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MathGroup Archive 2007

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Re: Re: Re: Weird result in Mathematica 6

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76626] Re: [mg76574] Re: [mg76431] Re: [mg76393] Weird result in Mathematica 6
  • From: János <janos.lobb at yale.edu>
  • Date: Fri, 25 May 2007 06:21:32 -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>

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.

J=E1nos
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,
>>>>>>>      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
>>
>>
>
>
>
> --
> DrMajorBob at bigfoot.com



----------------------------------------------
Trying to argue with a politician is like lifting up the head of a 
corpse.
(S. Lem: His Master Voice)



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