n = 500;
r = 3;
B = randn(n,r+1);
S = spdiags(B,0:r,n,n);S = S+S';
x = sdpvar(n,1);
X = diag(x)-S;
p = randperm(n);
X = X(p,p);
F = X >= 0
spy(F)
+++++++++++++++++++++++++++++++++++++++++++++++++++++
|   ID|      Constraint|                        Type|
+++++++++++++++++++++++++++++++++++++++++++++++++++++
|   #1|   Numeric value|   Matrix inequality 500x500|
+++++++++++++++++++++++++++++++++++++++++++++++++++++