Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2011

[Date Index] [Thread Index] [Author Index]

Search the Archive

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]




  • Prev by Date: Re: Session Privacy in Mathematica 8 w/ Wolfram|Alpha free-form input?
  • Next by Date: Re: Combining Slider and SetterBar in Manipulate
  • Previous by thread: Reduce in Mathematica 5 vs Mathematica 8 (2nd problem)
  • Next by thread: Re: Reduce in Mathematica 5 vs Mathematica 8 (2nd problem)