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midpoint-radius



Dear intervalers,

The enclosed paper presents and analyzes algorithms for
interval matrix multiplication. Conversion from infsup to
midrad representation is analyzed; also an optimal
algorithm is given. In particular

- Note that midrad matrix multiplication is significantly faster
(factor 50 to 200 for n=1000) than the traditional and our
Profil/Bias approach (Table 1.1).

- The proposed conversion of infsup to midrad in Section 5.2  in
the "Vienna proposal for interval standardization, Manuscript (2008)"
   set round up
   r = 0.5*(u-l);m=l+r.
is not correct (see the remark following Theorem 3.6 in my paper).

- The effect of overestimation in interval matrix multiplication is often
small in practical applications such as the solution of linear systems
(Section 5, in particular Table 5.10).

The article will appear in "Numerical Algorithms".

Best wishes,

Siegfried M. Rump

--
=====================================================
Prof. Dr. Siegfried M. Rump
Institute for Reliable Computing
Hamburg University of Technology
Schwarzenbergstr. 95
21071 Hamburg
Germany
phone +49 40 42878 3027
fax +49 40 42878 2489
http://www.ti3.tu-harburg.de

and

Visiting Professor at Waseda University
Faculty of Science and Engineering
3-4-1 Okubo, Shinjuku-ku
Tokyo 169-8555
Japan
phone/fax in Japan +81 3 5286 3330

Attachment: Ru11a.pdf
Description: Adobe PDF document