| Floating Underflow/Overflow [message #27249] |
Mon, 15 October 2001 06:13  |
bente
Messages: 13
Registered: October 2001
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Junior Member |
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Hi,
i get Floating Overflow/Underflow error messages during my
calculations, but the result seems to be correct, can these warnings
be ignored then?
I�m calculating a Fermi Distribution (I want a sphere with smooth
edges and this seemed to be the easiest way) I think, that the results
get to low for larger radiuses so IDL makes this error message. Is it
possible to tell IDL to round to zero then or what do i have to do?
with regards
Kay
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| Re: Floating Underflow/Overflow [message #27346 is a reply to message #27249] |
Thu, 18 October 2001 07:39  |
John-David T. Smith
Messages: 384
Registered: January 2000
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Senior Member |
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Kay wrote:
>
> Hi, again.
>
> Wow didn�t expected to get so much response ;-)
>
>> On the other hand, the performance of IDL falls down rather badly when
>> dealing with conditional tests on large arrays, especially when FOR
>> loops cannot be avoided. Even using WHERE() usually makes a pretty
>> large performance hit.
>
> The peformance is the large problem I have, my PC isn�t so fast
> (350MHz with only 128MB Ram. And i have to work through a 256x256x128
> floating Point array with 3 FOR-Loops (i need the complete Indizes to
> get the Radius from a specific point to the current Voxel (don�t no
> some faster way to get this)
>
> It�s not so that this lasts hours then, but i gets annoying if you
> want to change a value a bit and then wait several minutes for the
> result
You can almost certainly speed this up by eliminating the FOR loops (OK,
Craig, eliminating the *inner* FOR loops). The traditional recipe for
going about this is as follows:
1. Post your problem clearly, with a small, distilled code example if
possible.
2a. Claim that you've put lots of thought into it, and there is no
vectorized solution possible.
and/or
2b. Claim that the vector solution is slower than the FOR loop
solution.
and/or
2c. Claim that the newsgroup just isn't what it used to be, so you
don't really expect a solution.
3. Sit back and watch the flies descend.
JD
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