What are priorities?
Priorities are special values that can be associated with messages, so that the Charm++ scheduler will prefer higher priority messages when choosing a message to deliver. Priorities are respected by Charm++ as much as possible: until there are higher priority messages in the queue, lower priority message will never be delivered. Nevertheless, this is not a guarantee, and a lower priority message can be delivered before a higher priority one. Messages with priorities are typically used to perform optimizations on the order of the computation. For integer priorities, the smaller the priority value, the higher the priority of the message. Negative value are therefore higher priority than positive ones. To enable and set a message’s priority there is a special new syntax and CkPriorityPtr function; see the manual for details. If no priority is set, messages have a default priority of zero.
