## Matrix for long Y tree
print "long Y tree"
A=matrix(7,7,[
[0,1,0,1,0,1,0],
[1,1,1,0,0,0,0],
[0,1,1,0,0,0,0],
[1,0,0,1,1,0,0],
[0,0,0,1,1,0,0],
[1,0,0,0,0,1,1],
[0,0,0,0,0,1,1]])
print "A="
show(A)
print "rank=%s"%A.rank();
print "eigenvalues=%s"%A.eigenvalues();
print "Auxiliary SSP matrix for A:"
show(SSPmatrix(A).change_ring(ZZ));
print "has_SSP?",has_SSP(A);
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long Y tree
A=
rank=5
eigenvalues=[2, 2, 0, 0, -1.460504870018764?, 0.7608767217434455?,
2.699628148275318?]
Auxiliary SSP matrix for A:
has_SSP? True
long Y tree
A=
rank=5
eigenvalues=[2, 2, 0, 0, -1.460504870018764?, 0.7608767217434455?, 2.699628148275318?]
Auxiliary SSP matrix for A:
has_SSP? True
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