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University of Colorado at Denver

Optimization Seminar

Fall 1997

The Optimization Seminar is held every Tuesday from 12:00-1:30 pm in Room 626 of the CU-Denver Bldg. at the corner of Lawrence and 14th Streets (just across Speer Blvd. from the Auraria campus). Anyone with an interest in optimization is invited to attend. Refreshments are provided.

To get on our mailing list, send email to Prof. Stephen Billups.

For more information about optimization at CU-Denver, visit our optimization community

Next Talk


The Expected Time for a Widely Used Min-Plus Algebra Algorithm is Infinite




Dave Fisher
University of Colorado at Denver
Department of Mathematics

Tuesday, Dec. 2, 1997, 12:00 noon
CU-Denver Bldg., Room 626


ABSTRACT:

In min-plus algebra, minimization replaces addition, and addition replaces multiplication. For example, let A be the matrix
                                    2 0 2
                                A = 4 2 3
                                    3 0 3
By iterating A^n = A A^{n-1} where matrix multiplication is done in min-plus algebra, we get
                    4 2 3            6 3 5           7 5 6
              A^2 = 6 3 5      A^3 = 7 5 6     A^4 = 9 6 8
                    4 2 3            6 3 5           7 5 6
Note A^4 = 3 A^2 (using "scalar addition") allowing us to conclude that A^n= 3 A^(n-2) for all n >= 4. It can be shown that we can always find a recursion with this procedure.

How long does it take to find a recursion? In many applications, the recursion is found with only a few matrix multiplications (sublinear in the matrix size). However when coefficients of a 2x2 matrix are chosen from a uniform distribution, the expected time to find a recursion is infinite.

This talk will start with an introduction to Min-Plus Algebra (with several applications) and conclude with calculations verifying the title result.


Fall Schedule

The following is the most recent schedule for the semester. If you are listed as a speaker, please double check to make sure that your scheduled date is acceptable. To see the abstract for a particular talk, click on the title of that talk.

Date Speaker/Leader Title/TopicMore info
Sept. 2 Steve Billups Organizational Meeting  
Sept. 9 Mark S. Gordon "Geometry Optimizations in Quantum Chemistry" 
Sept. 16 Marcus Emsermann and Allen Holder Brainstorming Session on Stochastic Linear Programming abstract in postscript format
Sept. 22(Monday)Vladimir Janovsky Qualitative Analysis of Newton's MethodJoint with CCM Colloquium
Monday, noon, room 656
Sept. 30Stephen Billups Overview of the PATH Solver--Winner of the Beale-Orchard-Hays Prize for Excellence in Computational Mathematical Programming  
Oct. 7 Harvey Greenberg "Post-solution Analysis in Mixed Integer Programming and Combinatorial Optimization" For full paper, click here. Joint with Discrete Math Seminar
Time: 2 p.m., Room 656
Oct. 14 Burt Simon A New Stochastic Procedure for Finding Roots of Systems of Unknown Functions Postscript version
Oct. 21Col. Greg Whaley NSA Summer Program for Operations Research Technology  
Oct. 28Allen Holder Positive Semidefinite Programming  
Nov. 4Marcus Emsermann Properties of the Expected Recourse Function in Two-Stage Recourse Stochastic Linear Programs  
Nov. 11 David Jamison Possibility theory as a method of incorporating model uncertainty into optimization problems.  
Nov. 18 David Jamison Possibility theory as a method of incorporating model uncertainty into optimization problems (cont)  
Nov. 25Tolya Puhalskii A critically loaded multirate link with trunk reservation  
Dec. 2 Dave Fisher The Expected Time for a Widely Used Min-Plus Algebra Algorithm is Infinite  
If you would like to give a talk, or have a topic you would like to see discussed, please send an email to Prof. Stephen Billups.


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Last updated: Oct. 8, 1997