Re: Non-commutative algebra (Re: [eigen] On a flexible API for submatrices, slicing, indexing, masking, etc.)

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

On 23.12.2016 at 10:35, Peter wrote:
> That brings up a question, which may only concern my work.
> Does Eigen actually assume, that the floating point types are commuting?

We do at several points. E.g.
  s1 * A * s2 * B * s3
is optimized to something equivalent to
  (s1*s2*s3)*(A*B)

> I'm asking since I have a  programme that normalizes the input of an object
> we physicist call Hamiltonian and it consists of anti-commuting variables,
> i.e. a * b == -b * a . For examples it calculates commutators consisting of
> matrices containing these objects and simplifies the resulting expression.

You may be interested in this feature-request:
http://eigen.tuxfamily.org/bz/show_bug.cgi?id=560



Christoph





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