Issue #12708: Add starmap() and starmap_async() methods (similar to itertools.starmap()) to multiprocessing.Pool.
Patch by Hynek Schlawack.
diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index f42d353..5cae4c1 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -1066,11 +1066,12 @@
PoolProxy = MakeProxyType('PoolProxy', (
'apply', 'apply_async', 'close', 'imap', 'imap_unordered', 'join',
- 'map', 'map_async', 'terminate'
+ 'map', 'map_async', 'starmap', 'starmap_async', 'terminate'
))
PoolProxy._method_to_typeid_ = {
'apply_async': 'AsyncResult',
'map_async': 'AsyncResult',
+ 'starmap_async': 'AsyncResult',
'imap': 'Iterator',
'imap_unordered': 'Iterator'
}
diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index 0c29e64..7039d16 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -64,6 +64,9 @@
def mapstar(args):
return list(map(*args))
+def starmapstar(args):
+ return list(itertools.starmap(args[0], args[1]))
+
#
# Code run by worker processes
#
@@ -248,7 +251,25 @@
in a list that is returned.
'''
assert self._state == RUN
- return self.map_async(func, iterable, chunksize).get()
+ return self._map_async(func, iterable, mapstar, chunksize).get()
+
+ def starmap(self, func, iterable, chunksize=None):
+ '''
+ Like `map()` method but the elements of the `iterable` are expected to
+ be iterables as well and will be unpacked as arguments. Hence
+ `func` and (a, b) becomes func(a, b).
+ '''
+ assert self._state == RUN
+ return self._map_async(func, iterable, starmapstar, chunksize).get()
+
+ def starmap_async(self, func, iterable, chunksize=None, callback=None,
+ error_callback=None):
+ '''
+ Asynchronous version of `starmap()` method.
+ '''
+ assert self._state == RUN
+ return self._map_async(func, iterable, starmapstar, chunksize,
+ callback, error_callback)
def imap(self, func, iterable, chunksize=1):
'''
@@ -302,6 +323,13 @@
Asynchronous version of `map()` method.
'''
assert self._state == RUN
+ return self._map_async(func, iterable, mapstar, chunksize)
+
+ def _map_async(self, func, iterable, mapper, chunksize=None, callback=None,
+ error_callback=None):
+ '''
+ Helper function to implement map, starmap and their async counterparts.
+ '''
if not hasattr(iterable, '__len__'):
iterable = list(iterable)
@@ -315,7 +343,7 @@
task_batches = Pool._get_tasks(func, iterable, chunksize)
result = MapResult(self._cache, chunksize, len(iterable), callback,
error_callback=error_callback)
- self._taskqueue.put((((result._job, i, mapstar, (x,), {})
+ self._taskqueue.put((((result._job, i, mapper, (x,), {})
for i, x in enumerate(task_batches)), None))
return result
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index b99201b..93cc11d 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -8,6 +8,7 @@
import queue as pyqueue
import time
import io
+import itertools
import sys
import os
import gc
@@ -1125,6 +1126,9 @@
time.sleep(wait)
return x*x
+def mul(x, y):
+ return x*y
+
class _TestPool(BaseTestCase):
def test_apply(self):
@@ -1138,6 +1142,20 @@
self.assertEqual(pmap(sqr, list(range(100)), chunksize=20),
list(map(sqr, list(range(100)))))
+ def test_starmap(self):
+ psmap = self.pool.starmap
+ tuples = list(zip(range(10), range(9,-1, -1)))
+ self.assertEqual(psmap(mul, tuples),
+ list(itertools.starmap(mul, tuples)))
+ tuples = list(zip(range(100), range(99,-1, -1)))
+ self.assertEqual(psmap(mul, tuples, chunksize=20),
+ list(itertools.starmap(mul, tuples)))
+
+ def test_starmap_async(self):
+ tuples = list(zip(range(100), range(99,-1, -1)))
+ self.assertEqual(self.pool.starmap_async(mul, tuples).get(),
+ list(itertools.starmap(mul, tuples)))
+
def test_map_chunksize(self):
try:
self.pool.map_async(sqr, [], chunksize=1).get(timeout=TIMEOUT1)