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  • libeigenlibeigen
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  • #1017

Householder transformation underflows for vectors with tiny norms.

Submitted by Christoph Hertzberg @chhtz

Assigned to Nobody

Link to original bugzilla bug (#1017)
Version: 3.3 (current stable)

Description

This seems to be the cause of eigensolver_selfadjoint_3 failing most of the time.
As far as I see what happens is that (in src/Householder/Householder.h) makeHouseholder is not robust to underflows, i.e. if c0!=0 && c0*c0==0 then
beta = sqrt(numext::abs2(c0) + tailSqNorm);
is slightly too small (especially if tailSqNorm is quite small as well).

Blocking

#661 #814 (closed)

Edited Feb 16, 2021 by Rasmus Munk Larsen
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