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function s = gb_issymmetric (G, option, herm)
%GB_ISSYMMETRIC check if symmetric or Hermitian
% Implements issymmetric (G,option) and ishermitian (G,option).
% SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
% SPDX-License-Identifier: Apache-2.0
% FUTURE: this can be much faster; see spsym in CHOLMOD.
[m, n, type] = gbsize (G) ;
if (m ~= n)
s = false ;
else
if (isequal (type, 'logical'))
G = gbnew (G, 'double') ;
end
if (herm && gb_contains (type, 'complex'))
% T = G', complex conjugate transpose
desc.in0 = 'transpose' ;
T = gbapply ('conj', G, desc) ;
else
% T = G.', array transpose
T = gbtrans (G) ;
end
switch (option)
case { 'skew' }
% G is skew symmetric/Hermitian if G+T is zero
s = (gbnorm (gb_eadd (G, '+', T), 1) == 0) ;
case { 'nonskew' }
% G is symmetric/Hermitian if G-T is zero
s = (gbnormdiff (G, T, 1) == 0) ;
otherwise
error ('GrB:error', 'invalid option') ;
end
clear T
if (s)
% also check the pattern; G might have explicit zeros
S = gb_spones (G, 'logical') ;
s = gbisequal (S, gbtrans (S)) ;
end
end
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