Re: Mathematica goes Bad
- To: mathgroup at smc.vnet.net
- Subject: [mg59460] Re: [mg59422] Mathematica goes Bad
- From: Murray Eisenberg <murray at math.umass.edu>
- Date: Wed, 10 Aug 2005 02:56:47 -0400 (EDT)
- Organization: Mathematics & Statistics, Univ. of Mass./Amherst
- References: <200508090730.DAA19089@smc.vnet.net>
- Reply-to: murray at math.umass.edu
- Sender: owner-wri-mathgroup at wolfram.com
Every one of your three examples has syntax errors.
Igor Touzov wrote:
> I am using Mathematica second year already, and found that each consequative
> version cuts off something good from what mathematica used to be.
>
> Contacting technical support only results in open ticket that never gets
> closed.
>
> Here some simple example you can run for youself:
> Timing[
> Limit[ (a ^2 k ^2 ArcTan[ ( (-a ^2 ) Cot[ [Theta]] - w y
> Tan[ [Theta]] ) / (a @ (a ^2 + ((w - y) ) ^2 + y ^2
> Tan[ [Theta]] ^2 ) )]
> Sin[2 [Theta]] ) / (2 + 2 k ^2 Sin[ [Theta]] ^2 ), [Theta] -> 0]] )
>
> It takes less then 1 ms on version 5.0, while for version 5.2 it will take
> forever (40.328 Second).
>
> Timing[
> Limit[ArcTan[ (a ((a k - w + y) ) Cot[ [Theta]] + k y ^2 Tan[
> [Theta]] ) / (y @ (a ^2 + ((w - y) ) ^2 + y ^2 Tan[ [Theta]] ^2 ) )],
> k -> (+ [Infinity] ), Direction -> 1]] )
>
> It takes 76.782 Second is version 5.0, 100.187 Second in version 5.1.1 and
> 104.015 Second in version 5.2.
>
> Not to mention it gives you some absurd results as well:
>
> In version 5.0 computing following
>
> {Limit[ArcTan[k ], k -> + [Infinity], Direction -> -1],
> Limit[ArcTan[k ], k -> + [Infinity], Direction -> 1]} results in accurate
>
> {-(Pi/2), Pi/2}
>
> while doing the same in version 5.2 gives you absurd {(Pi/2), Pi/2}.
>
> I could continue with list of examples that shows much more. But it only
> proofs the fact that whoever makes these changes in old good mathematica
> should be discharged. If some day I will get response from technical support
> that contains something meaningful I will post an update. Till then I would
> advise every body not to trust in results you get.
>
>
>
>
>
>
--
Murray Eisenberg murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2859 (W)
710 North Pleasant Street fax 413 545-1801
Amherst, MA 01003-9305
- References:
- Mathematica goes Bad
- From: "Igor Touzov" <igor@nc.rr.com>
- Mathematica goes Bad