function [ok] = blkbidiag_symm_mul_ok()
ok = true;
% -------------------------------------------------------------
% You can change these parameters
m    = 2;
n    = 3;
N    = 4;
% -------------------------------------------------------------
% Define the problem
rand('seed', 123);

rand('seed', 123);

Hdia  = rand(n, n, N);
Hlow  = rand(n, n, N);
Ddia  = zeros(n, n, N); 

for k = 1:N
    dk = rand(n, n);
    Ddia(:,:,k)  = dk'*dk;
end

Hfull = ckbs_blkbidiag_mul(Hdia, Hlow, eye(n*N));
Dfull = ckbs_blkdiag_mul(Ddia, eye(n*N));

HDHfull = Hfull * Dfull *  Hfull';

[r, s]  = ckbs_blkbidiag_symm_mul(Hdia, Hlow, Ddia);

HDH     = ckbs_blktridiag_mul(r, s, eye(n*N));

check = HDH - HDHfull;

ok    = ok & ( max(max(abs(check))) < 1e-10 );
return
end