What's New -  June 2003

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June 27, 2003:   A replacement version of the Spring Mass 1 program was posted today.  It's an animated demo program of a simple spring-mass system with user controlled parameters.  Fellow Delphian Don Rowlett had spotted a  bug or two and suggested some changes.  I  fixed the bug and added a couple of other features as a bonus.   The exercise reminded me that I had planned a Spring Mass 2 program to handle multiple coupled springs and masses.   It's back on the active list (which still may stretch into next winter). 

June 13, 2003:  Alert viewer Charles Doumar  sent code to correct the "corner" problem with yesterday's Knight's Tour posting (specifying any corner for an end point results in long search times).   I posted the revision  today.   It looks like the problem with "next  to corner" end points remains though (any end point one knight move removed from a corner).   Charles will be working on it this next week - and I'll be at the beach on vacation!  (Well,  I will have my laptop with me in case of rain <g>.)   See you in a week. 

June 12, 2003: A simple modification to the Knight's Tour program was posted today which allows users to specify an ending square as well as a beginning square for program solution searches.    In most cases a procedure similar to that used for "closed tour" searches will find a solution in a few hundred trial moves.   However, a test case starting at square (1,1) and ending at square (8,1) was  stopped after 10,000,000 trial moves, so there is obviously room for a smarter method! 

June 11, 2003: An alert user recently spotted a bug in our Multi-Pile Nim program.  In the  "last token loses"  version, the computer could lose if the human played well - but proudly announced: "Computer wins again!" after losing!.   The replacement  version posted today may still lose but now he at least admits it.

 

June 10, 2003:  Here is #7 in the numeric t-shirt series.   These hypothetical t-shirts are primarily programming exercises.   The back of this shirt reads:  "The only set of  prime numbers containing all of the digits 1 through 9 and whose sum is a 3-digit number."   And the front of the shirt reads:

See the answer and check out the code at T-Shirt #7

 

June 8, 2003:  Summertime things are not leaving much spare time for programming this month, but I do have a request.  The other day, a viewer asked  if I could design a a Knight's Tour that  starts and ends on specific squares.     I'm not aware of a specific algorithm for this,. but maybe one of our knowledgeable viewers does.  If you can shed any light on this variation of the problem,  please  drop me a line.    In the the meantime, I'm going to refresh my memory and take a look at our existing Knight's tour program to see if it can be easily modified to target a specific square as the final move.