18 research outputs found
Pipage Rounding, Pessimistic Estimators and Matrix Concentration
Pipage rounding is a dependent random sampling technique that has several interesting properties and diverse applications. One property that has been particularly useful is negative correlation of the resulting vector. Unfortunately negative correlation has its limitations, and there are some further desirable properties that do not seem to follow from existing techniques. In particular, recent concentration results for sums of independent random matrices are not known to extend to a negatively dependent setting.
We introduce a simple but useful technique called concavity of pessimistic estimators. This technique allows us to show concentration of submodular functions and conc
On a generalization of iterated and randomized rounding
We give a general method for rounding linear programs that combines the
commonly used iterated rounding and randomized rounding techniques. In
particular, we show that whenever iterated rounding can be applied to a problem
with some slack, there is a randomized procedure that returns an integral
solution that satisfies the guarantees of iterated rounding and also has
concentration properties. We use this to give new results for several classic
problems where iterated rounding has been useful
On a generalization of iterated and randomized rounding
We give a general method for rounding linear programs that combines the commonly used iterated rounding and randomized rounding techniques. In particular, we show that whenever iterated rounding can be applied to a problem with some slack, there is a randomized procedure that returns an integral solution that satisfies the guarantees of iterated rounding and also has concentration properties. We use this to give new results for several classic problems such as rounding column-sparse LPs, makespan minimization on unrelated machines, degree-bounded spanning trees and multi-budgeted matchings
The Expected Norm of a Sum of Independent Random Matrices: An Elementary Approach
In contemporary applied and computational mathematics, a frequent challenge
is to bound the expectation of the spectral norm of a sum of independent random
matrices. This quantity is controlled by the norm of the expected square of the
random matrix and the expectation of the maximum squared norm achieved by one
of the summands; there is also a weak dependence on the dimension of the random
matrix. The purpose of this paper is to give a complete, elementary proof of
this important, but underappreciated, inequality.Comment: 20 page