Hi,
example 11.19 in this version of red book places a imageLoad in a while loop, keep polling until at least one fragment of the previous primitive has updated this value. However, GL spec 4.3 says "having one invocation poll memory written by another invocation assumes that the other invocation has been launched and can complete its writes". So how can we assure that fragment invocations of the previous primitive have been launched and completed its writes?