Factorization of banded permutations
نویسندگان
چکیده
منابع مشابه
Permutations in the factorization of simplex bases
The basis matrices corresponding to consecutive iterations of the simplex method only differ in a single column. This fact is commonly exploited in current LP solvers to avoid having to compute a new factorization of the basis at every iteration. Instead, a previous factorization is updated to reflect the modified column. Several methods are known for performing the update, most prominently the...
متن کاملA transposition factorization of walk-permutations in graphs
Let G be a graph, e, , . . . . e, E E(G) edges, u1 , . . . . u,, oi, . . . . u, E V(G) vertices, such that (ui, vi) are the ends of ei, 1 < i < n. We follow the notations and definitions of [l, p. 121, but with a slight change in the notations of a walk: The sequence w=e,...e,~(u,e,u,)(~~e~u~)...(~~e~u,) is a walk if and only if vi = ui + i, 1~ i < IZ 1. In that case we also denote ~n=%+l~ and ...
متن کاملCounting permutations and polynomials with a restricted factorization pattern
We determine the asymptoti probability that a polynomial of degree n over a nite eld with q elements has no more than k irredu ible fa tors of any degree, for ea h natural number k. In parti ular we show that when q is large, almost 90% of su h polynomials have no more than 2 irredu ible fa tors of any given degree and almost 98% have no more than 3 irredu ible fa tors of any given degree. Simi...
متن کاملAsymptotic properties of the QR factorization of banded Hessenberg-Toeplitz matrices
We consider the Givens QR factorization of banded Hessenberg-Toeplitz matrices of large order and relatively small bandwidth. We investigate the asymptotic behavior of the R factor and the Givens rotation when the order of the matrix goes to infinity, and present some interesting convergence properties. These properties can lead to savings in the computation of the exact QR factorization and gi...
متن کاملGroups of banded matrices with banded inverses
AproductADF1 : : : FN of invertible block-diagonalmatrices will be bandedwith a banded inverse. We establish this factorization with the numberN controlled by the bandwidthsw and not by the matrix size n:When A is an orthogonal matrix, or a permutation, or banded plus finite rank, the factors Fi have w D 1 and generate that corresponding group. In the case of infinite matrices, conjectures rema...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Proceedings of the American Mathematical Society
سال: 2012
ISSN: 0002-9939,1088-6826
DOI: 10.1090/s0002-9939-2012-11411-x