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Re: How to get the Inverse matrix in symbolic way?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114478] Re: How to get the Inverse matrix in symbolic way?
  • From: Daniel Lichtblau <danl at wolfram.com>
  • Date: Sun, 5 Dec 2010 21:53:11 -0500 (EST)


----- Original Message -----
> From: "lightnation" <lightnation at naver.com>
> To: mathgroup at smc.vnet.net
> Sent: Saturday, December 4, 2010 5:11:59 AM
> Subject: [mg114422] How to get the Inverse matrix in symbolic way?
> The attached file is for getting the inverse matrix in the symbolic
> way, in the power system.
> 
> http://blog.daum.net/lightnation?t__nil_loginbox=blog_btn&nil_id=1
> 
> 
> You can see the message "Mathematica Kernel has been shut down." after
> running this file,
> or only to find the file running infinitely.
> 
> If Mathematica cannot get the inverse matrix, I'd be very
> disappointed,
> 
> because this matrix is very important for the power system analysis.

I doubt you can get a reasonable result (if you can get any symbolic result, in finite time). The matrix you have is 12x12, not especially sparse, and contains several variables, trig functions thereof, etc. The only way a usable result might emerge is if it has some banded structure (or can be permuted to have one) that I didn't see, and also gives ries to fortuitous cancellations in the process of row reduction. Else I would expect the result to be monstrously big even in simplified form.

It might in principle be possible to get a smaller form by judicious use of common subexpression elimination. But I do not know how to go about this in any way that would actually be likely to succeed.

I could be wrong, but I really expect you will need to work with these after numeric values are put in for the various parameters, rather than before.

Daniel Lichtblau
Wolfram Research



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