[Dune] [#729] Singularity detection in FieldMatrix' LU decomposition buggy (Attachment added)

[Dune]

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User who did this - Andreas Lauser (andlaus) 

Attached to Project - Dune
Summary - Singularity detection in FieldMatrix' LU decomposition buggy
Task Type - Bug Report
Category - Common
Status - Unconfirmed
Assigned To - 
Operating System - Linux
Severity - Medium
Priority - Normal
Reported Version - SVN (pre2.0)
Due in Version - Undecided
Due Date - Undecided
Details - The singularity detection in the FieldMatrix' LU decompostion throws an exception for the following matrix

1, 0, 0, 0
-3.02852e-07, 1, -0.00434667, 1.08683e-09
 0, 0, 1, 0
 -4248.83, -9.22043e+09, 0, 1

This is due to the fact, that the ratio between the largest and the smallest entry is 18 decimal orders of magnitute which is above machine precision of about 16 orders of magnitute.

On the other hand, the matrix clearly isn't singular and it emerges naturally from a physical problem.

Disabling the singularity detection makes the LU decomposition (and my model) work without any problems, which is due to the fact that very large and very small numbers are never added during the course of the decomposition.


One or more files have been attached.

More information can be found at the following URL:
http://www.dune-project.org/flyspray/index.php?do=details&task_id=729

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