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MathGroup Archive 2001

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out of memory, again.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg27473] out of memory, again.
  • From: "Ivan Stegic" <ivan at stegic.com>
  • Date: Tue, 27 Feb 2001 00:37:25 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

hi again...

you may remember the problem i outlined below. i received some help, and
managed to find the eigenvectors. luckily, i am not interested in all
three, rather only the real eigenvector. it turns out that the real eigen
vector is a text file of about 60kb containing cos and sin of two
parameters... ive tried to simplify each component in turn using
FullSimplify, to which the machine crunches for about 26 hours, and spits
out another out of memory exiting message. are there any wise ideas, or
clever tricks i may try? perhaps someone out there has a machine which
could attack the simplification by brute force? i would ofcourse cite your
help, if you like. the eigenvector was too hefty to attach, so i uploaded
it to the web.

1st comp: http://stegic.com/1stcomponent.dat
2nd comp: http://stegic.com/2ndcomponent.dat
3rd comp: http://stegic.com/3rdcomponent.dat (unity!)

and the single eigen vector as a whole, for completeness:
http://stegic.com/N.dat

any advice, help, comments appreciated.

ivan, the desperate.


--- Original Message ---

>Hello everyone...
>
>I've searched the archives extensively, and found various answers to my
>problem. However, none of them helped me. I am trying to find the
>eigenvectors to a 3x3 matrix. I keep running into Out of Memory Exiting
>problems, whether I run it with the frontend or without. I am running
>Mathematica 3 on a RedHat Linux 5.1, Kernel 2.0.35  Pentium II 400 with
>128MB of RAM. The matrix I have contains 2 variables, and I am trying to
>solve the for the Eigenvectors symbolically in terms of these variables.
>The catch is that the variables are trigonometric functions. Following is
>the command I execute. The result is "Out of Memory. Exiting." What can I
>do? Could someone else try this on their more powerful machines, or will
it
>still run into the same problem? Or is there a way of simplifying this? Or
>the matrix?
>
>Thanks very much,
>Ivan.
>
>
>------------------------
>[ivan@apollo ivan]$ more jobs/i.txt
>Eigenvectors[{{Cos[q]^2 - Cos[2*p]*Sin[q]^2,
>    1.*(Sin[2*p]*Sin[2.*p]*Sin[q] + Cos[p]^2*Cos[2.*p]*Sin[2*q]),
>    1.*Cos[2.*p]*Sin[2*p]*Sin[q] - 1.*Cos[p]^2*Sin[2.*p]*Sin[2*q]},
>   {-(Cos[p]^2*Sin[2*q]), 1.*Cos[q]*Sin[2*p]*Sin[2.*p] -
>     1.*Cos[2.*p]*(-(Cos[2*p]*Cos[q]^2) + Sin[q]^2),
>    1.*(Cos[2.*p]*Cos[q]*Sin[2*p] +
>       Sin[2.*p]*(-(Cos[2*p]*Cos[q]^2) + Sin[q]^2))},
>   {Sin[2*p]*Sin[q], -1.*Cos[2.*p]*Cos[q]*Sin[2*p] +
1.*Cos[2*p]*Sin[2.*p],
>    1.*(Cos[2*p]*Cos[2.*p] + Cos[q]*Sin[2*p]*Sin[2.*p])}}]>>>EVec-Symb;
>[ivan@apollo ivan]$
>------------------------
>
>
>(For those who are interested, this matrix is a rotation matrix that takes
>the orthonormal basis of a cone rotating around a replica cone from its
>initial to its final position. p and q are the cone semi-angle, and the
>parametrized position of the rotated cone respectively.)



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