- bug fix in killed process detection

parfor/__init__.py

@@ -7,6 +7,7 @@ from pickle import PicklingError, dispatch_table
 from psutil import Process
 from collections import OrderedDict
 from io import BytesIO
+from warnings import warn
 
 try:
     from javabridge import kill_vm
@@ -423,6 +424,7 @@ class parpool(object):
             ctx = multiprocessing.get_context('spawn')
         else:
             ctx = multiprocessing
+        self.is_started = False
         self.n_tasks = ctx.Value('i', self.nP)
         self.event = ctx.Event()
         self.queue_in = ctx.Queue(qsize or 3 * self.nP)
@@ -453,6 +455,7 @@ class parpool(object):
             for handle, task in self.tasks.items():  # retry a task if the process doing it was killed
                 if task.pid is not None and task.pid not in [child.pid for child in Process().children()]:
                     self.queue_in.put(task)
+                    warn('Task {} was restarted because process {} was probably killed.'.format(task.handle, task.pid))
             return False
 
     def error(self, error):
@@ -460,23 +463,27 @@ class parpool(object):
         raise Exception('Error occured in worker: {}'.format(error))
 
     def task_error(self, handle, error):
-        task = self.tasks[handle]
+        if handle in self:
-        print('Error from process working on iteration {}:\n'.format(handle))
+            task = self.tasks[handle]
-        print(error)
+            print('Error from process working on iteration {}:\n'.format(handle))
-        self.close()
+            print(error)
-        print('Retrying in main thread...')
+            self.close()
-        fun = task.fun.__name__
+            print('Retrying in main thread...')
-        task()
+            fun = task.fun.__name__
-        raise Exception('Function \'{}\' cannot be executed by parfor, amend or execute in serial.'.format(fun))
+            task()
+            raise Exception('Function \'{}\' cannot be executed by parfor, amend or execute in serial.'.format(fun))
 
     def done(self, task):
-        self.tasks[task.handle] = task
+        if task.handle in self:  # if not, the task was restarted erroneously
-        if self.bar is not None:
+            self.tasks[task.handle] = task
-            self.bar.update(self.bar_lengths.pop(task.handle))
+            if self.bar is not None:
-        self._qbar_update()
+                self.bar.update(self.bar_lengths.pop(task.handle))
+            self._qbar_update()
 
     def started(self, handle, pid):
-        self.tasks[handle].pid = pid
+        self.is_started = True
+        if handle in self:  # if not, the task was restarted erroneously
+            self.tasks[handle].pid = pid
 
     def __call__(self, n, fun=None, args=None, kwargs=None, handle=None, barlength=1):
         """ Add new iteration, using optional manually defined handle."""
@@ -514,11 +521,13 @@ class parpool(object):
         if handle not in self:
             raise ValueError('No handle: {}'.format(handle))
         while not self.tasks[handle].done:
-            if not self._get_from_queue() and not self.tasks[handle].done and not self.working:
+            if not self._get_from_queue() and not self.tasks[handle].done and self.is_started and not self.working:
                 for _ in range(10):  # wait some time while processing possible new messages
                     self._get_from_queue()
-                if not self._get_from_queue() and not self.tasks[handle].done and not self.working:
+                if not self._get_from_queue() and not self.tasks[handle].done and self.is_started and not self.working:
+                    # retry a task if the process was killed while retrieving the task
                     self.queue_in.put(self.tasks[handle])
+                    warn('Task {} was restarted because the process retrieving it was probably killed.'.format(handle))
         result = self.tasks[handle].result
         self.tasks.pop(handle)
         return result
@@ -607,8 +616,8 @@ class parpool(object):
                 try:
                     task = self.queue_in.get(True, 0.02)
                     try:
-                        task.set_from_cache(self.cache)
                         self.add_to_queue('started', task.handle, pid)
+                        task.set_from_cache(self.cache)
                         self.add_to_queue('done', task())
                     except Exception:
                         self.add_to_queue('task_error', task.handle, format_exc())

setup.py

@@ -5,7 +5,7 @@ with open("README.md", "r") as fh:
 
 setuptools.setup(
     name="parfor",
-    version="2022.3.0",
+    version="2022.3.1",
     author="Wim Pomp",
     author_email="wimpomp@gmail.com",
     description="A package to mimic the use of parfor as done in Matlab.",