Execute tasks with data dependencies

[rouson]

• The initialization reads the subprogram names
• The scheduler image assigns tasks to the compute images in an order defined by a DAG.
  • The scheduler image must record which compute image is doing each task.
  • The scheduler image must tell each compute image where to find any data the compute image needs.
• Each compute image does a task and places the task result in an outbox for pick-up.
  • Each outbox will be a buffer that can grow in size at runtime.
  • Because the buffer is used for communication, it must be a coarray.
  • Because the buffer will be a different size on each image at any given time, the outbox must be a derived type coarray with an allocatable component buffer.
• The compute images notify the scheduler image when they are ready for a new task

Tests

1. Check that the scheduler image received the ready-for-new-task notifications from each compute image that was assigned a task.
2. Is there a way to check whether the ordering specified by the DAG was satisfied?