We have expressions from both Bill Raymond and Tom Holroyd on this
question. That's good to see, because I've wondered whether you two guys
were acquainted with each other. I thought you should be.
I really need to analyze the Woods (and FcPro) solver's method of
expression. I was surprised to discover only very recently that it does in
fact express itself at least "mostly" as single card moves. That's not
necessarily definitive. I think I've observed that perhaps some of its
moves move two cards, but maybe no more. Shlomi's Freecell Solver, however,
does use more multiple-card moves. I believe Shlomi does use moves that go
beyond the capability of M/S Freecell's rules. In as far as I got in
integrating his solver into FcPro, I actually did add, using a very light
touch, a conditional modification to FcPro's playback code to accept these
moves. Where I got hung up was in the inconsistency of moves to empty
stacks, and also, in at least one case, in the fact that an FCS solution
left an ace in a freecell. I would advocate a "standard" format that did
not employ a third character, but that there might be, as Bill suggested, a
code to indicate a choice for at least two mutually independent parameters
(1) Whether moves to empty columns are (a) single card or (b) multiple card
(in which case they are always the maximum number allowed according to a
specific formula). and (2) Whether automatic moves to the foundation are
included or excluded. But I have a feeling that this could get more
complicated than would be worth the trouble.
The evaluation of a solution, then, as Bill expresses it, is essentially
to design a yardstick to measure the merit of any given solution, i. e., its
brevity or lack of same. The design of the yardstick could well make or
break the awarding of a "prize" for the shortest solution. So the
environment (or "audience") for which the solution is intended becomes
important.
I'm not sure I really grasp Tom's meaning when he says that multiple
card moves can be "inefficient". It would seem this would depend on just
what definition of "efficiency" is intended. Do you mean, Tom, that the
solver become handicapped in its ability to arrive at a "verdict" as between
solvability or non-solvability of a given position in the shortest possible
time if it uses multiple-card moves instead of restricting itself to
single-card moves?
I should repeat here some of what I wrote to Shlomi in a side message:
---------------------------------------------
I'd say there are three distinct possible goals for a Freecell Solver
design:
(1) To find as many solutions as possible, regardless of size, to as many
boards as possible in the least time.
(2) To find as many solutions as short as possible, to as many boards as
possible in the least time.
(3) To deliver a completely trustworthy verdict as to the solvabililty of as
many boards as possible in the least time.
Of those three, (1) and (3) can be evaluated in a definitive way. Two
solvers can be compared on an absolute basis as to their effectiveness over
a given range of boards. (2), however, would be ambiguous as to its
evaluation, since one could always trade speed for shortness of solution.
Now, then, I would add that the "ideal" solver would be capable of
operating in any of the above three modes.
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Re those three categories, my own highest priority, so serve the needs
of the FcPro users community, would focus on (3). Shlomi freely admits he
is concentrating on (1) and (2). Tom takes the (3) requirement very
seriously, but is also pursuing (2), and provides a parameter to chose the
emphasis between the two goals.
Best regards, ------------------Adrian
Received on Mon Dec 10 2001 - 04:34:04 IST