capturing PV in QSearch

[sandermvdb]

Yesterday I implemented Bruce's code and I am also writing the PV back to the hash. But what do you mean by this regarding Stockfish: 'but with values that will cause the entry to be ignored for cutoffs'?
And you are updating your "always" hash only if the score is better. But what do you mean by better?

i only overwrite the "always replace" half of the TT entry, not the "deeper then" part. if you already have an entry in the "deeper then" entry, you wouldn't want to overwrite it with a entry that has no depth; just use the one that is there. if you do store the PV, you want to make sure the depth and value are not such that the TT would think the entry is good enough to cause a cutoff, so put in a negative depth which will never be better than the depth you are in the search (unless your search allows negative depths). i didn't say i use the score, i write back a score that represents a value that can never occur in the evaluation. it doesn't matter, actually since the negative depth prevents the entry from ever being used for a score, but it will still return the move.

You are saying that a PV value doesn't have any depth?? It sounds logic to me that if you searched till depth 10, the 3rd PV-move should be stored in the TT with a depth of 7 as an EXACT value.