Yes, Theo, I think you might be right. I actually turned on game logging and re-ran the rollout. I noticed that GNU Backgammon really plays the bearin really really bad. Look at the attached games:
I just picked some games at random, and these two games really show awful playing. Can anyone explain what is going on? -Øystein On Wed, Sep 23, 2020 at 6:51 PM Theodore Hwa <[email protected]> wrote: > 2% seems more like the correct number. I think the first rollout is the > wrong one. > > A naive analysis: X looks virtually certain to get a piece off within 5 > rolls, which means that O has to win in 4 rolls for a gammon. Since O has > 13 pieces left, this means O has to roll doubles in 3 of the next 4 rolls, > which is about 4*(1/6)^3 ~ 1.85%. > > Ted > > On Wed, 23 Sep 2020, Øystein Schønning-Johansen wrote: > > > Hi all! > > I'm trying to rollout a position as cubeless moneygame. I think I see a > bug in GNU Backgammon. So > > here is my position: > > > > GNU Backgammon Position ID: 960BAMCw+0MAAA > > Match ID : cAkAAAAAAAAA > > +13-14-15-16-17-18------19-20-21-22-23-24-+ O: gnubg > > | | | O O O O O | O 0 points > > | | | O O O O | O > > | | | O O | > > | | | O | > > | | | O | > > v| |BAR| | (Cube: 1) > > | 7 | | | > > | X | | | > > | X | | X | > > | X | | X X X | On roll > > | X X | | X X X | 0 points > > +12-11-10--9--8--7-------6--5--4--3--2--1-+ X: oystein > > > > I strongly believe that this is a pretty simple position to play and I > think that X (on roll) will > > lose about 15% gammon. It should not be hard to roll this out. > > > > I generate this command file: > > > > [oystein@jupiter gnubg_cubeless_rollout_bug]$ cat rollout.cmd > > set rng mersenne > > new match 0 > > set turn 1 > > set board 960BAMCw+0MAAA > > set rollout trials 1296 > > set rollout cubeful off > > set rollout initial false > > set rollout quasirandom on > > set rollout truncation enable off > > set rollout bearofftruncation exact off > > set rollout bearofftruncation onesided off > > set rollout cubedecision plies 0 > > set rollout cubedecision cubeful off > > set rollout cubedecision prune off > > set rollout cubedecision noise 0 > > set rollout chequerplay plies 0 > > set rollout chequerplay cubeful off > > set rollout chequerplay prune off > > set rollout chequerplay noise 0 > > show rollout > > show board > > > > rollout > > > > I can then start this rollout with the command file as input. > > > > [oystein@jupiter gnubg_cubeless_rollout_bug]$ gnubg -t < rollout.cmd > > > > And the result becomes: > > > > Rollout done. Printing final results. > > > > Current Position: > > 0.000096 0.000000 0.000000 - 0.999904 0.147699 0.000000 CL -1.147507 > > [0.000008 0.000000 0.000000 - 0.000008 0.007830 0.000000 CL 0.007830] > 1r > > Full cubeless rollout with variance reduction > > 1296 games, Mersenne Twister dice gen. with seed 642205659 and > quasi-random dice > > Play: 0-ply cubeful > > Cube: 0-ply cubeful > > Time elapsed 2s Estimated time left 0s > > Estimated SE for "Current Position" after 1296 trials 0.007830 > > > > As seen, the rollout says 14.77% gammons. I can believe that! But now > comes the funny thing. Try the > > same thing but with checkerplay 2-ply. That mean changing one line in > the command file to read: > > > > set rollout chequerplay plies 2 > > > > And then run again. The new result is then: > > > > Rollout done. Printing final results. > > > > Current Position: > > 0.000098 0.000000 0.000000 - 0.999902 0.027877 0.000000 CL -1.027681 > > [0.000005 0.000000 0.000000 - 0.000005 0.011880 0.000000 CL 0.011726] > 1r > > Full cubeless rollout with variance reduction > > 1296 games, Mersenne Twister dice gen. with seed 642390699 and > quasi-random dice > > Play: 2-ply cubeless > > keep the first 0 0-ply moves and up to 5 more moves within equity 0.08 > > Skip pruning for 1-ply moves. > > Cube: 0-ply cubeful > > Time elapsed 1m21s Estimated time left 0s > > Estimated SE for "Current Position" after 1296 trials 0.011726 > > > > As seen here, the gammon losses are now only 2.79%. I do not believe > this result at all! Also look at > > the standard deviation of this value. Could it be that the number is > wrong due to a missing > > initialisation or something? > > > > Please help me investigate. > > > > -Øystein > > > >
logfile-0001140-a.sgf
Description: application/go-sgf
logfile-0000137-a.sgf
Description: application/go-sgf
