Re: Re: Re: Weird result in Mathematica 6

*To*: mathgroup at smc.vnet.net*Subject*: [mg76737] Re: [mg76574] Re: [mg76431] Re: [mg76393] Weird result in Mathematica 6*From*: DrMajorBob <drmajorbob at bigfoot.com>*Date*: Sat, 26 May 2007 04:45:17 -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> <23418457.1179976106322.JavaMail.root@m35> <200705241003.GAA21171@smc.vnet.net> <1937054.1180123979329.JavaMail.root@m35>*Reply-to*: drmajorbob at bigfoot.com

Oh well. I'll go Mac next time. Back to the "FindRoot::lstol" error itself, though, I've never seen that occur when changing precision would actually fix the problem. Bobby On Thu, 24 May 2007 09:48:33 -0500, János <janos.lobb at yale.edu> wrote: > There are function calls in some OS libraries that are not working > correctly on AMD architecture. A good friend of mine in Hungary worked > for a software firm and the firm had just AMD machines. The only Intel > machine was his laptop. When it came to close out a major upgrade of > the firm software, all AMD machines reported problems and only his Intel > laptop gave the desired result. All AMDs were changed overnight for > Intel machines. > > János > On May 24, 2007, at 6:03 AM, DrMajorBob wrote: > >> I'm using an AMD 3200+ processor, in case that matters. >> >> Bobby >> >> On Wed, 23 May 2007 16:37:54 -0500, Andrzej Kozlowski >> <akoz at mimuw.edu.pl> >> wrote: >> >>> *This message was transferred with a trial version of CommuniGate(tm) >>> Pro* >>> 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: >>>> >>>>> *This message was transferred with a trial version of CommuniGate(tm) >>>>> Pro* >>>>> 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, >>>>>>>> x³4}}]; >>>>>>>> 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 >>> >>> >> >> >> >> --DrMajorBob at bigfoot.com > > > > ---------------------------------------------- > Trying to argue with a politician is like lifting up the head of a > corpse. > (S. Lem: His Master Voice) > > -- DrMajorBob at bigfoot.com

**References**:**Re: Weird result in Mathematica 6***From:*DrMajorBob <drmajorbob@bigfoot.com>

**Re: Re: Weird result in Mathematica 6***From:*DrMajorBob <drmajorbob@bigfoot.com>