# Dr. Thomas Mach

Kontakt
Raum:
2.29.2.05
Telefon:
0331 977-230182

## Publikation @ Potsdam

2021 | New matrix function approximations and quadratue rules based on the Arnoldi process | Nasim Eshghi and Thomas Mach and Lothar ReichelZeitschrift: Journal of Computational and Applied MathematicsLink zur Publikation

### New matrix function approximations and quadratue rules based on the Arnoldi process

#### Autoren: Nasim Eshghi and Thomas Mach and Lothar Reichel (2021)

The Arnoldi process can be applied to inexpensively approximate matrix functions of the form f(A)v and matrix functionals of the form v∗(f(A))∗g(A)v, where A is a large square non-Hermitian matrix, v is a vector, and the superscript ∗ denotes transposition and complex conjugation. Here f and g are analytic functions that are defined in suitable regions in the complex plane. This paper reviews available approximation methods and describes new ones that provide higher accuracy for essentially the same computational effort by exploiting available, but generally not used, moment information.
Numerical experiments show that in some cases the modifications of the Arnoldi decompositions proposed can improve the accuracy of v∗(f(A))∗g(A)v about as much as performing an additional step of the Arnoldi process.

Zeitschrift:
Journal of Computational and Applied Mathematics