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function c = cheap_condest (d, fail_if_singular)
%CHEAP_CONDEST checks the diagonal of a triangular matrix
% Copyright 2011-2012, Timothy A. Davis, http://www.suitesparse.com
if (isempty (d))
dmin = 1 ;
dmax = 1 ;
else
d = abs (d) ;
dmin = min (d) ;
dmax = max (d) ;
end
if (dmin == 0)
if (fail_if_singular)
error ('MATLAB:singularMatrix', ...
'Matrix is singular to working precision.');
else
warning ('MATLAB:singularMatrix', ...
'Matrix is singular to working precision.');
end
elseif (dmin < 2 * eps * (dmax))
% MATLAB treats this as a warning, but it is treated here as an error
% so that F=factorize(A) will abandon this factorization and use a
% better one, in its default strategy.
if (fail_if_singular)
error ('MATLAB:nearlySingularMatrix', ...
['Matrix is close to singular or badly scaled.\n' ...
' Results may be inaccurate. RCOND = %g'], dmin / dmax) ;
else
warning ('MATLAB:nearlySingularMatrix', ...
['Matrix is close to singular or badly scaled.\n' ...
' Results may be inaccurate. RCOND = %g'], dmin / dmax) ;
end
end
if (dmin == 0)
c = inf ;
else
c = dmax / dmin ;
end
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