need help with search instability

[DrRibosome]

Are there any standard ways for dealing with search instability?

It seems like entries in the hash from previous searches somehow confuse the search, causing it to pick moves that it never would pick if I were to start the engine in that position with a cleared hash. This does not seem to be a huge problem (ie, it probably happens once every few games at most), but occasionally it picks very bad moves because of it. I know I could clear the hash, etc, before searching again, but I want to take advantage of the previously searched positions in the hash.

[syzygy]

but occasionally it picks very bad moves because of it.

If your hash contains "very bad moves", you have a bug or you do something 'wrong'.

Just a guess. You should only store a move that improves alpha or fails high. In nodes where all moves fail low, you should keep the move that was previously stored for that position, if any.

[hgm]

This does not sound like 'search instability', but like a plain hash bug.

[PK]

typical hash bug is saving stuff when time is out - been there, seen that, got a queen for free when playing against my first engine.