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| From: | Ian Shaw |
| Subject: | RE: Interesting question/experiment about value of cube ownership |
| Date: | Mon, 4 Mar 2024 12:26:52 +0000 |
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Sorry, MK, I didn't read back over the old threads, to see what links you had referenced, before I replied. It was late at night, and I was using my phone rather than a PC. In that case, I must have misunderstood what you meant by, "Is making the bot auto-play the same as doing rollouts?" It seemed to me that, since only you know what’s in your scripts, it was most likely that you were asking about rollouts
are, although that also seemed unlikely. You asked earlier about the GNUBG ID I used. It was: 4HPwATDgc/ABMA:cAkAAAAAAAAA This is the ID obtained after the sequence I suggested: 4HPwATDgc/ABMA:cAkAAAAAAAAA (Thanks for the link to the BKGM post. I’d forgotten about it, but fortunately it had recently been discussed on Daily Gammon, where someone else also found your 4-roll solution!)
They are identical, so there is no indication in the ID to indicate whether it is the opening roll. Therefore, the evaluation is the same. The Contact Net does not have an input for Opening Roll, which makes sense. The bot plays by maximizing
the equity of the next position. The opening layout – with doubles prohibited - is never the next position. Comparing evaluation, Rollout as Normal Position, Rollout as Initial Position, we can see that the evaluation is close to the value of the rollout. The rollout as the initial position is lower since it doesn’t include those useful doubles.
I don’t think the value of 0.36 ppg for cube ownership that we both obtained is a "coincidence". I think it's evidence that your script is a good emulation of a rollout. If you think 0.36 is inaccurate, I’m open to persuasion. Do you
have a theory as to why it’s wrong, or what you think the correct value is? Regarding the equity at the beginning of the game, I’m not aware of any “age-old fallacy”. It's well established that winning the opening roll confers an advantage. I don’t think there's any theory that says the equity (between equal
opponents) is non-zero before the opening roll. Indeed, the construction of most match equity tables is based on the equity at the start of the game being zero (unless they are assuming unequal players). Finally, please lay off the disparagement. “What will it take for you guys to give some credit/benefit of the doubt to others than just yourselves?” is unnecessary. I’m not sure which group of ‘guys’ you lump me into; I’m just a gnubg
user and a moderate player. I give lots of credit to loads of people who have contributed far more to backgammon than I ever will.
Ian --Original Message----- From: MK <playbg-rgb@yahoo.com>
Sent: Monday, March 4, 2024 3:17 AM To: Ian Shaw <Ian.Shaw@riverauto.co.uk>;
bug-gnubg@gnu.org Cc: Philippe Michel <philippe.michel7@free.fr> Subject: Re: Interesting question/experiment about value of cube ownership On 3/1/2024 6:02 PM, Ian Shaw wrote: > "Is making the bot auto-play the > same as doing rollouts?" > > It sounds like you are asking what a rollout is? I wasn't. >
https://www.gnu.org/software/gnubg/manual/html_node/Introduction-to-ro > llouts.html I had read it many a times before. > https://www.bkgm.com/openings/rollouts.html This is funny. You are referring me back to the same link that I had given in my reply to you on February 10, here in this very same thread... :) What will it take for you guys to give some credit/benefit of the doubt to others than
just yourselves? > Your auto-play script sounds very similar but I don't know exactly
> what it does. Fair enough. My explaining in my previous post about what it does in this specific experiment was probably too brief and not very clear. > The main difference would be that you can make your scripts double
> using your own algorithm. Yes, in some experiment I did that but not in this one. > Or indeed, veer from the bot's best chequer play. I haven't done any checker experiments yet but I may. > Minor differences might be the play settings for search depth and
> pruning. Okay. You now made me realize that even unchecking all of the optional settings in roll-outs, it will not be the same as bot auto-playing. We both must have come up with the same 0.36 ppg by coincidence. Regardless, I believe that it's
inaccurate in either case anyway. > Try this manual sequence, and evaluate the next move. > This gets you back to the start position. But doubles would be
> allowed, so the bot evaluation should not be the same as that of the
> opening roll. > 64: 13/7 24/20 > 33: 24/18* 13/7 > 21: bar/24 20/18* > 51: bar/24 18/13 > 32: 18/13 Ah, it's getting interesting. GnuBG doesn't know the difference between the initial and recycled "starting position". XG does but wrongly, backwards. Snowie did but adjusted it by the wrong amount. I first wrote about this problem with XG in response to a related discussion in RGB, on Dec 26, 2022. See: https://groups.google.com/g/rec.games.backgammon/c/RgcdohfwyYs/m/NtnrIaUTCAAJ Then I checked the same problem in Gnubg and I posted about it on the same day. See: https://groups.google.com/g/rec.games.backgammon/c/QU1jM9aatO0/m/EBkivQ3vBQAJ The next day after that, I checked it in Snowie and I posted a comprehensive recap about the subject. See: This is a very important issue regarding the ages-old fallacy that the equity at the start of the game, i.e. the equity of the starting position, is zero. It's not! Anyone who really cares about the accuracy of bots' equity calculations should make time to read the above three threads or at least the first article in each, because miscalculating the equity of the opening moves ripple through the following moves, causing them all to be wrong even
if slightly but also compoundingly depending on which bot does what how... Incidentally, in the third thread above, you'll find a link to one of my only two posts that ever appeared on BKGM, this one being about the shortest possible moves to recycle to the starting position. See: https://www.bkgm.com/rgb/rgb.cgi?view+68 My 4-rolls solution allowed doubles and I had explained later in RBG that it would be legal not only if initial doubles are allowed in some variants but also when we recycled to the starting position more than once. See: https://groups.google.com/g/rec.games.backgammon/c/8vUhA8fpEN0/m/nXMtpFOrmFoJ So, yes, I was the one who not only didn't assume you could recycle only once but also tested the three bots to see if/how they would treat the starting position if it occurred multiple times. I guess I just like to not stop until I
get to the bottom of things... MK |
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