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Cubic root finding on a grid [message #68737]

Fri, 20 November 2009 08:03

Luds
Messages: 7
Registered: September 2009

Junior Member

Hi IDL'ers,

I'm trying to find an efficient method for estimating the eigenvalues
of a tensor which is defined on a cubic (NxNxN) grid. The tensor is a
simple 3x3 (symmetric) matrix defined at each of the N^3 grid points,
so the eigenvalues at a given grid point can be calculated by (for
example) the IDL routine IMSL_ZEROPOLY simply by finding the roots of
the cubic polynomial defined by the matrix at that point - but this
routine doesn't handle array's of coefficients, so it has to be
evaluated on the grid point by point.

My grids are up to 512^3, so using a for-loop to compute the
eigenvalues at each node is rather slow. Does anyone know of any
adaptations of the IMSL_ZEROPOLY routine that can work on a grid of
3X3 matricies (or on an array of polynomial coefficients)?

Any suggestions would help.

Best,
Ludlow

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[Message index]

		Cubic root finding on a grid By: Luds on Fri, 20 November 2009 08:03
		Re: cubic root By: Lajos Foldy on Tue, 16 April 2013 09:44
		Re: cubic root By: wlandsman on Tue, 16 April 2013 08:27
		Re: cubic root By: Lajos Foldy on Tue, 16 April 2013 08:19

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