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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: [mg54573] Re: [mg54528] Re: [mg54469] Re: Bug in 5.1??
  • From: Andrzej Kozlowski <akozlowski at gmail.com>
  • Date: Wed, 23 Feb 2005 03:11:44 -0500 (EST)
  • References: <200502210844.DAA27157@smc.vnet.net> <200502220923.EAA10793@smc.vnet.net> <03d46b8e970e9ccc74c8324d28644629@mimuw.edu.pl> <opsmlt5wcgiz9bcq@monster.ma.dl.cox.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 22 Feb 2005, at 16:18, DrBob wrote:

> 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?
>
Because when you tell anther user that he has "discovered" a bug, you 
are implying that he should take the trouble to report it, which is 
something you do not wish to do yourself because you know well that it 
will be a waste of effort. I, on the other hand, am telling him that 
what he has observed has been well known for 10 years +  and nothing 
has been done about it, for a variety of possible reasons, the most 
likley   being that this "problem" is considered harmless; other 
possible reasons being that nobody knows how to fix it or whether 
fixing it would damage other things or even perhaps because 
significance  arithetic can't work without something like that.

Andrzej Kozlowski





>
> 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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