Class Task

caffe2/python/task.py:439–644

A Task is composed of an execution step and zero or more outputs. Tasks are executed in the context of a TaskGroup, which, in turn, can be run by a Session. Task outputs are fetched by the session at the end of the run. The recommended way of creating a task is by using `net_b

class Task(context.Managed):
    """
    A Task is composed of an execution step and zero or more outputs.
    Tasks are executed in the context of a TaskGroup, which, in turn, can
    be run by a Session.

    Task outputs are fetched by the session at the end of the run.

    The recommended way of creating a task is by using `net_builder.ops`.
    Example:

        from net_builder import ops
        with Node('trainer'), Task(name='my_task', num_instances=2):
            with ops.task_init():
                globl = ops.Const(0)
            with ops.task_instance_init():
                local = ops.Const(0)
            with ops.loop(100):
                ops.Copy(globl, local)
            with ops.task_instance_exit():
                ops.Add([globl, local], [globl])
            with ops.task_exit():
                ops.Mul([globl, globl], [globl])

    The task above will create 2 instances that will run in parallel.
    Each instance will copy `local` to `globl` 100 times, Then Add `local`
    to `globl` once. The `Mul` will only execute once, after all the instances
    of the task have finished.
    """

    # TASK_SETUP runs once per task, before/after all
    # concurrent task instances start/finish.
    TASK_SETUP = 'task_setup'
    # Setup will run once for each instance of the task.
    TASK_INSTANCE_SETUP = 'task_instance_setup'
    REPORT_STEP = 'report_step'
    _global_names_used = set()

    @staticmethod
    def _get_next_name(node, group, name):
        basename = str(node) + '/' + str(name)
        names_used = (
            Task._global_names_used
            if group is None else
            set(t.name for t in group._tasks_to_add))
        cur_name = basename
        i = 0
        while cur_name in names_used:
            i += 1
            cur_name = '%s:%d' % (basename, i)
        return cur_name

    def __init__(
            self, step=None, outputs=None,
            workspace_type=None, group=None, node=None, name=None,
            num_instances=None):
        """
        Instantiate a Task and add it to the current TaskGroup and Node.