function R = gqr (A)
[m n] = size (A) ;

parent = cs_etree (sparse (A), 'col') ;

for i = 2:m
    i
    for k = 1:min(i-1,n)
    k
	% Givens rotation to zero out A(i,k) using A(k,k)
	G = cs_givens (A(k,k), A(i,k)) ;
	A ([k i],k:n) = G * A ([k i],k:n) ;
	A (i,k) = 0 ;
	% fprintf ('A(21,25)=%g\n', A(21,25)) ;
	% if (A(21,25) ~= 0)
	    % pause
	% end
    end
end
R = A ;
