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flow pass a cylinder with Reynolds number 200. The simulation was done using the augmented immersed interface method.
TALKS AND EVENTS
Numerical Analysis Seminar
Upcoming Events


Monday, March 6, 2017 at 3:00 PM in SAS 4201
Takeshi Ogita , Tokyo Womans Christian University
Takeshi Ogita , Tokyo Womans Christian University
A preconditioning method for dense linear systems

This talk is concerned with accurate numerical solutions
of ill-conditioned dense linear systems. Recently, we have
developed some preconditioning methods for this purpose.
Using such preconditioned methods, the condition number
of the coefficient matrices can be reduced sufficiently.
However, computational cost for such a preconditioning is
considerably larger than the standard numerical algorithm
such as LU factorization, since high-precision matrix
multiplication is required. In this talk, we modify this
point by exploiting the structure of the coefficient
matrix and develop an efficient algorithm for solving
ill-conditioned linear systems in high accuracy.
As a result, computational cost for preconditioning can
be significantly reduced with similar quality to the
previous methods. Numerical results are presented
showing the performance of the algorithm.

Monday, March 6, 2017 at 3:30 PM in SAS 4201
Siegfried M. Rump, Hamburg Technical University and Waseda University, Tokyo
Siegfried M. Rump, Hamburg Technical University and Waseda University, Tokyo
Reproducible summation, error-free transformations, and floating-point error estimates

Recently, reproducible summation gained much interest. The main problem is the lack of associativity of floating-point addition. One possibility to attack the problem is to compute without error, for example using error-free transformations. Some algorithms to that end will be presented. In a second part we will show new and improved error estimates for floating-point summation. As a new result, we completely refrain from using some floating-point grid. In contrast, we treat perturbed real sums, i.e., each individual addition is somehow perturbed, where there is almost no restriction on the size or kind of the perturbations. Nevertheless, we can avoid higher order terms in the error estimates.

Tuesday, March 14, 2017 at 3:00 PM in SAS 4201
Dirk Lorenz, TU Braunschweig
Dirk Lorenz, TU Braunschweig
TBA

TBA



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