165 research outputs found
Complexity of matrix problems
In representation theory, the problem of classifying pairs of matrices up to
simultaneous similarity is used as a measure of complexity; classification
problems containing it are called wild problems. We show in an explicit form
that this problem contains all classification matrix problems given by quivers
or posets. Then we prove that it does not contain (but is contained in) the
problem of classifying three-valent tensors. Hence, all wild classification
problems given by quivers or posets have the same complexity; moreover, a
solution of any one of these problems implies a solution of each of the others.
The problem of classifying three-valent tensors is more complicated.Comment: 24 page
Improved method for finding optimal formulae for bilinear maps in a finite field
In 2012, Barbulescu, Detrey, Estibals and Zimmermann proposed a new framework
to exhaustively search for optimal formulae for evaluating bilinear maps, such
as Strassen or Karatsuba formulae. The main contribution of this work is a new
criterion to aggressively prune useless branches in the exhaustive search, thus
leading to the computation of new optimal formulae, in particular for the short
product modulo X 5 and the circulant product modulo (X 5 -- 1). Moreover , we
are able to prove that there is essentially only one optimal decomposition of
the product of 3 x 2 by 2 x 3 matrices up to the action of some group of
automorphisms
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