zgeev for AX=0

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zgeev for AX=0

Postby Zahra » Sat Feb 18, 2012 3:43 am

Dear all,

I used the routine zgsevd for finding the X of AX=0. But while S(16) is small (in order of 10^-8), AX is of order of 10^-1. Here, I've taken the 16 column of VT to be X. Indeed this X can't be the solution of AX=0. Am I doing something wrong? would you please help?

Also, is there any other method that I can use to find the nontrivial solutions of AX=0?

Also, if I use zgeev. when eigenvalue is zero, does the eigenvector show the nontrivial solution of AX=0? I don't know if zgeev is capable of showing nontrivial solution.

Bests
Zahra
 
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Re: zgeev for AX=0

Postby Julien Langou » Sat Feb 18, 2012 12:50 pm

The 16th row of VT is the solution of AX=0.
(Not the 16th column.)
Julien Langou
 
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Re: zgeev for AX=0

Postby Julien Langou » Sun Feb 19, 2012 1:16 am

Also, if I use zgeev. when eigenvalue is zero, does the eigenvector show the nontrivial solution of AX=0? I don't know if zgeev is capable of showing nontrivial solution.

Yes it should work, it is less stable than zgesvd though.
Julien
Julien Langou
 
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