[SciPy-user] do complex numbers default to double precision?

Ryan Krauss ryanfedora at comcast.net
Thu Jun 30 07:56:26 CDT 2005


The matrix is currently 4x4 but will grow to probably 6x6.  It is 
definitely nonlinear.  The matrix contains sinh, cosh, sin, and cos.  I 
am using the transfer matrix method to analyze structures.  When you say 
two-parameter, do you mean the real and imaginary part of the 
independent variable?  I guess you are right that I don't necessarily 
need to use the determinant.  In order to satisfy the boundary 
conditions of the problem this 4x4 or 6x6 matrix (which is really a 
submatrix of an 8x8 or 12x12) must have a null space.  So, what would be 
the better thing to look for?  An eignevalue that approaches 0?

Ryan

Nils Wagner wrote:

> Ryan Krauss wrote:
>
>> I have a matrix that is a function of a complex valued input.  I am 
>> trying to find that value of that input that drives the determinant 
>> of the matrix to zero.  I am searching for this value using fmin. The 
>> error I am trying to minimize is the abs(det(complex matrix)).
>
>
> It's not a good idea to use the determinant directly since det(A) is a 
> rapidly varying function. As far as I understand your problem,
> you are interested in the solution of a two-parameter nonlinear 
> eigenvalue problem. Is that correct ? How about the size of your 
> complex matrix A ?
>
> Nils
>
>> I don't seem to be able to drive this error lower that roughly 9e-17, 
>> regardless of the values for ftol and xtol I use.
>>
>> Am I hitting some internal limitation?  Are complex values by default 
>> single or double precision?
>>
>> Thanks,
>>
>> Ryan
>>
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>
>
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