add multiprocessing argument to run_blockwise convenience function.

if set to `False`, all blocks are run sequentially without any of the `Server`/`Client`/`Worker` interactions that can make debugging difficult

daisy/convenience.py

@@ -1,16 +1,23 @@
 from .cl_monitor import CLMonitor
 from .server import Server
+from .serial_server import SerialServer
 from .tcp import IOLooper
 from multiprocessing.pool import ThreadPool
 from multiprocessing import Event
 
 
-def run_blockwise(tasks):
+def run_blockwise(tasks, multiprocessing=True):
     """Schedule and run the given tasks.
 
     Args:
         list_of_tasks:
             The tasks to schedule over.
+        multiprocessing (bool):
+            If `False`, all multiprocessing is avoided and blocks are processed
+            sequentially. This is useful for debugging. This will only work for
+            tasks with a `process_function` that takes a single block as input
+            since a worker process would not be able to start a client and hook
+            up to the server.
 
     Return:
         bool:
@@ -27,16 +34,23 @@ def run_blockwise(tasks):
         tasks.extend(task.upstream_tasks)
 
     tasks = all_tasks
-    stop_event = Event()
-
-    IOLooper.clear()
-    with ThreadPool(processes=1) as pool:
-        result = pool.apply_async(_run_blockwise, args=(tasks, stop_event))
-        try:
-            return result.get()
-        except KeyboardInterrupt:
-            stop_event.set()
-            return result.get()
+
+    if not multiprocessing:
+        server = SerialServer()
+        cl_monitor = CLMonitor(server)
+        return server.run_blockwise(tasks)
+
+    else:
+        stop_event = Event()
+
+        IOLooper.clear()
+        with ThreadPool(processes=1) as pool:
+            result = pool.apply_async(_run_blockwise, args=(tasks, stop_event))
+            try:
+                return result.get()
+            except KeyboardInterrupt:
+                stop_event.set()
+                return result.get()
 
 
 def _run_blockwise(tasks, stop_event):