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]