What we may have here is a difference between depth first and breadth first. In my depth first solver, finding out about the alternate path that moves the 3C is more easily done by simply backing up and doing it. If a layout gets repeated, moves from that point are all pruned. I’m not sure how I would program detecting the futility of the alternate moving of the 3C. Sorry, but I don’t think I’ve helped. -Gary
From: dannyjones183
Sent: Monday, October 08, 2012 4:50 PM
To: fc-solve-discuss_at_yahoogroups.com
Subject: Re: Missed Pruning Opportunity ?
--- In mailto:fc-solve-discuss%40yahoogroups.com, "Gary Campbell" <gary_at_...> wrote:
>
I'm not sure what was different between your two posts, but I'll respond to this one.
*** I originally wrote 2C instead of 2H at one place in my message, so I had to delete and repost the message FOR ONE STINKIN' CHARACTER.
My definition of a pruning opportunity is (1) all moves can be ignored if a layout has been reached before, or (2) all moves but one can be ignored from a layout if it can be proven that the one move cannot possibly prevent a solution, or (3) a particular move can be ignored if it can be proven (with little or no look ahead) that it cannot possibly lead to a solution. Have I missed anything?
*** I'll need to review your comments further.
In your scenario, we have 2 choices at move 10: (10. 61) and (10. 15). While I would always try (10. 15) first, both moves are irreversible, and I don't see how you could prove that (10. 61) could not possibly be necessary to a solution (without some kind of look ahead). Neither subsequent sequence of moves leads to a repeated layout (until you come to the last move, at which point there are no more moves possible).
Somehow, I get the feeling you don't see it as being this simple, so I must be missing something.
*** I've reviewed the five moves -- 15 65 a6 5a 5h : 3C 2H 9S 2H 3C -- many times while looking for an idea on how to prune it. It occurs to me that there is a pruning option.
*** After making the final move for 3C, I find the previous move for 3C and see if not performing it would still allow the intermediate moves -- 2H-3C 9S-TH 2H-FC 3C-HC -- to occur. If the first 3C move doesn't prevent the subsequent moves, then it can be pruned. Looking back at the two move sequences that I originally posted, this deduction now seems obvious. (see below)
*** I suspect that this falls under one of Gary's (1-3) above.
>
> From: dannyjones183
> Sent: Monday, October 08, 2012 12:26 PM
> To: mailto:fc-solve-discuss%40yahoogroups.com
> Subject: Missed Pruning Opportunity ?
>
> #88445005 Attempt: 1 NumFcs=4 (Hrn Super)
>
> 7a 7b 7c 7d b7 5b d7 17 6d 15 65 a6 5a 5h
> 9S 9H 5S 8C 9H 7H 8C 7D 5D 3C 2H 9S 2H 3C
> | | | | | | | | |
> 7a 7b 7c 7d b7 5b d7 17 6d 61 a6 1a 1h
> 9S 9H 5S 8C 9H 7H 8C 7D 5D 2H 9S 2H 3C
>
Received on Mon Oct 08 2012 - 17:05:48 IST