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# Singular at Working Precision

On Programmer » Matlab

888 words with 1 Comments; publish: Mon, 19 May 2008 00:42:00 GMT; (20078.13, « »)

From my perusal of this list, it appears that "Singular at

Working Precision" seems to be the favorite error message.

I am trying to solve a set of ill-specified equations Ax =

B, where A is

0. Large

1. Sparse

2. Symmetric

3. Full rank, and

4. Positive semidefinite

x = A\B gives me the dreaded "Singular at Working Precision"

warning.

Solving via chol() and backsubstitution seems to run out of

memory since A is large (nxn, n~200,000). Any suggestions?

Thanks,

John

*http://matlab.todaysummary.com/q_matlab_55736.html*

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- 1 Comments
- "John Smith" <spamalot.matlab.todaysummary.com.jhu.edu> wrote in message
<fka413$f7r$1.matlab.todaysummary.com.fred.mathworks.com>...

>

> x = A\B gives me the dreaded "Singular at Working Precision"

> warning.

>

What bother you? The warning message or the unsatisfied

solution x? If it's the later please elaborate.

Bruno

#1; Mon, 19 May 2008 00:43:00 GMT

- "John Smith" <spamalot.matlab.todaysummary.com.jhu.edu> wrote in message