean bad decisions or pruning of bad moves? Pruning is often about the alpha/beta window, not always the quality of the move.

best regards,
alvaro

The top programs do very heavy pruning and every program is going to prune sometimes when it should not. Also, every program is going to NOT prune when it should. The trick is finding the right balance to make the right decision as often as possible and that the bad decisions are not too bad. It's very easy to make a program not miss as much by simply doing things like you suggest, not pruning when you might to avoid making a mistake - but the relevant question is whether it makes the program stronger or not.

If the only pruning you do is null move pruning, you will have a very weak program.

thanks Don, but I was talking in the following context:

http://talkchess.com/forum/viewtopic.ph ... 07&start=0

best regards,
Alvaro