function test1( A, b, shift, M )
%        test1( A, b, shift, M );
% test1 uses minres.m to solve (A - shift*I)x = b.
% A  is assumed to be a dense or sparse matrix.
% M  must be positive definite (or []).
%
% Examples:
% n     = 10;
% [A,b] = diagA(n);  % generates A = sparse diag(1:n), b = ones(n,1);
%
% test1( A,b,0,[] )  % solves      Ax = b.
% test1( A,b,2,[] )  % solves (A-2I)x = b.
%
% M = A;
% for i=2:4,  M(i,i) = 1; end
% test1( A,b,0,M )   % solves      Ax = b with good preconditioner M.
% test1( A,b,2,M )   % solves (A-2I)x = b with good preconditioner M.

% 17 Oct 2003: First version for testing minres.
%  ------------------------------------------------------------------

true   = 1;
false  = 0;

[n,n]  = size(A);
[m,m]  = size(M);
iw     = [];
rw     = [];
precon = m==n;
show   = true;
check  = true;
itnlim = n*5;
rtol   = 1.0e-12;

[ x, istop, itn, rnorm, Arnorm, Anorm, Acond, ynorm ] = ...
  minres( n, b, A, M, iw, rw,  ...
          precon, shift, show, check, itnlim, rtol );

%  print the solution and some clue about whether it is ok.

disp(' '); disp( 'Solution:' )
for j = 1:n
   fprintf( '%22.14e', x(j) )
end
disp(' ')

%  End of test1.