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Friday, November 3, 2017 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Laurent Poirrier

Title: How we solve linear programs

Speaker: Laurent Poirrier
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

Linear programming is one of the most fundamental tools in optimization, and its theoretical complexity is well understood. In practice though, things are quite different: Which types of problems can we really solve? What sizes? With what algorithms?

Wednesday, November 8, 2017 4:00 pm - 4:00 pm EST (GMT -05:00)

Continuous Optimization Seminar - Nargiz Kalantarova

Title: A Fast Iterative Shrinkage-Thresholding Algorithm for Linear Inverse Problems 

Speaker: Nargiz Kalantarova
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

We will be discussing the paper (having the same title) by Amir Beck and Marc Teboulle. We consider the class of iterative shrinkage-thresholding algorithms (ISTA) for solving linear inverse problems arising in signal/image processing. This class of methods, which can be viewed as an extension of the classical gradient algorithm, is attractive due to its simplicity and thus is adequate for solving large-scale problems even with dense matrix data.

Thursday, November 9, 2017 3:30 pm - 3:30 pm EST (GMT -05:00)

Algebraic Graph Theory Seminar - Harmony Zhan

Title: An Introduction to Discrete Quantum Walks

Speaker: Harmony Zhan
Affiliation: University of waterloo
Room: MC 6486

Abstract:

We will introduce the concept of a discrete quantum walk, prove some of its properties, discuss its relation to different graph structures, and construct interesting walks from these structures such as self-dual embeddings.

Thursday, November 9, 2017 3:30 pm - 3:30 pm EST (GMT -05:00)

Graphs and Matroids Seminar - Ben Moore

Title: An application of graph "recolouring”

Speaker: Ben Moore
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

I will prove that for any graph G, if there is an edge e such that G-e has less than (k-1)!/2 cycles of length zero mod k, then the chromatic number of G is less or equal to k.

Friday, November 10, 2017 3:30 pm - 3:30 pm EST (GMT -05:00)

Tutte Colloquium - Shenwei Huang

Title: Coloring (cap even hole)-free graphs

Speaker: Shenwei Huang
Affiliation: Wilfrid Laurier University
Room: MC 5501

Abstract:

An even cycle of length 4 or more is called an even hole. A cap is a cycle of length at least 5 with exactly one chord and that chord creates a triangle with the cycle. In this talk we consider (cap, even hole)-free graphs, i.e., graphs that do not contain any even hole or cap as an induced subgraph.

Wednesday, November 15, 2017 4:00 pm - 4:00 pm EST (GMT -05:00)

Continuous Optimization Seminar - Stefan Sremac

Title: Proximal alternating linearized minimization for nonconvex and nonsmooth problems

Speaker: Stefan Sremac
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

We will be discussing the paper (having the same title) by Jerome Bolte, Shoham Sabach and Marc Teboulle.  We introduce a proximal alternating linearized minimization (PALM) algorithm for solving a broad class of nonconvex and nonsmooth minimization problems.

Thursday, November 16, 2017 3:30 pm - 3:30 pm EST (GMT -05:00)

Algrbraic Graph Theory Seminar - Chris Godsil

Title: Constructing cospectral graphs with a different switching

Speaker: Chris Godsil
Affiliation: University of Waterloo
Room: MC 6486

Abstract:

Many years ago, Brendan McKay and I introduced a construction of pairs of cospectral graphs, sometimes known as local switching. In the same paper we introduced a second switching technique which produces, as special cases, the smallest pair of cospectral graphs and the smallest pair of connected cospectral graphs.

Thursday, November 16, 2017 3:30 pm - 3:30 pm EST (GMT -05:00)

Graphs and Matroids Seminar - Bruce Richter

Title: Convex drawings of complete graphs:  topology meets geometry

Speaker: Bruce Richter
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

A drawing D of the complete graph K(n) is the sphere is characterized by, for each isomorph J of K(5), D[J] is homeomorphic to one of the three rectilinear drawings of K(5).  Every drawing of K(n) in the plane with all edges straight-line segments is obviously convex.  Thus, convex drawings generalize planar point sets that are in general position. 

Friday, November 17, 2017 3:30 pm - 3:30 pm EST (GMT -05:00)

Tutte Colloquium - Simon Lacoste-Julien

Title: Recent Advances in Frank-Wolfe Optimization

Speaker: Simon Lacoste-Julien
Affiliation: University of Montreal
Room: MC 5501

Abstract:

The Frank-Wolfe (FW) optimization algorithm has lately re-gained popularity thanks in particular to its ability to nicely handle the structured constraints appearing in machine learning and signal processing applications. However, its convergence rate is known to be slow (sublinear) when the solution lies at the boundary.

Wednesday, November 22, 2017 4:00 pm - 4:00 pm EST (GMT -05:00)

Continuous Optimization Seminar - Henry Wolkowicz

Title: Alternating Direction Method of Multipliers for the SDP Relaxation of the Quadratic Assignment Problem

Speaker: Henry Wolkowicz
Affiliation: University of waterloo
Room: MC 5479

Abstract:

The semidefinite programming (SDP) relaxation has proven to be extremely strong for many hard discrete optimization problems. This is in particular true for the quadratic assignment problem (QAP), arguably one of the hardest NP-hard discrete optimization problems.