worker: split build stage from prepare

artiq/language/experiment.py

@@ -1,6 +1,6 @@
 from inspect import isclass
 
-__all__ = ["Experiment", "has_analyze", "is_experiment"]
+__all__ = ["Experiment", "is_experiment"]
 
 
 class Experiment:
@@ -9,11 +9,28 @@ class Experiment:
     Deriving from this class enables automatic experiment discovery in
     Python modules.
     """
+    def prepare(self):
+        """Entry point for pre-computing data necessary for running the
+        experiment.
+
+        Doing such computations outside of ``run`` enables more efficient
+        scheduling of multiple experiments that need to access the shared
+        hardware during part of their execution.
+
+        This method must not interact with the hardware.
+        """
+        pass
+
     def run(self):
         """The main entry point of the experiment.
 
         This method must be overloaded by the user to implement the main
         control flow of the experiment.
+
+        This method may interact with the hardware.
+
+        The experiment may call the scheduler's ``pause`` method while in
+        ``run``.
         """
         raise NotImplementedError
 
@@ -32,11 +49,6 @@ class Experiment:
         pass
 
 
-def has_analyze(experiment):
-    """Checks if an experiment instance overloaded its ``analyze`` method."""
-    return experiment.analyze.__func__ is not Experiment.analyze
-
-
 def is_experiment(o):
     """Checks if a Python object is an instantiable experiment."""
     return isclass(o) and issubclass(o, Experiment) and o is not Experiment

artiq/master/scheduler.py

@@ -99,13 +99,14 @@ class Run:
         yield from self.worker.close()
         del self._notifier[self.rid]
 
-    _prepare = _mk_worker_method("prepare")
+    _build = _mk_worker_method("build")
 
     @asyncio.coroutine
-    def prepare(self):
-        yield from self._prepare(self.rid, self.pipeline_name, self.expid,
+    def build(self):
+        yield from self._build(self.rid, self.pipeline_name, self.expid,
                                self.priority)
 
+    prepare = _mk_worker_method("prepare")
     run = _mk_worker_method("run")
     resume = _mk_worker_method("resume")
     analyze = _mk_worker_method("analyze")
@@ -188,6 +189,7 @@ class PrepareStage(TaskObject):
                 run.status = RunStatus.preparing
                 self.flush_tracker.add(run.rid)
                 try:
+                    yield from run.build()
                     yield from run.prepare()
                 except:
                     logger.warning("got worker exception in prepare stage, "

artiq/master/worker.py

@@ -28,11 +28,11 @@ class WorkerError(Exception):
 class Worker:
     def __init__(self, handlers,
                  send_timeout=0.5, term_timeout=1.0,
-                 prepare_timeout=15.0, results_timeout=15.0):
+                 build_timeout=15.0, results_timeout=15.0):
         self.handlers = handlers
         self.send_timeout = send_timeout
         self.term_timeout = term_timeout
-        self.prepare_timeout = prepare_timeout
+        self.build_timeout = build_timeout
         self.results_timeout = results_timeout
 
         self.rid = None
@@ -142,7 +142,7 @@ class Worker:
             [self.process.stdout.readline(), self.closed.wait()],
             timeout=timeout, return_when=asyncio.FIRST_COMPLETED)
         if all(f.cancelled() for f in fs):
-            raise WorkerTimeout("Timeout sending data to worker")
+            raise WorkerTimeout("Timeout receiving data from worker")
         if self.closed.is_set():
             raise WorkerError("Data transmission to worker cancelled")
         line = fs[0].result()
@@ -209,16 +209,20 @@ class Worker:
         return completed
 
     @asyncio.coroutine
-    def prepare(self, rid, pipeline_name, expid, priority):
+    def build(self, rid, pipeline_name, expid, priority):
         self.rid = rid
         yield from self._create_process()
         yield from self._worker_action(
-            {"action": "prepare",
+            {"action": "build",
              "rid": rid,
              "pipeline_name": pipeline_name,
              "expid": expid,
              "priority": priority},
-            self.prepare_timeout)
+            self.build_timeout)
+
+    @asyncio.coroutine
+    def prepare(self):
+        yield from self._worker_action({"action": "prepare"})
 
     @asyncio.coroutine
     def run(self):

artiq/master/worker_impl.py

@@ -117,7 +117,7 @@ def main():
         while True:
             obj = get_object()
             action = obj["action"]
-            if action == "prepare":
+            if action == "build":
                 start_time = time.localtime()
                 rid = obj["rid"]
                 pipeline_name = obj["pipeline_name"]
@@ -131,6 +131,9 @@ def main():
                                **expid["arguments"])
                 rdb.build()
                 put_object({"action": "completed"})
+            elif action == "prepare":
+                exp_inst.prepare()
+                put_object({"action": "completed"})
             elif action == "run":
                 exp_inst.run()
                 put_object({"action": "completed"})

artiq/test/worker.py

@@ -32,7 +32,8 @@ class WatchdogTimeoutInBuild(Experiment, AutoDB):
 @asyncio.coroutine
 def _call_worker(worker, expid):
     try:
-        yield from worker.prepare(0, "main", expid, 0)
+        yield from worker.build(0, "main", expid, 0)
+        yield from worker.prepare()
         yield from worker.run()
         yield from worker.analyze()
     finally: