The 0ply sees a sure win for O with no gammons, and plays a random move basically.
Let's hope the race net can be improved once again :) (maybe you can check previous nets to see if that was always the case ...) -Joseph On Thu, 24 Sep 2020 at 06:51, Øystein Schønning-Johansen <[email protected]> wrote: > 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 >> > >> > > >
