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[Martin Sedlak]

As for futility: never had problem with that and seems pretty stable.
Futility simply prunes (ignores) certain moves at nodes where eval+margin is below beta in scout search.
In general:
-never do futility when evading a check
-don't skip potentially good/dangerous moves: hashmove, captures, promotions, castling, checks, killers and in general any moves you want to extend
perhaps good history moves shouldn't be skipped as well but i don't do that in cheng; i also don't prune passer pushes

PS hashmove, captures, castling and killers boil down to "do futility after the killers phase in movegen"