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Backgammon => Backgammon problems => Topic started by: blitzxz on March 08, 2008, 12:21:12 PM

Poll
Question: Checker play?
Option 1: 24/23* 6/4*
Option 2: 24/23* 24/22
Option 3: 24/22 6/5
Option 4: 24/23* 13/11
Title: Middle game strategy
Post by: blitzxz on March 08, 2008, 12:21:12 PM
GNU Backgammon  Position ID: sn3AASLgHHwAOQ
                 Match ID   : cAmlAAAAAAAA
+13-14-15-16-17-18------19-20-21-22-23-24-+     O: Opponent
| X                |   | O  O  O  X  O  X |     0 points
| X                |   | O  O  O        X |     
| X                |   | O              X |     
| X                |   | O                |     
| X                |   | O                |   
v|                  |BAR|                  |     5 point match (Cube: 1)
|                  |   |                  |   
|                  |   |                  |     
| O           X    |   | X                |     
| O           X    |   | X                |     Rolled 21
| O           X    |   | X     O        O |     0 points
+12-11-10--9--8--7-------6--5--4--3--2--1-+     X: You

Pip count:
You 201
Opponent 134

Spoiler
General rule is that don't seek backgames but sometimes that's the best option. Here Black has lost the opening hitting contest but can continue hit like crazy but he also has to build board and run at the same time.  Chances for doing all that when white has strong board are slim. In couple of rolls white is propably going to get big double.

Instead black should go to 3-1 backgame which is one of the strongest back games. Black has very nice timing and white has only 3 point prime. This is perfect time to switch to backgame strategy. It's so strong that white can't even double for a long time. Any hitting play here is a huge blunder (which I of course made also).

Here is the rollout of 3 best moves. Double hit loses almost half a point.


    1. Rollout          24/22 6/5                    Eq.:  -0,318
       0,485 0,060 0,003 - 0,515 0,288 0,057 CL  -0,344 CF  -0,318
      [0,006 0,003 0,001 - 0,006 0,005 0,004 CL   0,017 CF   0,041]
        Full cubeful rollout with var.redn.
        531 games, Mersenne Twister dice gen. with seed 1056721625 and quasi-random dice
        Play: world class 2-ply cubeful prune [world class]
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,16
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune [world class]
    2. Rollout          24/22 8/7                    Eq.:  -0,364 ( -0,046)
       0,479 0,053 0,004 - 0,521 0,291 0,055 CL  -0,373 CF  -0,364
      [0,005 0,003 0,001 - 0,005 0,005 0,006 CL   0,016 CF   0,035]
        Full cubeful rollout with var.redn.
        531 games, Mersenne Twister dice gen. with seed 1056721625 and quasi-random dice
        Play: world class 2-ply cubeful prune [world class]
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,16
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune [world class]
    3. Rollout          24/23* 24/22                 Eq.:  -0,536 ( -0,218)
       0,416 0,075 0,004 - 0,584 0,280 0,021 CL  -0,429 CF  -0,536
      [0,004 0,003 0,001 - 0,004 0,006 0,003 CL   0,015 CF   0,032]
        Full cubeful rollout with var.redn.
        530 games, Mersenne Twister dice gen. with seed 1056721625 and quasi-random dice
        Play: world class 2-ply cubeful prune [world class]
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,16
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune [world class]
[close]
Title: Re: Middle game strategy
Post by: PersianLord on March 09, 2008, 06:10:15 AM
Very nice position. I chose the wrong choice and thought that hitting is better. Great lesson anyway.  :thumbsup:

But why backgames are to be avoided? I think that when behind in the race, playing backgame is very effective. Isn't it?
Title: Re: Middle game strategy
Post by: Hardy_whv on March 09, 2008, 06:33:36 AM
Quote from: PersianLord on March 09, 2008, 06:10:15 AM
But why backgames are to be avoided? I think that when behind in the race, playing backgame is very effective. Isn't it?

If there is no alternative to playing a backgame, a backgame has to be played. However, if you don't win that game, you are very likely to lose a Gammon (or even Backgammon), because you are far behind in the race. And: You need good timing, i.e. you have to be quite far behind in the race, to play a backgame effectively. Otherwise, your homeboard (or prime), which is your last way of winning the game, if you finally hit the opponent, will crunch. Doubles can be especially harmful, when playing a backgame, because they can ruin your timing.

So backgames provide quite a good probability to win the game, but if you don't win, you probably lose a gammon. That's the bad thing when playing backgames.

Hardy  B)
Title: Re: Middle game strategy
Post by: PersianLord on March 09, 2008, 03:28:31 PM
Quote from: Hardy_whv on March 09, 2008, 06:33:36 AM
If there is no alternative to playing a backgame, a backgame has to be played. However, if you don't win that game, you are very likely to lose a Gammon (or even Backgammon), because you are far behind in the race. And: You need good timing, i.e. you have to be quite far behind in the race, to play a backgame effectively. Otherwise, your homeboard (or prime), which is your last way of winning the game, if you finally hit the opponent, will crunch. Doubles can be especially harmful, when playing a backgame, because they can ruin your timing.

So backgames provide quite a good probability to win the game, but if you don't win, you probably lose a gammon. That's the bad thing when playing backgames.

Hardy  B)

Well said, Hardy  :thumbsup:

I agree with you that one must be very cautious in applying backgame as the gammon loss is likely if things go wrong.

Regards
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