Article View: sci.math.num-analysis
Article #1153Re: Condition Number
From: W. Donald Rolph
Date: Tue, 12 Jan 1993 12:20
Date: Tue, 12 Jan 1993 12:20
20 lines
1433 bytes
1433 bytes
It is actually even more complex than just looking at the eignvalues. ONe must
also examine whether the eigenvectors of the ill conditioning are being excited.
It is a trivial example, but the largest positive definite ill conditioning on a
VAX in single precision is approximately 10E76. The following matirx is the
worst case conditioning, but is highly stable during Gauss elimination:
1.e38 0
A =
0 1.e-38
This effect is particularly noticable in thin shell problems using dinite element
analysis, since the out of plane eigenvectors are not excited by in plane
bending, evne though the ill conditioning is very high (frequently on the order
of 10e9).
--
Regards.
Don Rolph a722756@pan.mc.ti.com WD3 MS10-13 (508)-699-1263
Technical Details
Message-ID:
<1993Jan12.072055@roper.mc.ti.com>Path:
arc1-ca.pugleaf.net!sparky!uunet!zaphod.mps.ohio-state.edu!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!pan.mc.ti.com!a722756References:
<1993Jan11.083253.9521@dutrun2.tudelft.nl> <63332@mimsy.umd.edu>Show Full Headers
Complete Article Headers
Newsgroups: sci.math.num-analysis Path: arc1-ca.pugleaf.net!sparky!uunet!zaphod.mps.ohio-state.edu!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!pan.mc.ti.com!a722756 From: a722756@roper.mc.ti.com (W. Donald Rolph) Subject: Re: Condition Number Message-ID: <1993Jan12.072055@roper.mc.ti.com> Originator: a722756@roper.mc.ti.com Sender: usenet@pan.mc.ti.com (USENET News System) Organization: Texas Instruments / Attleboro Mass / USA References: <1993Jan11.083253.9521@dutrun2.tudelft.nl> <63332@mimsy.umd.edu> Date: Tue, 12 Jan 1993 12:20:55 GMT Lines: 20