Why should I prefer the callback way to return data rather than using [sync] entry methods?
There are a few reasons for that: • The caller needs to be threaded, which implies some overhead in creating the thread. Moreover the threaded entry method will suspend waiting for the data, preventing any code after the remote method invocation to proceed in parallel. • Threaded entry methods are still methods of an object. While they are suspended other entry methods for the same object (or even the same threaded entry method) can be called. This allows for potential problems if the suspending method does leave some objects in an inconsistent state. • Finally, and probably most important, [sync] entry methods can only be used to return a value that can be computed by a single chare. When more flexibility is needed, such in cases where the resulting value needs to the contribution of multiple objects, the callback methodology is the only one available. The caller could for example send a broadcast to a chare array, which will use a reduction to collect back the results after they have
