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Subject: 
Re: Just a few highlights and points...
Newsgroups: 
lugnet.org.us.laflrc, lugnet.robotics
Date: 
Wed, 28 Sep 2005 16:35:53 GMT
Viewed: 
382 times
  
On Wed, September 28, 2005 11:03 am, Brian Davis wrote:
In lugnet.org.us.laflrc, Steve Hassenplug wrote:
Assuming you can identify an intersection, all the robot
really needs to know is where to go when it gets to an
intersection... doesn't need to track intersections [along
dead-ends]... doesn't need to know the distance[s]...
doesn't need to identify ["pure"] turns...

   Agreed. What it does right now is look for turns or intersections, making
choices only there. If it's just a turn (a "pure" turn), it makes it and doesn't
bother updating the memory of the path. Ideally (in other words, the untested
portion) when it hits a dead-end, it back-tracks to the last node in the tree,
pruning off this "dead branch" and choosing again - if there are no valid paths
to explore off this last node, it returns to the parent node in the tree,
pruning the newly-dead node from the tree again. Essentially, it's a depth-first
search of a graph or tree representation of the maze that is built dynamicly as
the robot traverses branches.
   It also means, currently, there are three things each node needs to have
recorded. The "structure" (compass heading of valid paths to explore from the
node - four bits), the last direction the node was left from (2 bits; this way
we know which direction to "prune" from the node if we are sent back here by a
deadend), and the heading back to the parent of this node (again, 2 bits). That
works out nicely to 8 bits per node, meaning I can pack two nodes of info into a
single NQC variable.

I must have done something wrong.  I'm only keeping 2 bits per node, instead of 8.

Steve



Message has 1 Reply:
  Re: Just a few highlights and points...
 
(...) Yes, I'm sure that's it - you just *imagined* you maze-solver worked ;-). (...) Hmm. OK, that's got me confused. I *know* I'm storing more information than needed, but each node in the path only takes 2 bits? If those two bits encode the (...) (19 years ago, 28-Sep-05, to lugnet.org.us.laflrc, lugnet.robotics)

Message is in Reply To:
  Re: Just a few highlights and points...
 
(...) I didn't read it. But if I had... (...) Agreed. although if we start running mazes with loops (like Alegomazer did) I think mapping, physically, the maze will likely be needed - if for no other reason than to know when you've closed a loop. (...) (19 years ago, 28-Sep-05, to lugnet.org.us.laflrc, lugnet.robotics)

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