       Massive memory issues when using Det

• To: mathgroup at smc.vnet.net
• Subject: [mg127323] Massive memory issues when using Det
• From: Jonathan Frazer <J.Frazer at sussex.ac.uk>
• Date: Tue, 17 Jul 2012 01:29:45 -0400 (EDT)
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• References: <20120711061823.1AE5D684B@smc.vnet.net>

Hi

I'm having a lot of trouble calculating the determinant of even a 3x3
matrix. The expressions are large but all aspects of the program are
handling them fine except Det.

Is Det trying to simplify the expressions by any chance? Is there
anything I can try? Below is an example of how I construct the matrix
but this example is much simpler. The difference is S\theta\alpha and
C\theta\alpha are bigger expressions in the real thing. As far as I
can tell the code is logically fine. It works for smaller dimension
problems with no trouble at all.

Right now I have been trying to evaluate Det for about 3 hours and its
taking up almost 12 GB of memory.

Jonny

On 11 Jul 2012, at 18:39,  wrote:

> d = 2;
> èá = Table[Symbol["è" <> ToString[i]], {i, d - 1}];
> Sèá = Sin[èá];
> Cèá = Cos[èá];
> sè = r Prepend[Table[Product[Sèá[[á]], {á, i}], {i, d - 1}], 1]*Append[Cèá, 1];
> ë = Outer[D[#1, #2] &, sè, èá];
> g = Table[Sum[ë[[ã, á]] ë[[ã, â]], {ã, d}], {á, d - 1}, {â, d - 1}];
> vol = Sqrt[Det[g]]
>



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