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function result = get_symmetry (A,quick)
%GET_SYMMETRY: does the same thing as the spsym mexFunction.
% It's just a lot slower and uses much more memory. This function
% is meant for testing and documentation only.
[m n] = size (A) ;
if (m ~= n)
result = 1 ; % rectangular
return
end
if (nargin < 2)
quick = 0 ;
end
d = diag (A) ;
posdiag = all (real (d) > 0) & all (imag (d) == 0) ;
if (quick & ~posdiag)
result = 2 ; % Not a candidate for sparse Cholesky.
elseif (~isreal (A) & nnz (A-A') == 0)
if (posdiag)
result = 7 ; % complex Hermitian, with positive diagonal
else
result = 4 ; % complex Hermitian, nonpositive diagonal
end
elseif (nnz (A-A.') == 0)
if (posdiag)
result = 6 ; % symmetric with positive diagonal
else
result = 3 ; % symmetric, nonpositive diagonal
end
elseif (nnz (A+A.') == 0)
result = 5 ; % skew symmetric
else
result = 2 ; % unsymmetric
end
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