Re: [femm] FEMM Vs. commercial code

[Keith Gregory <k.gregory@xxxxxxxxxxx>]

Well ....

There are many differences between FEMM and typical commercial code but I 
don't think that in the important area (i.e. kern - the solver ) there is 
much difference. FEMM is as good as if not better than a lot of commercial 
stuff. David has taken advantage of a very good mesh generator and produced 
an excellent piece of software. That said it is not bullet proof and David 
would be the first to admit that it does fall over occasionally in ways 
that most commercial code would not. This to me is part of its attraction, 
I use FEMM for teaching and it makes students think much more about what 
they are doing than most commercial code would. It also has the significant 
advantage for those who have little nor no spare money (i.e UK Academics!) 
that it is free in a market that is occupied by software that can be 
inordinately expensive. The first commercial finite-element code that I 
ever used required a main-frame to run it and cost over £10,000 (around 
$30,000 in those days).

The problem that I have with a lot of commercial code is that it is 
overblown, by which I mean that it covers up a lot of what it is doing in 
the name of an easy user interface. FEMM does not do that although its user 
interface is one of the most straightforward that I have ever come across - 
only one commercial code that I know of comes close for ease of use. FEMM 
does not have any of the almost CAD like drawing tools that commercial code 
usually has. However, a little bit of ingenuity and old fashioned 
draftsmanship usually allow a problem to be drawn directly in FEMM. I only 
resorted to DXF import in the earlier versions of FEMM I feel no need to now.

FEMM does not have adaptive meshing you have to refine meshes by hand where 
most commercial code does it automatically. I do not find this to be a 
problem because most computers these days eat large problems so often I 
just use fine meshes!

FEMM does not include other integrated solvers such as the electrostatic, 
thermal or mechanical stuff that some commercial software includes.

FEMM requires you to set boundary conditions explicitly where (I think) 
some commercial codes can do it (semi?) automatically.

FEMM circuit facilities are in their infancy for example they cannot 
directly integrate external circuitry as many commercial codes can. (I am 
of the opinion though that this may be possible using lua scripts).

FEMM cannot deal with dynamic (transient) situations as some commercial 
codes can.

FEMMVIEW (the postprocessor) has most if not all of the tools that 
commercial code has but requires you to understand what they do in order to 
use them effectively. Many commercial codes attempt to determine things 
like inductance at the push of a button, this has always worried me and I 
find I don't trust the results. That said FEMMVIEW does not produce such 
polished results as most commercial code and lacks some of the common 
plotting facilities such as vector displays.

FEMMPLOT is useful but not something that you would use to produce 
presentations. Most commercial code can produce camera ready stuff (all 
show no substance?).

The addition of lua scripting has given FEMM very powerful facilities that 
far exceed many commercial efforts. One of my undergraduate project 
students is now using FEMM in conjunction with MatLab and lua scripts of 
hundreds of lines of code to produce very effective interactive design tools.

I have found, over a few years of use now, that FEMM can do virtually 
everything that I need to do as well as and sometimes better than the 
commercial code that I have used in the past.

FEMM is a simple, straightforward but very powerful piece of software that 
does exactly what it says on the tin! (apologies for a reference that may 
only be understood in the UK). Finally, FEMM has one singular advantage 
over all commercial software - it's written and maintained by someone who 
is not anonymous, who will talk to you and listen to what you say. You 
cannot put a price on that.

Keith.





At 21:43 12/11/2002 +0100, you wrote:
> Which are main differences?
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