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JellyFish 2.0 Release

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Fredrik Dahl

Feb 21, 1996, 3:00:00 AM2/21/96
JellyFish 2.0 is due for release Feb 29.

It comes in three different variants:
Player ( 50 US$)
Tutor (110 $)
Analyzer (250 $)

The Player is equal to the Tutor, except for lack of
evaluations and comments. It is not copy protected.
The Tutor and Analyzer are still copy protected in the same way as before.
It does not do any funny tricks to the hard drive, only requires the
user to run a confirmation program from the original diskette once a month.

Upgrade prices:
Tutor 1.x -> Tutor 2.0 : 40$
Analyzer 1.x -> Analyzer 2.0 : 80$
Tutor 1.x -> Analyzer 2.0 : 160$
For upgrading within the 2.0 series we give full value for previous purchase.

The original diskette one is upgrading from MUST be returned.

Some of the improvements in the program:

-Level 7 with simplified double lookahead (3-ply play)
Playable on a pentium, useful for analysis on a 486.
-Bearoff databases
-Improved cube action
-Powerful variance reduction for lookahead rollouts
-Powerful variance reduction for human rollouts
(Normally reduces the number of games needed for a given
error tolerance by a factor in the 5-50 range, creates no bias)
-JellyFish' checker movement has adjustable blink and delay
-Takeback function that rewinds the game
-Printing of games/matches/positions
-List of top n plays with evaluation/verification
and more...

Order from:
EFFECT Software A/S
Brugata 1
N-0186 OSLO
phone +47 22 17 71 90
fax +47 22 17 05 42

Please use International Postal Money Order, Masterscard or Visa.
If you use Mastrescard or Visa, send the account number, date of expiration,
amount and signature. You may send it by fax.

You may also send a check, but in that case
please add 10$ for expenses.

Hardware requirements:
386sx (486 dx preferable for full value)
Software requirements:
Windows 3.1
The JellyFish programs come on 3.5" diskettes.

Fredrik Dahl.

Andrew Paik

Feb 22, 1996, 3:00:00 AM2/22/96
Hi Fredrik,

> JellyFish 2.0 is due for release Feb 29.

> It comes in three different variants:
> Player ( 50 US$)
> Tutor (110 $)
> Analyzer (250 $)

What is the difference between the 3 versions? Do they all play the same
quaility game? You mentioned that the player is the same as the tutor, but
without comments and evaluations. What kind of comments does it make? If
the tutor does evaluations, what is it that the Analyzer does?


Michael J Zehr

Mar 1, 1996, 3:00:00 AM3/1/96
In article <4h5j5m$> (Dave Biggs) writes:
>In article <4gk0jg$>, (Fredrik Dahl) says:
>>In the Tutor you can have positions evaluated with equity and
>>the 6 probabilities.
>Dumb newbie type questions...what do you mean by equity & 6 probabilities?
>I've seen both mentioned in the periodical "Inside Backgammon".
>And what do you mean by "rollouts"?

Equity is used in several slightly different ways all generally meaning
the value of a position to a particular side. Here's an example of the
most common meaning:

Suppose I have two checkers on my two point, you have two checkers on
your ace point, and I'm on roll. If I roll any 1 except 11, I bear my
two checkers off and win the value of the cube. Otherwise, you roll and
bear two checkers off and I lose. I win 26/36 times and lose 10/36
times. What I expect to win is (26-10)/36 or 16/36. Thus my equity is
16/36 or .444.

Suppose I am considering doubling. If I double and you take, I win just
as many games but for twice the value, so my equity becomes .889. Since
I increase my equity by doubling, I want to double.

Should you take or not? If you drop, you lose the game all the time and
your equity is -1.00. If you take, your equity is -.889. Since this is
an improvement, you take.

Some important observations:

Equity depends on the cube position. If the cube is in the center or I
own it, my equity in this position is .889, otherwise it's .444. In
more complicated positions, my equity by doubling is less than twice the
equity by not doubling because the opponent gets some value out of being
able to redouble.

Opponents have equal and opposite equity. (This must be true because
anything one side loses, the other side wins.)

In this sense of the word, equity is being used to describe the value of
a position assuming perfect play by both sides.

Rollouts are used when a position is more complicated than being able to
simply list the winning rolls for one side. A rollout is playing the
game to completion over and over and over and keeping track of the
number of points won or lost by a side. The existence of computer
programs that are good enough to do a reliable rollout has greatly
increased our understanding of the game in recent years. Rollouts by
hand are a great way to understand a position, but are necessarily much
slower. For a serious backgammon student, the rollout featuer of
JellyFish is an important study aid.

"6 probabilities" -- I believe this refers to the chance of winning a
single game, a gammon, or a backgammon, and the chance of losing the
same. This gives greater detail than simply the equity of a position.

For example, you can have an equity of .50 by winning a gammon .5 times
and losing a single game the rest of the time (.5*2 - .5 = .5) or by
winning a single game .75 times and losing a single game .25 times (.75
- .25 = .5). When looking at a position for a match, gammons and
backgammons are not always worth twice and thrice a normal game. (For
example, at double match point, one of the two positions mentioned above
is much better!)

Other uses of equity:

Sometimes it's used to compare the relative strengths of players rather
than a specific position assuming perfect play by both sides. For
example, I might say that my equity against some other opponent is +.1,
i.e. I expect to win .1 points per game I play that person. (This
represents a fairly wide gap in skills, and I would be very happy to
play this person for money of course! <grin>) On the other hand, my
equity against Kit Woolsey might be -.05 pts per game.

"Equity surge" -- You can say this when you've just gotten a great roll.
Your equity suddenly went up.

I hope these explanations helped. You can also look for the Backgammon
FAQ (posted here periodically or available through anoymous ftp at

-michael j zehr

Dave Biggs

Mar 1, 1996, 3:00:00 AM3/1/96
In article <4gk0jg$>, (Fredrik Dahl) says:

>The 3 play the same game.

>In the Tutor you can have positions evaluated with equity and

>the 6 probabilities. It can also give a list of top choices
>for a given dice roll or comment when it dislikes you play or comment
>on your cube action. (All can be turned off.)
>The Analyzer in addition supports rollouts of different types,
>with the new in this version being rollouts played with lookahead (level 6)
>and user controled ones (both with a very powerful variance reduction
>method usually reducing the number of games needed by a factor 5-50).

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