[bb-puzzles] Re: several messages

[Carl D. <de...@ma...>]

On Tue, 20 Mar 2001, Doug Edmunds wrote:
> The 'Minor Confusion' puzzle is a one-pivot puzzle (a 'zebra'-type
> puzzle).

I do not understand this concept of "pivot".  Rather than explaining it,
you could help me out by directing me to a puzzle on your web site that is
NOT a one-pivot puzzle.

> I had not indicated that that within each group, the values were
> different: that each name's variable was different from
> each other, each position was different, etc. (hand coding would be A ## D,
> A ## G, ...).

That is what I call the SDR constraint: System of Distinct
Representatives.  My program only handles problems with that constraint.
However, with a vast number of examples, I show that many problems that
are not initially in SDR form can be put into SDR by the addition of a few
dummy variables.  So I would like see if I can take what you consider to
be a multi-pivot puzzle and convert to a one-pivot problem.

Is the terminology "pivot" standard?  If so, I'll have to use it in my
paper.


> Eclipse has the 'alldifferent' function, used thus:
>
> alldifferent([A,D,G,J,R,S]),
> alldifferent([BI,CH,DI,LE,ST,TI]),
> alldifferent([CF,FB,PI,RF,SS,TB]),
> alldifferent([BA,FO,MA,NO,PE,TR]),
> alldifferent([CA,EE,GR,NA,PU,TO]),

Identical to the 'Distinct' operator in my program.

> I added those 5 lines to my code (copy attached) and the solution time
> dropped from 12+ seconds to <.5 seconds, which is close to the time
> needed just to load the file. I will be uploading the new file to the
> website soon.

Eclipse is a compiled language, right?  I guess then that my solution time
of 3 seconds in the huge, lumbering, interpretted system Maple is pretty
good.  I can do the zebra puzzle in .5 seconds.  (All times are on an AMD
K6 600 MHz or on a Sparc Ultra 1).

That Eclipse time is to find the feasible solution AND prove it unique,
right?

That you for the references; I will check them out.

I will send you my program and numerous very detailed examples of its use
if you want.