MTD-f: Extracting PV ?

[Henk]

Perhaps using alpha beta search is better than PVS for there you have a similar problem with search inconsistencies.

There is no inconsistency problem in PVS - if the re-search disagrees with the scout search, you trust the re-search and move on. The only question is whether it overall saves you time or not (and if it doesn't you have problems to be looking at).

But if may be that scout search erroneously gives a fail low (because of other heuristic pruning) and the research is not performed. That means it skips a potential good move. This may happen less frequently when using alpha beta search.

[bob]

Perhaps using alpha beta search is better than PVS for there you have a similar problem with search inconsistencies.

There is no inconsistency problem in PVS - if the re-search disagrees with the scout search, you trust the re-search and move on. The only question is whether it overall saves you time or not (and if it doesn't you have problems to be looking at).

But if may be that scout search erroneously gives a fail low (because of other heuristic pruning) and the research is not performed. That means it skips a potential good move. This may happen less frequently when using alpha beta search.

You are always re-searching in MTD(f). If you fail low, the basic idea is to re-search with a lowered null-window.