[TUHS] cubic (was: unix v4 tape found)

[Ken Thompson via TUHS]

patasnik said he solved cubit as a forced win for
the first player. he submitted it to
elwyn berlekamp for verification and publication.
patasnik had solved it by hand up to a point
where a computer could make forcing moves
to a win.

elwyn asked me to verify the solution.
i did -- it was a win. a by-product was a program
that would find forced wins. from there a
program was easy.

i haven't thought about this since then.
thank you for bringing it up.


On Thu, Dec 25, 2025 at 7:54 PM Adam Thornton via TUHS <tuhs at tuhs.org>
wrote:

> Thank you for the excellent Christmas gift!
>
> On Thu, Dec 25, 2025 at 8:44 PM Jonathan Gray <jsg at jsg.id.au> wrote:
>
> > On Sat, Dec 20, 2025 at 05:17:35PM -0700, Adam Thornton via TUHS wrote:
> > > "cubic" exists both here and on the v7 I have.  There don't seem to be
> > > sources, though, at least not in the obvious places.
> > >
> > > I went looking online, and didn't find much besides Patashnik's 1980
> > paper
> > > (the acknowledgements there are a lovely rogues' gallery of exactly
> who'd
> > > you'd expect).
> > >
> > > I think (based on the oral history interview) that cubic here is
> > probably a
> > > Ken program.
> >
> > "Some of the things Ken wrote on the PDP-7 by 1969 include
> > ...
> > A graphical-interface 3D tic-tac-toe program (4x4x4) run with the light
> > pen."
> > https://www.nokia.com/bell-labs/about/dennis-m-ritchie/ken-games.html
> >
> > "His early work has been on MULTICS, file system design and simulation,
> > computer chess, cubic (3D) tic-tac-toe, and language implementation."
> > K Thompson, The Unix Command Language, 1976
> > https://archive.org/details/theunixcommandlanguage
> >
> > >
> > > I was playing with it, but trying to keep the board state in my head
> > rather
> > > than on paper (which was a mistake) and was intrigued by the fact that
> it
> > > found a forced loss for me and laid it out for me.
> > >
> > > My question is, do the sources to "cubic" exist anywhere?
> > >
> > > Adam
> >
> > https://github.com/DoctorWkt/pdp7-unix/blob/master/src/cmd/ttt1.s
> >         jms messg; i>;040;w>;i>;n>;0
> > https://github.com/DoctorWkt/pdp7-unix/blob/master/src/cmd/ttt2.s
> >
> > tuhs Applications/Dennis_Tapes/dmr_tapes.tgz
> > games/ttt-play/
> > games/ttt-solve/
> > contain .s files with '3d tic-tac-toe' comments
> >
> > 'I have a force win' is in
> > games/ttt-play/ot1.s
> >
>