is there a vector cross product function?

Brian Gough bjg@network-theory.co.uk
Tue Mar 9 14:53:00 GMT 2004


linas@austin.ibm.com writes:
 > You can compute the cross-product for n-dimensional vectors, its
 > called the alternating product. Brian knows this, Britton may not.
 > 
 > Maybe its time for a gsl_tensor framework?

There is a tensor directory on the tensor-1-3 branch in the gsl cvs
repository on savannah.gnu.org, written by Jordi Burguet Castell.

It is a tricky problem though, in my opinion.

The approach there uses the correct type of struct, but I feel it
needs to use arrays instead of varargs for passing the n-dimensional
arguments in and out.  

The remaining unsolved issue is coming up with nice handling of views
and mappings to matrices and vectors.  Without this the tensors can't
interact with the rest of the linear algebra routines, which reduces
their usefulness significantly in practice.  A major design decision
is whether or not the tensor should allow physical sizes different
from the tensor size itself (i.e. LDA vs N in BLAS/LAPACK
terminology).  This has always been unclear to me.

-- 
Brian



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