Re: Mathematica goes Bad
- To: mathgroup at smc.vnet.net
- Subject: [mg59479] Re: [mg59422] Mathematica goes Bad
- From: Curtis Osterhoudt <gardyloo at mail.wsu.edu>
- Date: Wed, 10 Aug 2005 02:58:06 -0400 (EDT)
- References: <200508090730.DAA19089@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
I did not test your timing examples, not having anything other than
Version 5.1 handy. However, your limit-taking example wasn't typed in
well or something, I'm sure. What I suspect is the corrected version
follows:
{Limit[ArcTan[k], k -> +\[Infinity], Direction -> -1],
Limit[ArcTan[k], k -> -\[Infinity], Direction -> 1]}
Out[25]=
Pi Pi
{--, -(--)}
2 2
Version 5.1 gives you the correct answer, when the input is what (I
suspect) you meant. And I'll bet that 5.2 does, too.
Regards,
Curtis O.
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.
>
>
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- References:
- Mathematica goes Bad
- From: "Igor Touzov" <igor@nc.rr.com>
- Mathematica goes Bad