Part 2 Take or Pass:

from: Christian Liebe-Harkort

As an example we will look at position 594, you are white and have to decide, whether you should take or pass.

In a regular money game this is an easy take.

For our analysis we will make the same assumptions as in Part 1:

  • you play $10 a point
  • the rake is 5%, with the winner paying 10%
  • At least $80 are at the table

Position 594, Category Bear Off

Roll or Double?

Black vs White

Moneygame: Jacoby and Beaver

added at 3/7/2010 10:22 AM, from admin

Pipcount: 4(0) - 4(0)

Comment:
Two very effective doubles make this a take.

Evaluation Level: 7 ply

Winning Chances:

Player: 79.94%79.94%0.00%0.00%
Opponent: 20.06%20.06%0.00%0.00%

Cubeful Equities:

No Double:+0.599-0.352
Double / Take:+0.951best
Double / Drop:+1.000+0.049

Best Cube Action: Double / Take

Cubeless Equities:

No Double:+0.599
Double:+1.198

Software: eXtreme Gammon Version: 1.12

Calculations without rake

Let's start with the equity for a take when there is no rake:

cube

1st roll

2nd roll

payout

$/point

total

4

26

36

-100%

$10

-$37.440.00

8

10

26

100%

$10

$20.800.00

8

10

10

-100%

$10

-$8.000.00

sum

-$24.640.00

equity

-$19.01

Your equity is $-19.01, exactly the value, the software displays (+0.951 x -2 x $10)

That means, on average you would loose $19.01 by taking in this position. Your alternative is to pass the 4 cube and that means losing two points, $10 each, for a total of $20.

Taking saves you $0.99 on average and is the correct decision.

Calculations with rake

Now we do the same calculation, with the difference that your payout is just 90% (100% - 10% rake).

cube

1st roll

2nd roll

payout

$/point

total

4

26

36

-100%

$10

-$37.440.00

8

10

26

90%

$10

$18.720.00

8

10

10

-100%

$10

-$8.000.00

sum

-$26.720.00

equity

-$20.62

Your equity for taking is $-20.62.

That means that on average you would loose $20.62 if you take in this position. Once more, your alternative is to pass the 4 cube and that means losing two points, $10 each, for a total of $20.

Taking costs you $0.62 on average and is a mistake (eg:-0.031).

Rake adjusted Take point:

The basic take point of 25% in money games is calculated as follows:

You compare the equities for pass versus take. If you are doubled to 2 you can either pass, losing one point on average or take. The equity for the take is calculated qas follows: Let "p" be the chance that you win. Then the chance that you don't win is 1-p. So your equity is:

2p - 2 x  (1-p) this can be reduced to 2p -2 + 2p or 4p - 2

So we can take when 4p - 2 > - 1 (= the one point we lose when we pass)  , that transforms to 4p > 1 or p > ¼ or p > 25%

Please note this formula does not take into account that you could redouble, so this calculation is only valid for a dead cube.

No we do the same calculation, but introduce the new variable "r" that is the rake in percent. So as the winner pays for both players instead of 1 point he will receive only 1-2r points. We still lose one point when we pass, but when we take our calculation looks different:

2p x (1-2r) - 2 x (1-p) = 2p -4pr -2 + 2p = 4p - 4pr - 2

So we should take when 4p - 4pr - 2 > -1 or 4p - 4pr > 1 or p (4 - 4r) > 1 or

p  > 1/(4-4r) or p > ¼(1-r)

The following table will give you an idea on how the rake affects the take point.

rake

take point

0.0%

25.0%

1.0%

25.3%

2.0%

25.5%

3.0%

25.8%

4.0%

26.0%

5.0%

26.3%

6.0%

26.6%

7.0%

26.9%

8.0%

27.2%

9.0%

27.5%

10.0%

27.8%

11.0%

28.1%

12.0%

28.4%

13.0%

28.7%

14.0%

29.1%

15.0%

29.4%

16.0%

29.8%

17.0%

30.1%

18.0%

30.5%

19.0%

30.9%

20.0%

31.3%

21.0%

31.6%

22.0%

32.1%

23.0%

32.5%

24.0%

32.9%

25.0%

33.3%

When you pay rake, your take point is a higher than in a regular money game. The higher the rake, the higher is your take point. As a general guideline: In close decisions between taking and passing, you should tend towards passing.

updated: Thursday, April 15, 2010