Bad Pruning

[Onno Garms]

To improve the idea, and if SEE is available at that point, then try a combination of SEE and search with reduced depth. For example if SEE is bad then search this with a reduced depth as a verification, if it losses material or losses position value then prune/reduce.

Maybe worth a try, but I'm not sure if that would be an improvement. For example, moves leaving your queen in gardez have good see but should nevertheless be pruned.

[Onno Garms]

If I have understood correctly this is a kind of LMR launched on (beta - margin) instead of just beta....

This is not the way I viewed it, but maybe.

Note that I try bad pruning on all moves, not just late ones. Also depth reduction is much heavier and as you mentioned there is a margin.

[Onno Garms]

This is Multi-ProbCut. http://www.cs.ubc.ca/~jiang/papers/mpc_main.pdf

In deed. Thank you for pointing out.

Actually "bad pruning" is a special parametrization of Multi-ProbCut. I found my values by trial and error, without the statistical background of Multi-PropCut.

[uaf]

Interesting. I tried MPC several years ago in my engine Chiron but it never worked. I'll soon give your "bad pruning" algorithm a try.

How many points did Onno gain?

[Onno Garms]

How many points did Onno gain?

Code: Select all

Rank Name                     Elo    +    - games score oppo. draws 
   5 Onno 0-10-9-w             60   18   18  1040   59%    -6   31% 
   8 Onno 0-10-9               15   18   18  1040   53%    -6   33%

[Ferdy]

To improve the idea, and if SEE is available at that point, then try a combination of SEE and search with reduced depth. For example if SEE is bad then search this with a reduced depth as a verification, if it losses material or losses position value then prune/reduce.

Maybe worth a try, but I'm not sure if that would be an improvement. For example, moves leaving your queen in gardez have good see but should nevertheless be pruned.

Can you elaborate further on this,
"moves leaving your queen in gardez have good see"

[mcostalba]

Can you elaborate further on this,
"moves leaving your queen in gardez have good see"

It means moves that pin the queen.

[Ferdy]

Can you elaborate further on this,
"moves leaving your queen in gardez have good see"

It means moves that pin the queen.

Thanks, very aggressive prunning indeed, even a move with good see is pruned because of a bad result of a search to a reduced depth

[Onno Garms]

It means moves that pin the queen.

Not really. It means that when you opponent attacks your queen with say a rook, you should do something to escape that attack. ("Gardez" means that your queen is under attack as "check" means that your king is under attack.)

Take 1. e4 d5 2. ed Qd5 3. Nc3. SEE only considers the moving piece, so 3... Nf6 seems OK. In spite of good SEE 3...Nf6 is a very bad move because it leaves your queen in gardez. "bad pruning" will prune 3...Nf6

[mcostalba]

It means moves that pin the queen.

Not really. It means that when you opponent attacks your queen with say a rook, you should do something to escape that attack. ("Gardez" means that your queen is under attack as "check" means that your king is under attack.)

Take 1. e4 d5 2. ed Qd5 3. Nc3. SEE only considers the moving piece, so 3... Nf6 seems OK. In spite of good SEE 3...Nf6 is a very bad move because it leaves your queen in gardez. "bad pruning" will prune 3...Nf6

Yes, I meant this but I expressed with bad wording: pinning the queen is always SEE negative move if the attacking piece is not the opponent queen.