The McCombs School of Business

IROM Department

What is Operations Research and Operations Management?:

OR/OM is a science (or profession?) that uses mathematical and qualitative tools to describe, model and solve real life problems. That sounds very broad. Here some successful stories.

INFORMS Institute for Operations Research and the Management Sciences

ICHIO Instituto Chileno de Investigación Operativa.

The Operations Room blog

Michael Trick's blog

Others:

chilebonito.cl

A project that I have with my brother (he has done almost everything, though). It is a work in progress.

"We are a community that seeks to encourage and promote tourism in Chile through our own experiences in those places where we were lucky enough to know or live."

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How bikes can save us

Since 2005, Chile’s professional soccer league has used a game-scheduling system based on an integer linear programming model. The Chilean league managers have considered several criteria for the last tournaments’ scheduling, involving operational, economic and sporting factors, thus generating a highly constrained problem, in practice unsolvable by their last methodology. This led to the adoption of a model with real conditions, some of them totally new in the use of sports scheduling techniques in soccer leagues. The schedules so obtained have meant greater benefits for the teams, given by lower costs and higher incomes, fairer seasons and tournaments that are more attractive to sports fans. Such success has completely fulfilled the expectations of the Asociación Nacional de Fútbol Profesional (ANFP), the organizing body for Chilean professional soccer.

We consider the problem of dispatching technicians to service/repair geographically distributed equipment. This problem can be cast as a vehicle routing problem with time windows, where customers expect fast response and small delays. Estimates of the service time, however, can be subject to a significant amount of uncertainty due to misdiagnoses of the reason for failure or surprises during repair. It is therefore crucial to develop routes for the technicians that would be insensitive to substantial deviations from estimated service times.  In this paper we propose a robust formulation for vehicle routing problem with soft time windows and service time uncertainty. We present exact formulations and a column generation algorithm to solve it capable of solving real world sized instances. We evaluate the efficiency of the approach through computational experiments on real industry routing data.

In this paper we propose a Branch and Price scheme to solve a joint depot location, fleet design and routing problem, required for the application of the standardized evaluation exam SIMCE over all schools located in Santiago-Chile. This exam is conducted every year by the Ministry of Education. The master problem is an extension of a standard VRP, while the resulting subproblem is faced with Constraint Programming.

We consider a real problem faced by the repair services of Xerox in Santiago, Chile. In a typical day about twenty technicians visit seventy customers on a predefined service area in Santiago. The problem is modeled by considering travel times, soft time windows in technician arrival times at client locations and fixed repair times to design optimally routes for technicians. A Branch and Price algorithm was developed, using a constraint branching strategy proposed by Ryan and Foster along with Constraint Programming in the column generation phase. The column generation takes advantage of the fact that each technician can visit no more than five to six service requests per day. The problem was solved to optimality in reasonable computer time. Results obtained compare favorably with current practice.