Dyrektor Instytutu Informatyki - dr hab. inż. Jan Sadecki, serdecznie zaprasza na seminarium, które odbędzie się: 11 grudnia (wtorek) 2018 r. o godzinie  13.00  w sali  P3-109

Prelegenci oraz tematy referatów:

godz. 13.00:   Prof. Walter Gander: “MATRIX COMPLETION WITH EPSILON-ALGORITHM”

godz. 14.00:   Prof. Veikko Keranen: “COMBINATORICS ON WORDS AND COMPUTATIONAL STRUCTURES”

godz. 15.00:   Prof. Krystyna Zietak: “ON a SUB-STIEFEL PROCRUSTES PROBLEM”

 


 

Prof. Dr. Water Gander, Swiss Federal Polytechnic Institute in Zurich, Switzerland

RESEARCH TALK: MATRIX COMPLETION WITH EPSILON-ALGORITHM

Abstract:

We show how the convergence of an algorithm for matrix completion can be significantly improved by applying Wynn's epsilon-algorithm. Straightforward generalization of the scalar epsilon-algorithm to matrices fails. However, accelerating the convergence of only the missing matrix elements turns out to be very successful.

Expected time ~ 60 min.

 


 

Prof. Dr. Veikko Kerannen, Lapland University, Rovaniemi, Finland

RESARCH TALK: COMBINATORICS ON WORDS AND COMPUTATIONAL STRUCTURES

Abstract:

We discuss the long-lasting extensive research from 1990 to the present on abelian pattern avoidance in words. Paul Erdös posed the original problem in 1961, and, in 1992, we found a solution to the remaining open problem on four letters. We also present history of combinatorics on words research, many applications of the results, and the needed intensive computations using different computing paradigms. A related open problem on three letters is introduced. Finding a solution to it has turned out elusive. The problem may even be undecidable. The involved computer experiments have lead to remarkably complex and counter-intuitive phenomena, and to generation of extreme events and extremely fragile structures. The field has also connections to bioinformatics, including DNA/RNA mutations and hypohelix structures.

Expected time ~ 45 min

 


 

Prof. Dr. Krystyna Zietak, Wroclaw University of Technology, Poland

RESARCH TALK: ON a SUB-STIEFEL PROCRUSTES PROBLEM

Abstract:

In the talk we  consider  a Procrustes problem on the set of sub-Stiefel matrices. A sub-Stiefel matrix is a matrix that results from deleting simultaneously the last row and the last column of an orthogonal matrix. An iterative algorithm for computing the solution of the sub-Stiefel Procrustes problem is proposed. For these purposes we investigate  the properties of sub-Stiefel matrices. We also relate the sub-Stiefel Procrustes problem with the Stiefel Procrustes problem and compare it with the orthogonal Procrustes problem.

Expected time ~ 45 min.