Re: Re: Weird result in Mathematica 6
- To: mathgroup at smc.vnet.net
- Subject: [mg76559] Re: [mg76431] Re: [mg76393] Weird result in Mathematica 6
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Thu, 24 May 2007 05:55:26 -0400 (EDT)
- References: <26727995.1179743868970.JavaMail.root@m35> <200705220647.CAA19795@smc.vnet.net> <9745176.1179921476358.JavaMail.root@m35> <op.tssgfzliqu6oor@monster.ma.dl.cox.net> <4431163.1179955154502.JavaMail.root@m35> <op.tsstz4blqu6oor@monster.ma.dl.cox.net>
That means definitely "platform dependence". It would be interesting if somone checked this on an Intel Mac. I think it is much more likely to be the processor than the operating system that makes the difference here. I don't know much about such things, but some processor specific libraries could be responsible for this. Andrzej On 24 May 2007, at 06:29, DrMajorBob wrote: > $Version > > "6.0 for Microsoft Windows (32-bit) (April 20, 2007)" > > Bobby > > On Wed, 23 May 2007 16:17:31 -0500, Andrzej Kozlowski > <akoz at mimuw.edu.pl> wrote: > >> Yes, its curious. It might just be "platform dependence" but is >> more likely to be "time of release dependence". Mine is: >> >> >> $Version >> >> "6.0 for Mac OS X PowerPC (32-bit) (April 20, 2007)" >> >> Andrzej >> >> >> On 24 May 2007, at 01:37, DrMajorBob wrote: >> >>> Interesting. But your results are entirely different from mine, >>> for the same input. >>> >>>> which explains what is wrong (error messages can tell you a lot, = >>>> sometimes). >>> >>> And frequently, they don't. >>> >>> Here's the error message at THIS machine: >>> >>> FindRoot::lstol: The line search decreased the step size to within \ >>> tolerance specified by AccuracyGoal and PrecisionGoal but was >>> unable \ >>> to find a sufficient decrease in the merit function. You may need \ >>> more than MachinePrecision digits of working precision to meet >>> these \ >>> tolerances. >> >>> >>> Bobby >>> >>> On Tue, 22 May 2007 06:28:08 -0500, Andrzej Kozlowski >>> <akoz at mimuw.edu.pl> wrote: >>> >>>> *This message was transferred with a trial version of CommuniGate= >>>> (tm) Pro* >>>> I don't see any connection between these two issues. Moreover, I = >>>> get: >>>> >>>> FindRoot[h == g, {x, 0}] >>>> FindRoot::njnum:The Jacobian is not a matrix of numbers at {x} = = >>>> {0.}. >> >>>> {x -> 0.} >>>> >>>> which explains what is wrong (error messages can tell you a lot, = >>>> sometimes). Trying a slightly different starting search point: >>>> >>>> FindRoot[h == g, {x, 0.1}] >>>> {x->2.} >>>> >>>> {g, h} /. % >>>> {0., 0.} >>>> >>>> >>>> Andrzej Kozlowski >>>> >>>> >>>> On 22 May 2007, at 15:47, DrMajorBob wrote: >>>> >>>>> Even worse, FindRoot returns a wrong answer: >>>>> >>>>> g = Piecewise[{{0, x < 0}, {2 x - x^2, 0 <= x < 4}, {16 x - = x^2, >>>>> x=B34}}]; >>>>> h = x - 2; >>>>> FindRoot[h == g, {x, 0}] >>>>> {g, h} /. % >>>>> >>>>> {x->-2.84217*10^-15} >>>>> {0, -2.} >>>>> >>>>> Bobby >>>>> >>>>> On Mon, 21 May 2007 05:01:21 -0500, Sebastian Meznaric >>>>> <meznaric at gmail.com> wrote: >>>>> >>>>>> I was playing around with Mathematica 6 a bit and ran this >>>>>> command to >>>>>> solve for the inverse of the Moebius transformation >>>>>> >>>>>> FullSimplify[ >>>>>> Reduce[(z - a)/(1 - a\[Conjugate] z) == w && a a\[Conjugate] = >>>>>> < 1 && >>>>>> w w\[Conjugate] < 1, z]] >>>>>> >>>>>> This is what I got as a result: >>>>>> -1 < w < 1 && -1 < a < 1 && z == (a + w)/(1 + w Conjugate[a]) >>>>>> >>>>>> Why is Mathematica assuming a and w are real? The Moebius >>>>>> transformation is invertible in the unit disc regardless of >>>>>> whether a >>>>>> and w are real or not. Any thoughts? >>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>> --DrMajorBob at bigfoot.com >>>>> >>>> >>>> >>> >>> >>> >>> --DrMajorBob at bigfoot.com >> >> > > > > -- > DrMajorBob at bigfoot.com
- References:
- Re: Weird result in Mathematica 6
- From: DrMajorBob <drmajorbob@bigfoot.com>
- Re: Weird result in Mathematica 6