build_BB.m

% MIT License
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% Copyright (c) 2017 Jose Bravo Ferreira
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% furnished to do so, subject to the following conditions:
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function [BB_col] = build_BB(n,BLKSZ)
    BB_col = cell(1,BLKSZ);
    d = BLKSZ*n+1;
    for j=1:BLKSZ
        BB = spalloc(n,d^2,2*n);
        for iii=1:n
            temp = zeros(d); temp(iii+(j-1)*n,d) = 1/2; temp(d,iii+(j-1)*n) = 1/2;
            BB(iii,:) = temp(:)';
        end
        BB_col{j} = BB;
    end
end