Re: Reduce in Mathematica 5 vs Mathematica 8 (2nd problem)

*To*: mathgroup at smc.vnet.net*Subject*: [mg115260] Re: Reduce in Mathematica 5 vs Mathematica 8 (2nd problem)*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 5 Jan 2011 05:48:33 -0500 (EST)

On 5 Jan 2011, at 00:53, olfa wrote: > Hi Mathematica Community, > > First,wish you happy and successfull new year. > > For this 2nd problem in the same subject,I have this system to solve: > > Reduce[Not[ > ForAll[{aaP, abP, iP, jP, sP, tP, uP, xP, yP, zP}, > Implies[t == tP && i + x == iP + xP && y == yP && > j t + z == jP tP + zP && t x + z == tP xP + zP && > Floor[Log[j]/Log[2]] == Floor[Log[jP]/Log[2]] && > Floor[Log[x]/Log[2]] == Floor[Log[xP]/Log[2]] && x >== xP, > t x == tP xP]]]] > > in mathematica 5 the output is given in a very short time and is "the > system cannot be solved with the method available to Reduce" this > suits me (although I wish it to be the output "True" which is the > right answer) > > in mathematica 8 the kernel still in running indefinitely and this > does not suit me at all :( > > so how to deal with that? > > e.g TimeConstrained[ Reduce[Not[ ForAll[{aaP, abP, iP, jP, sP, tP, uP, xP, yP, zP}, Implies[t == tP && i + x == iP + xP && y == yP && j t + z == jP tP + zP && t x + z == tP xP + zP && Floor[Log[j]/Log[2]] == Floor[Log[jP]/Log[2]] && Floor[Log[x]/Log[2]] == Floor[Log[xP]/Log[2]] && x >== xP, t x == tP xP]]]], 5] $Aborted Andrzej Kozlowski P.S. You should have noticed by now that Reduce can never deal with anything involving Floor. See, for example: In[5]:== Reduce[Floor[x] <== x && x > 0, x, Reals] During evaluation of In[5]:== Reduce::nsmet:This system cannot be solved with the methods available to Reduce. >> Out[5]== Reduce[Floor[x] <== x && x > 0, x, Reals]