[SI-LIST] Re: spectral domain vs BEM (was non-negative......)
- From: Chris Cheng <chris.cheng@xxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 4 Sep 2001 15:00:04 -0700
the point i was trying to say was :
i was always told that in FEM, you can't explicitly pivot the
n diagonal sparse matrix and have to use ICCG while in
BEM you can use LU since the matrix is small but dense. i
thought the underlying assumption is explicit is exact while
implicit is converge so explicit is a better choice. given we
see round off error in LU, maybe we should rethink the argument.
i particular the round off gets propagated forward with LU while
in ICCG the round off is reset in every interation.
chris
-----Original Message-----
From: Ray Anderson [mailto:Raymond.Anderson@xxxxxxx]
Sent: Tuesday, September 04, 2001 2:50 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: spectral domain vs BEM (was non-negative......)
Mick-
I was responding to Chris's query about which algorithm the
tool used. He was wondering about which inversion method might
have been used.
I agree, whether the off-diag elements are non-positive or not
depends on the definition of the matrix, but we jumped topics
to discuss another aspect.
-Ray
>
>
>
>>
>>Looks like you are discussing the mathematical aspects of different
>>algorithms. But I think the
>>original question is about the physical aspects. Should the off-diagonal
>>elements be non-positive
>>or non-negotive ? Fortunately, we can answer it directly based on the
>>definitions, independent of any numerical examples. It does not matter
how
>>you calculate them. So, we can judge the mathematical results. It is very
>>true that all algorithms have drawbacks which lead to numerical
>>difficulties and errors.
>>
>>Mick
>>
>>
>>-----Original Message-----
>>From: Ray Anderson [mailto:raymonda@xxxxxxxxxxxxxxxxxxxxxxx]
>>Sent: Tuesday, September 04, 2001 4:39 PM
>>To: si-list@xxxxxxxxxxxxx
>>Subject: [SI-LIST] spectral domain vs BEM (was non-negative......)
>>
>>
>>
>>One of the Apsim guys may want to comment, but I believe that the
>>Apsim RLGC tool that I was using implements the spectral domain
>>method which I think is similar to BEM in some respects but
>>different in others. (I'm going to stop right here, I only
>>know enough about this to be dangerous :)
>>
>>RLGC can optionally use the FEM, but it is recommended that FEM be
>>utilized for more complex structures that are defined with multiple
>>dielectrics than simple stripline constructs.
>>
>>
>>-Ray
>>
>>
>>
>>>
>>>
>>>which brings into another question,
>>>ray,
>>>was the tool using FEM (most likely using ICCG) or
>>>BEM (most likely using LU)?
>>>chris
>>>
>>
>
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