What's New - June 2002



June 27, 2002:  More brain candy for the younger set.   The SafeCracker program represents an unusual  safe.  Each of the buttons must be pressed in the correct order to open it.    The distance to move and the direction are indicated on each button.  The last button is marked  "LAST".  The safecracker's job is to locate the first button and unlock the safe by clicking  the chain of buttons from first to last.   (By the way, even though the image at left looks computer playable, it's not, so save your clicking finger.  You can copy it to paper and try it though.   You can also follow the link above to download the executable or Delphi source code for SafeCracker in order to generate and solve many puzzles of many sizes.)


June 20, 2002:  One of the proposed changes for the Traveling Salesman Program was implemented today.  It was just too good to resist,  reducing exhaustive search times for the 13 city closed route by 94% and increasing the maximum practical search size by a city or two.    See the Further Explorations section at the bottom of the Traveling Salesman Program page for more details. 

June 18, 2002:  The Traveling Salesman Problem is interesting because it is easy to state but hard to solve.   Given a set of cities, plan a roundtrip for our salesman that visits all the cities and minimizes the total distance traveled.    This turns out to be a very hard problem because of the explosion of possible paths as the number of cities increases.  Examining all paths is probably only practical up to 13 or 14 cities.  Above that number we need heuristic algorithms that give  pretty good results.   Lots of academics are spending lots of time finding better solving techniques with some success, but you won't find that code here.  You can try your  hand at beating the heuristics in my Traveling Salesman Program.   Or benchmark your computer by timing an exhaustive search for a 13 city path.     

June 13, 2002:  One of the early experiments in machine learning was a  "machine" which  used matchboxes and colored beads to play tic-tac-toe.  It was invented by Dr. Donald Michie over 40 years ago.  300 (or perhaps 304) matchboxes represent the the board positions presented to the machine.  For each move, a bead is selected randomly from the appropriate matchbox.  At the end of the game, wins are rewarded by more of the winning beads and losses punished by confiscating beads. You can train this computerized version of the  TicTacToe machine for yourself.   

June 3, 2002:  Here's an  Equation Search program that can be quite challenging to play.   Given four sets of four numbers each, find an arrangement of the numbers combined with two operators to form an equation of the form (N1 op1 N2) op2 N3 = N4 that is satisfied by each of the sets of numbers.  Operator choices may be restricted to from1-4 operator types chosen from +, -, , and  .     Problems are randomly generated by the program. Use all four operations and allow number values up to 99 and it can take a while to "unlock the code".