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function test18
%TEST18 test iterative refinement after backslash
%
% Example:
% test18
% See also: testall
% Copyright 2006-2012, Timothy A. Davis, http://www.suitesparse.com
index = ssget ;
[ignore f] = sort (max (index.nrows, index.ncols)) ;
f = f (1:100) ;
clf
% f = f(1)
for i = f
Prob = ssget (i) ;
disp (Prob) ;
A = Prob.A ;
[m n] = size (A) ;
if (~isreal (A) | m ~= n) %#ok
continue
end
b = rand (n,1) ;
x = A\b ;
r = b - A*x ;
x = x + A\r ;
fprintf ('\n%6.2e to %6.2e\n', norm (r), norm (b-A*x)) ;
end
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