11. Callbacks

Callbacks provide a generic way to store the information required to invoke a communication target, such as a chare's entry method, at a future time. Callbacks are often encountered when writing library code, where they provide a simple way to transfer control back to a client after the library has finished. For example, after finishing a reduction, you may want the results passed to some chare's entry method. To do this, you would create an object of type CkCallback with the chare's CkChareID and entry method index, and pass this callback object to the reduction library.