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This site provides a central location for information about the INFORMS Student Chapter at CMU.

In particular, you will see abstracts of upcoming talks for our student seminar. The seminar is currently (Spring 2015) organized by Aleksandr Kazachkov and Christian Tjandraatmadja. Please contact them if you are interested in giving a talk.

In Spring 2015, talks will usually be on Mondays at 6:30pm, but may be arranged on special days depending on speaker availability.

For more info, see the announcements below or on the Quick Calendar in the sidebar.


3/2/15 - Monday discussion dinner with Christian Tjandraatmadja

posted by Aleksandr Kazachkov

WHEN: 3/2/15, 6:30pm

WHERE: Posner 384

DETAILS:
We will be hosting the Monday Discussion Dinner in Room 384 of 
Posner Hall (Tepper) at 6:30pm (NOTE THE ROOM CHANGE). Our main speaker will be Christian Tjandraatmadja whose topic will be "Aiming and Shooting: Thoughts on an Empirical Exploration of Facets".

If you'd like to join and order food, please fill out the order form by 5pm today at the latest:

http://goo.gl/forms/urmbYT3QIu

Hope to see you there!

===
Deadline for food orders: 5:00pm the day of the dinner

Every week we get together to eat food and talk about interesting problems.
One person nominates themselves to talk about an idea they are thinking about, or a problem they think is interesting while we eat dinner together.

This is designed to be a casual and friendly environment for students to bounce ideas off others. 

Faculty are very welcome to attend and contribute!

2/23/15 - Monday discussion dinner with Aleksandr Kazachkov

posted Feb 23, 2015, 10:32 AM by Aleksandr Kazachkov   [ updated Feb 23, 2015, 10:32 AM ]

WHEN: 2/23/15, 6:30 pm

WHERE: Posner 388

DETAILS:
We will be hosting the Monday Discussion Dinner in Posner 388. Our main speaker today will be Aleksandr Kazachkov who will be talking about talking about algorithms, complexity results, and open problems in Vertex Enumeration.

If you'd like to join and order food, please fill out the order form by 5pm today at the latest:

http://goo.gl/forms/urmbYT3QIu

Hope to see you there!

===
Deadline for food orders: 5:00 pm

Every week we get together to eat food and talk about interesting problems.
One person nominates themselves to talk about an idea they are thinking about, or a problem they think is interesting while we eat dinner together.

This is designed to be a casual and friendly environment for students to bounce ideas off others. 

Faculty are very welcome to attend and contribute!

2/16/15 - General meeting and pizza social

posted Feb 12, 2015, 12:10 PM by Aleksandr Kazachkov

WHEN: Monday, 2/16/15 at 6:30pm

WHERE: Posner 388 (take the elevator in Posner [not GSIA] to the third floor and it will be to the left, around the corner)

DETAILS:
This is a general meeting and pizza social. In the meeting portion, we will discuss the events planned for this semester and take suggestions for the future. This social is open to anyone at Carnegie Mellon who is interested in INFORMS-related activities, regardless of sub-discipline or particular focus area. Come meet other students all across campus with similar interests!

2/13/15 - Review for Schmidt talk

posted Feb 11, 2015, 1:41 PM by Christian Tjandraatmadja

WHEN: February 13, 2015, 11:00am

WHERE: Posner 388

DETAILS:
On Friday, February 13, Daniel Schmidt (University of Cologne, visiting at Carnegie Mellon University) will be giving a talk. The seminar will start at 1:30pm in GSIA 322. We will meet at 11:00am to discuss some necessary background that will hopefully help us better understand the talk.

Please glance through the paper in advance, and we will work through any particular questions together. The paper can be found here: http://www.optimization-online.org/DB_HTML/2015/02/4763.html

===
Seminar information:

Name:  Daniel Schmidt

University:  University of Cologne visiting at Carnegie Mellon University

Date:  February 13, 2015

Time: 1:30 to 3:00 pm

Location:  Faculty Conference Room 322

Title:  Robust Network Design with a Single-Commodity and Uncertain
Demands

Abstract:  Given a set of sites with potential links, a cost function and
traffic requirements, Network Design is the task to find minimum cost
capacities for the links such that all traffic requirements can be met.
Unfortunately, network traffic is very hard to predict and varies
substantially. At the same time, locally insufficient network capacity can
lead to the breakdown of the entire network. This has led to the
development of Robust Network Design methods that can include different
traffic scenarios in the optimization process.

In this talk, we consider such a method in the form of an exact branch-
and-cut algorithm. It computes robust solutions for a network design
problem that is based on a single-commodity flow. We show a cut-based
integer linear programming formulation that allows us to specify the set
of traffic scenarios as both a finite list and as a feasible region of a
set of linear inequalities. We show cut-separation procedures for both
cases and give additional 3-partition inequalities that further strengthen
our formulation. These additional inequalities can be separated as Zero-
Half-Cuts. Computational results show the effectiveness of the approach.

2/9/15 - Monday discussion dinner with Thiago Serra

posted Feb 9, 2015, 7:25 AM by Aleksandr Kazachkov

WHEN: 2/9/15, 6:30 pm

WHERE: Tepper PhD Lounge

DETAILS:
We will be hosting the Monday Discussion Dinner in the Tepper PhD lounge (room 201) at 6:30. Our main speaker today will be Thiago Serra who will be talking about Disjunctive Cuts.  If you would like to join and order food, please fill out the order form by 5pm today at the latest:

http://goo.gl/forms/PMWB6Bw4x4

Hope to see you there!

===
Deadline for food orders: 5:00 pm

Every week we get together to eat food and talk about interesting problems.
One person nominates themselves to talk about an idea they are thinking about, or a problem they think is interesting while we eat dinner together.

This is designed to be a casual and friendly environment for students to bounce ideas off others. 

Faculty are very welcome to attend and contribute!

2/2/15 - Monday discussion dinner with Ryo Kimura

posted Feb 5, 2015, 9:54 AM by Aleksandr Kazachkov   [ updated Feb 5, 2015, 9:55 AM ]

WHEN: 2/2/15, 6:30 pm

WHERE: Tepper PhD Lounge

DETAILS:
We will be hosting our third Monday Discussion Dinner in the Tepper PhD lounge (room 201) at 6.30. Our main speaker today will be Ryo Kimura who will be talking about Petri Nets.  If you would like to join and order food, please fill out the order form by 5pm today at the latest:

http://goo.gl/forms/PMWB6Bw4x4

Hope to see you there!

===
Deadline for food orders: 5:00 pm

Every week we get together to eat food and talk about interesting problems.
One person nominates themselves to talk about an idea they are thinking about, or a problem they think is interesting while we eat dinner together.

This is designed to be a casual and friendly environment for students to bounce ideas off others. 

Faculty are very welcome to attend and contribute!

1/26/15 - Monday discussion dinner with Vince Slaugh

posted Jan 26, 2015, 7:06 AM by Aleksandr Kazachkov   [ updated Jan 26, 2015, 10:56 AM ]

WHEN: 1/26/15, 6:30 pm

WHERE: Posner 205

DETAILS:
We will be hosting our second Monday Discussion Dinner in room 205 (Tepper) at 6.30. Our main speaker today will be Vince Slaugh. If you would like to join and order food, please fill out the order form by 5pm today at the latest:

http://goo.gl/forms/PMWB6Bw4x4

Hope to see you there!

===
Deadline for food orders: 5:00 pm

Every week we get together to eat food and talk about interesting problems.
One person nominates themselves to talk about an idea they are thinking about, or a problem they think is interesting while we eat dinner together.

This is designed to be a casual and friendly environment for students to bounce ideas off others. 

Faculty are very welcome to attend and contribute!

1/19/15 - Monday discussion dinner with Tarek Elgindy

posted Jan 26, 2015, 7:03 AM by Aleksandr Kazachkov   [ updated Jan 26, 2015, 10:57 AM ]

WHEN: 1/19/15, 6:30 pm

WHERE: PhD lounge

DETAILS:
We will be hosting the inaugural Monday Discussion Dinner in the Tepper PhD lounge at 6:30. Tarek Elgindy will be talking about stochastic network design problems. Other research topics are also welcome to discuss. If you'd like to join and order food, please fill out the order form by 5pm today at the latest:

http://goo.gl/forms/hwO5rOFVNj

Hope to see you there!

===
Deadline for food orders: 5:00 pm

Every week we get together to eat food and talk about interesting problems.
One person nominates themselves to talk about an idea they are thinking about, or a problem they think is interesting while we eat dinner together.

This is designed to be a casual and friendly environment for students to bounce ideas off others.

Faculty are very welcome to attend and contribute!

12/5/14 - Review for Margot talk

posted Dec 3, 2014, 8:33 AM by Christian Tjandraatmadja

WHEN: 12/5/14, 12:00pm

WHERE: GSIA 227

DETAILS:
On Friday, December 5, François Margot (CMU Tepper School of Business) will be giving a talk. The seminar will start at 1:30pm in GSIA 322. We will meet at 12:00pm to discuss some necessary background that will hopefully help us better understand the talk. Bring your own lunch!

Please read or glance through the paper in advance, and we will work through any particular questions together. The paper can be found here: http://link.springer.com/chapter/10.1007%2F978-3-319-07557-0_15

===
Title: Cut Generation through Binarization

Abstract:  Cutting planes (or cuts) are an essential component of state-of-the-art solvers for Mixed-Integer Linear Program (MILP). Among the many classes of cuts, split cuts are one of the most useful and essential. It is known that split cuts are able to close a large part of the integrality gap for usual benchmark instances, but this requires a large cpu time.

Empirical split cut generation aims at generating fast the most useful split cuts. Advances in this direction usually focus on finding strong disjunctions, involving several variables. In this talk, our aim is to use combinations of simple split cuts, i.e. cuts obtained using disjunctions of the form x_j = 0 or x_j = 1 for a binary variable x_j to generate cuts that have similar strength as general split cuts. Our cut generation scheme is based on two components. First, we use a binarization of general integer variables (i.e., replacing a general integer variable by a sum of binary variables), augmented by additional symmetry breaking constraints. This binarization was introduced by Roy for generating strong Lift-and-Project cuts. Second, we use rank-2 simple-split cuts, i.e., cuts that can be obtained as a simple split cut for a polyhedron obtained by adding all simple split cuts for the binarization of the problem. We show that for a pure integer problem with two integer variables, these cuts are sufficient to obtain the integer hull of the problem, but that this does not generalize to problems in higher dimensions. We also give an algorithm to compute an approximation of the rank-2 simple split cut closure. We report empirical results on 22 benchmark instances showing that the bounds obtained compare favorably with those obtained with other approximate methods to compute the split closure or lattice-free cut closure. It gives a better bound than the split closure on 6 instances while it is weaker on 9 instances, for an average gap closed 3.8\% smaller than the one for the split closure.

Join work with Pierre Bonami, IBM ILOG CPLEX.

10/24/14 - Review for Basu talk

posted Oct 22, 2014, 8:40 AM by Christian Tjandraatmadja   [ updated Oct 22, 2014, 8:41 AM ]

WHEN: 10/24/14, 9:30am

WHERE: GSIA 227

DETAILS:
On Friday, October 24, Amitabh Basu (John Hopkins University) will be giving a talk. The seminar will start at 1:30pm in Posner 151. We will meet at 9:30am in GSIA 227 to discuss some necessary background that will hopefully help us better understand the talk.

Please read or glance through the paper in advance, and we will work through any particular questions together. The paper can be found here:
http://arxiv.org/abs/1410.1571.

===
Title:  On the covering property of the lifting region

Abstract:  We will present recent progress on the connections between cut-generating functions and covering/tiling properties of subsets of euclidean sets. Important structural information about strong cut-generating functions can be translated to geometric questions like: Does a particular compact subset X of R^n cover all of R^n when we consider all of it translates by integer vectors? This connects to very classical problems in the geometry of numbers and deep theorems like the Venkov-Alexandrov-McMullen theorem on tilings, and the geometry of zonotopes can be leveraged. Research in this area of integer optimization is very much work-in-progress; we will close the presentation with an invitation to join our quest with some open problems.

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