[Dottorcomp] seminario Marcus V. Sarkis Martins (Worcester Polytechnic Institute, USA), 24 Maggio 2023, ore 11:00, aula Beltrami

[Luca Franco Pavarino]

Cari Colleghi,

Mercoledì 24 Maggio 2023, alle ore 11:00 in aula Beltrami,
il Prof. Marcus V. Sarkis Martins (Worcester Polytechnic Institute, USA)
terrà un seminario dal titolo:

NOSAS: NOnoverlapping Spectral Additive Schwarz

Abstract: NOSAS is a family of adaptive Schwarz preconditioners designed
originally for solving elliptic problems with highly heterogeneous
coefficients. It has flavors from both overlapping and nonoverlapping
methods. Different from the overlapping methods, like GDSW and GeoEo, NOSAS
has no local problems on extended subdomains, and different from the
nonoverlapping methods, like BDD, BDDC, FETI and FETI-DP, NOSAS has no
weighting operator to average local solutions on the interface. In RASHO,
all the local factorizations and eigensolvers are done inside the
nonoverlapping subdomains, and like BDD the coarse degrees of freedom are
related to the bad nodes inside each of these subdomains, however, with a
better corresponding coarse stiffness in terms of sparsity. RASHO is very
flexible, can be designed to have condition number from (1 + log H/h)^2  to
(1 + H/h)^2 without solving any eigenvalue problem. Finally, RASHO is easy
to implement. In this talk we introduce the predecessor of NOSAS, the
Average Additive Schwarz Method introduced by Bjorstad and Dryja 99’, and
then move to the vanilla version of NOSAS and then to the adaptive
versions, economical versions and three-level versions. We show numerical
experiments and some comparisons with GeoEo and Adaptive BDDC.
This is a work in collaboration with Yu Yi and Maksymilian Dryja.

Tutti gli interessati sono invitati a partecipare. Cordiali saluti,

    Luca Pavarino
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