Defined in File operator_node.h
This struct is a nested type of Class OperatorNodeBase.
struct to specify the callback function pointers for various operator events.
This exists mainly for optimization: if a callback is not needed, related surronding code would not be inserted into execution queue.
called when memory status changed
Memory status is defined by all layouts and addresses of DEV_VALUE deps and outputs; if any of it changes, this callback would be called before execution