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MathGroup Archive 2005

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Re: Re: Re: Bug in 5.1??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54571] Re: [mg54528] Re: [mg54469] Re: Bug in 5.1??
  • From: DrBob <drbob at bigfoot.com>
  • Date: Wed, 23 Feb 2005 03:11:42 -0500 (EST)
  • References: <200502210844.DAA27157@smc.vnet.net> <200502220923.EAA10793@smc.vnet.net> <03d46b8e970e9ccc74c8324d28644629@mimuw.edu.pl>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

I don't file bug reports because (a) I don't usually have real applications that warrant it (certainly not in this case) and (b) reporting bugs is a pretty fruitless endeavor -- even if WRI _is_ a hundred times more responsive than Microsoft (for instance) in that regard. Nothing gets fixed until the next release, and many bugs have already survived five years or more. I am likely to get a work-around from tech support, but I can come up with work-arounds on my own.

Anyway, WRI can't claim to be unaware of this problem, or anything else we discuss in this forum -- regardless of whether anybody files a bug report.

I do understand that developmental priorities and theoretical issues make it impractical to fix some of these things. Generally, I'm not really asking anyone to fix them; I just want to understand, to whatever extent I can. Possibly you think I'm far more concerned than I actually am.

As for 2-digit significance arithmetic in particular, if I want an explanation and you don't have one, and you clearly don't care about the issue, why answer?

Bobby

On Tue, 22 Feb 2005 15:37:35 +0100, Andrzej Kozlowski <akozlowski at gmail.com> wrote:

> Your response is very curious. Who told you you are not supposed to
> complain? I suggested you file a bug report. If you do not file one
> presumably you have a reason?? Is the reason that (you imagine) I told
> you not to complain? I am flattered to see that I now wield this sort
> of authority but really I do not seek it. I only told you that in the
> past people wrote write about such issues and, in the old days, someone
> (usually David Withoff) would respond. But even he never gave, as far
> as I can recall,  a clear reason why this happens, only a vague one
> like the one I have given: strange things happen if you use
> significance arithmetic at low precision,and try making comparisons
> like
>
> 10`2 ==0
>
> True
>
> or
>
> 100`2==0
>
> True
>
> or whatever. Don't do it.
>
> So now please do file a bug report and demand an explanation. I will be
> very interested to read the response, if you get one of course. After
> all, I am just another user and have no better access to WRI's thinking
> than you have.
>
> Andrzej Kozlowski
>
>
>
>
> On 22 Feb 2005, at 10:23, DrBob wrote:
>
>> It doesn't make sense to ANYBODY, as far as I can tell.
>>
>> But we're not supposed to complain, because somebody ALREADY
>> complained (some time or another).
>>
>> Bobby
>>
>> On Mon, 21 Feb 2005 03:44:38 -0500 (EST), Dana DeLouis
>> <delouis at bellsouth.net> wrote:
>>
>>> Seems to me that the loss of precision returns an "Interval", which
>>> is still
>>> greater than zero.  It looks like the cutoff between True & False is
>>> a hair
>>> above -1, which doesn't make sense to me either.
>>>
>>> Interval[N[5, 2]]
>>> Interval[{4.9, 5.1}]
>>>
>>> N[5, 2] > -1
>>> True
>>>
>>> N[5, 2] > -1 + $MachineEpsilon
>>> False
>>>
>>
>>
>>
>> --
>> DrBob at bigfoot.com
>> www.eclecticdreams.net
>>
>>
>
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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