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Rollout and Comments

Posted By: eXtreme Gammon
Date: Tuesday, 1 December 2009, at 12:09 a.m.

In Response To: Hit or not (eXtreme Gammon)

Here is the rollout

is Player 2 score: 2 pip: 68

5 point match

pip: 53 score: 2 is Player 1

XGID=-DBCBaB-B----------bbcbcb-:1:-1:1:21:2:2:0:5:10

to play 21

1.	Rollout1	8/5*	eq: +0.263
	Player: Opponent: 66.40% (G:0.66% B:0.01%) 33.60% (G:4.56% B:0.15%) Conf: ± 0.001 (+0.262...+0.264) Duration: 4 minutes 14 seconds
2.	Rollout1	4/2 3/2	eq: +0.246 (-0.017)
	Player: Opponent: 68.25% (G:0.07% B:0.00%) 31.75% (G:0.10% B:0.00%) Conf: ± 0.001 (+0.245...+0.247) Duration: 1 minute 54 seconds
3.	XG Roller+	4/1	eq: +0.215 (-0.048)
	Player: Opponent: 67.55% (G:0.09% B:0.00%) 32.45% (G:0.12% B:0.00%)
4.	XG Roller+	3/2 3/1	eq: +0.206 (-0.057)
	Player: Opponent: 67.11% (G:0.07% B:0.00%) 32.89% (G:0.18% B:0.00%)
5.	3 ply	4/3 4/2	eq: +0.203 (-0.060)
	Player: Opponent: 67.18% (G:0.07% B:0.00%) 32.82% (G:0.15% B:0.00%)
1 10368 Games rolled with Variance Reduction. Moves and cube decisions: 4 ply

eXtreme Gammon Version: 1.10, MET: eXtremeGammon

Phil's question was : "You win fewer games, you lose a lot more gammons, and you only win a tiny bit more gammons. How can the hit be correct?????

My answer: "By hitting you basically void any redouble ability of the opponent. 8/5* which is 0.290 cubeless become only 0.267 cubeful. So holding the cube is worth only 0.023. For 4/2 3/2 cubeless=0.359 cubeful=0.246 so the cube worth 0.113, almost 5 times more.

The idea is that when you hit your opponent will almost never redouble (if he hits he’ll play for the gammon, and if he misses you’ll clear the blot and have a huge race advance (you're about 95% favorite) ).

If you don’t hit you are basically in a race. The opponent will have the ability to redouble very often. The cubeful equity of 0.246 is equivalent to 37.7% wins as there are no gammons (-0.246+1)/2=0.377. The cubeless Winning percentage shows 31.7% chances to win. So in that position holding the cube give the opponent 6.0% more chance to win the game.

Compare that to the your opponent 33.6% winning chances (and 4.6% gammon) if you hit: You actually lose 4.1% more game by not hitting. With a gammon price of 0.502 (XG MET) it is worth to take the risk.

Note that it’s a posteriori analyze. There is no way I would have made that analyze over the board."

Like Daniel Murphy pointed the source of the problem is comparing Cubeless winning chances to Cubeful equities. Just a quick note: You can see the cubeless equity by moving the mouse over the move.

Messages In This Thread

• Hit or not
  eXtreme Gammon -- Monday, 30 November 2009, at 1:53 a.m.
  • Hit or not
    Stick -- Monday, 30 November 2009, at 2:02 a.m.
    • Hit or not
      neilkaz -- Monday, 30 November 2009, at 3:51 a.m.
      • Hit or not
        Phil Simborg -- Monday, 30 November 2009, at 5:13 a.m.
        • Hit or not
          Matt Cohn-Geier -- Monday, 30 November 2009, at 5:51 a.m.
        • Hit or not
          Daniel Murphy -- Monday, 30 November 2009, at 7:19 a.m.
  • Hit or not
    Matt Cohn-Geier -- Monday, 30 November 2009, at 2:03 a.m.
    • Hit or not
      eXtreme Gammon -- Monday, 30 November 2009, at 2:33 a.m.
      • Hit or not
        lenny -- Monday, 30 November 2009, at 2:40 a.m.
        • Hit or not
          Stick -- Monday, 30 November 2009, at 3:41 a.m.
        • Hit or not
          Stick -- Monday, 30 November 2009, at 4:39 a.m.
  • Hit or not
    Bill Riles -- Monday, 30 November 2009, at 3:10 a.m.
  • Hit or not
    John O'Hagan -- Monday, 30 November 2009, at 3:47 a.m.
  • Hit or not
    Rich Munitz -- Monday, 30 November 2009, at 5:09 a.m.
  • Hit or not
    garyo -- Monday, 30 November 2009, at 4:45 p.m.
  • Rollout and Comments
    eXtreme Gammon -- Tuesday, 1 December 2009, at 12:09 a.m.
    • Rollout and Comments (money)
      eXtreme Gammon -- Tuesday, 1 December 2009, at 12:12 a.m.
    • Rollout and Comments
      Phil Simborg -- Tuesday, 1 December 2009, at 7:28 a.m.
  • Hit or not
    Timothy Chow -- Tuesday, 1 December 2009, at 9:25 p.m.
    • Hit or not
      eXtreme Gammon -- Wednesday, 2 December 2009, at 3:13 a.m.
    • Hit or not
      Daniel Murphy -- Wednesday, 2 December 2009, at 6:41 a.m.