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ETNA - Electronic Transactions on Numerical Analysis
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Verlag der Österreichischen Akademie der Wissenschaften Austrian Academy of Sciences Press
A-1011 Wien, Dr. Ignaz Seipel-Platz 2
Tel. +43-1-515 81/DW 3420, Fax +43-1-515 81/DW 3400 https://verlag.oeaw.ac.at, e-mail: verlag@oeaw.ac.at |
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DATUM, UNTERSCHRIFT / DATE, SIGNATURE
BANK AUSTRIA CREDITANSTALT, WIEN (IBAN AT04 1100 0006 2280 0100, BIC BKAUATWW), DEUTSCHE BANK MÜNCHEN (IBAN DE16 7007 0024 0238 8270 00, BIC DEUTDEDBMUC)
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ETNA - Electronic Transactions on Numerical Analysis, pp. 179-196, 2017/11/15
Let $A\in\mathbb{R}^{p\times p}$ be a diagonalizable matrix and $f$ a smooth function.We are interested in the problem of approximatingthe action of $f(A)$ on a vector ${\bf b}\in\mathbb{R}^p$, i.e., $f(A){\bf b}$, without explicitlycomputing the matrix $f(A)$.In the present work, we derive families of one-term, two-term, and three-term inexpensive approximationsto the quantity $f(A){\bf b}$ via an extrapolation procedure.For a given diagonalizable matrix $A$,the proposed families of vector estimates allow us to approximate theform $W^Tf(A)U$, for any matrices $W,U\in\mathbb{R}^{p\times m}$, $1 \leq m \ll p$, not necessarily biorthogonal.We present several numerical examples to illustrate the effectivenessof our method for several functions $f$ for boththe quantity $f(A){\bf b}$ and the form $W^Tf(A)U$.
Keywords: f(A)b, vector estimates, vector moments, extrapolation, diagonalizable matrices