I mentioned running it twice in my last post, and it reminded me that I've been meaning to post on the subject.
First, a "running it twice" refresher: when two players are all in with cards to come in a cash game, they can agree to run it twice: deal out two sets of the remaining cards to come. A player must win on both boards to win the hand. If each player wins on one board, the pot is chopped.
For or against? We never run it twice at WNP or the Surreal lunch game, but it's an acceptable practice if both players agree, and an interesting variance reducer. I keep trying to remember to offer it up in an all in situation with cards to come, but I always seem to forget in the moment.
I'm no mathematician, but the EV on the hand supposedly doesn't change much if at all, it just dramatically reduces the variance. So, if two players are all in and it's A @ 50% vs. B @50%, without running it twice, A will win all the chips 50% of the time, and B will win all the chips 50% of the time. If they run it twice, A will win all the chips 10% of the time, B will win all the chips 10% of the time, and they will chop the pot 80% of the time.
That's a made-up simplification to convey the point that EV is maintained, but short-term variance is reduced, and a chop becomes likely. The EV of these situations is maintained even when it's more like 90% vs. 10% or whatever.
I am generally in favor of running it twice if I could just remember to offer, but the metagame question is: does knowing that someone is for or against running it twice change how you play a hand against them? Perhaps players are more willing to make a "bold" all-in semi-bluff against a player they know will run it twice if they are called...