Detecting Matlab failure to solve sparse linear system

Question

I want to programmatically find out when A\b failed (for sparse A) so that I can run some problem-specific logic. Using the backslash operator

A\b

I get warnings printed to the console but I want to know about these conditions (singular or nearly singular) programmatically so I can do some problem-specific stuff.

For dense systems, I can do

[soln, cond_recip] = linsolve(A,b);
if cond_recip < 1e-15, ..., end

But linsolve does not work for sparse matrices and I do not want to densify my matrices.

Amro · Accepted Answer · 2013-04-26 15:37:32Z

1

Try the following:

%# temporarily set warning to issue errors (maybe there are others?)
s = warning('error', 'MATLAB:nearlySingularMatrix'); %#ok<CTPCT>

try
    x = magic(4)\[34; 34; 34; 34];
catch ME
    disp(ME.message)
    %#.. problem specific stuff..
end

%# restore warning state
warning(s);

answered Apr 26, 2013 at 15:37

Amro

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1 Comment

Amro Over a year ago

I learned of this trick from: undocumentedmatlab.com/blog/trapping-warnings-efficiently

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