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  1. Newsgroups: sci.math.symbolic
  2. Path: sparky!uunet!zaphod.mps.ohio-state.edu!wupost!spool.mu.edu!agate!boulder!fast
  3. From: fast@escher.colorado.edu (Bruce Alan Fast)
  4. Subject: mma big bad bug
  5. Message-ID: <1993Jan8.001216.26440@colorado.edu>
  6. Summary: the loop
  7. Sender: news@colorado.edu (The Daily Planet)
  8. Nntp-Posting-Host: escher.colorado.edu
  9. Organization: University of Colorado, Boulder
  10. Date: Fri, 8 Jan 1993 00:12:16 GMT
  11. Lines: 44
  12.  
  13. To get the first 25 steps of Mma calculations when it works on
  14. the (Pi/2)^(3/2)/3 bug,
  15.  
  16. In[3]:= loop = Trace[(Pi/2)^(3/2)/3][[Range[25]]];
  17.  
  18. $IterationLimit::itlim: Iteration limit of 4096 exceeded.
  19. ...etc.
  20.  
  21. Starting with the 4th element of 'loop' this three-fold cycle occurs
  22. for loop[[n]]:
  23.                  Pi 3/2
  24.                 (--)
  25.                  2        (n mod 3 = 1)
  26.                 -------
  27.                    3    
  28.  
  29.             /          \
  30.                /           \
  31.               /                \
  32.              /      the loop.        \
  33.             +                  \
  34. (n mod 3 = 0)
  35.                                   3
  36.             3                        Pi
  37.           Pi     Pi 3/2               Sqrt[---]       (n mod 3 = 2)
  38.     {Sqrt[---], (--)   }     <-------            8
  39.            8     2                   ---------
  40.                                3
  41.  
  42.  
  43. loop[[4]] = HoldForm[Times[
  44.     Power[Times[Pi, Power[2, -1]], Times[3, Power[2, -1]]],
  45.     Power[3, -1]
  46.     ]]
  47.  
  48. loop[[5]] = HoldForm[Times[
  49.     Power[Times[Power[Pi, 3], Power[8, -1]], Times[1, Power[2, -1]]],
  50.     Power[3, -1]
  51.     ]]
  52.  
  53. It's clear that there is a conflict between two ideas of 'Simplification'
  54. which bounces the expression between the two forms.  Someone (who knows more
  55. details of Mma simplification rules for Power & Times) please tell us what's
  56. happening.  Thanks.
  57.