import multiprocessing
import os
import re
import sys
import time
from .processes import ForkedProcess
from .remoteproxy import ClosedError
class CanceledError(Exception):
"""Raised when the progress dialog is canceled during a processing operation."""
pass
class Parallelize(object):
"""
Class for ultra-simple inline parallelization on multi-core CPUs
Example::
## Here is the serial (single-process) task:
tasks = [1, 2, 4, 8]
results = []
for task in tasks:
result = processTask(task)
results.append(result)
print(results)
## Here is the parallelized version:
tasks = [1, 2, 4, 8]
results = []
with Parallelize(tasks, workers=4, results=results) as tasker:
for task in tasker:
result = processTask(task)
tasker.results.append(result)
print(results)
The only major caveat is that *result* in the example above must be picklable,
since it is automatically sent via pipe back to the parent process.
"""
def __init__(self, tasks=None, workers=None, block=True, progressDialog=None, randomReseed=True, **kwds):
"""
=============== ===================================================================
**Arguments:**
tasks list of objects to be processed (Parallelize will determine how to
distribute the tasks). If unspecified, then each worker will receive
a single task with a unique id number.
workers number of worker processes or None to use number of CPUs in the
system
progressDialog optional dict of arguments for ProgressDialog
to update while tasks are processed
randomReseed If True, each forked process will reseed its random number generator
to ensure independent results. Works with the built-in random
and numpy.random.
kwds objects to be shared by proxy with child processes (they will
appear as attributes of the tasker)
=============== ===================================================================
"""
## Generate progress dialog.
## Note that we want to avoid letting forked child processes play with progress dialogs..
self.showProgress = False
if progressDialog is not None:
self.showProgress = True
if isinstance(progressDialog, str):
progressDialog = {'labelText': progressDialog}
from ..widgets.ProgressDialog import ProgressDialog
self.progressDlg = ProgressDialog(**progressDialog)
if workers is None:
workers = self.suggestedWorkerCount()
if not hasattr(os, 'fork'):
workers = 1
self.workers = workers
if tasks is None:
tasks = range(workers)
self.tasks = list(tasks)
self.reseed = randomReseed
self.kwds = kwds.copy()
self.kwds['_taskStarted'] = self._taskStarted
def __enter__(self):
self.proc = None
if self.workers == 1:
return self.runSerial()
else:
return self.runParallel()
def __exit__(self, *exc_info):
if self.proc is not None: ## worker
exceptOccurred = exc_info[0] is not None ## hit an exception during processing.
try:
if exceptOccurred:
sys.excepthook(*exc_info)
finally:
#print os.getpid(), 'exit'
os._exit(1 if exceptOccurred else 0)
else: ## parent
if self.showProgress:
try:
self.progressDlg.__exit__(None, None, None)
except Exception:
pass
def runSerial(self):
if self.showProgress:
self.progressDlg.__enter__()
self.progressDlg.setMaximum(len(self.tasks))
self.progress = {os.getpid(): []}
return Tasker(self, None, self.tasks, self.kwds)
def runParallel(self):
self.childs = []
## break up tasks into one set per worker
workers = self.workers
chunks = [[] for i in range(workers)]
i = 0
for i in range(len(self.tasks)):
chunks[i%workers].append(self.tasks[i])
## fork and assign tasks to each worker
for i in range(workers):
proc = ForkedProcess(target=None, preProxy=self.kwds, randomReseed=self.reseed)
if not proc.isParent:
self.proc = proc
return Tasker(self, proc, chunks[i], proc.forkedProxies)
else:
self.childs.append(proc)
## Keep track of the progress of each worker independently.
self.progress = dict([(ch.childPid, []) for ch in self.childs])
## for each child process, self.progress[pid] is a list
## of task indexes. The last index is the task currently being
## processed; all others are finished.
try:
if self.showProgress:
self.progressDlg.__enter__()
self.progressDlg.setMaximum(len(self.tasks))
## process events from workers until all have exited.
activeChilds = self.childs[:]
self.exitCodes = []
pollInterval = 0.01
while len(activeChilds) > 0:
waitingChildren = 0
rem = []
for ch in activeChilds:
try:
n = ch.processRequests()
if n > 0:
waitingChildren += 1
except ClosedError:
#print ch.childPid, 'process finished'
rem.append(ch)
if self.showProgress:
self.progressDlg += 1
#print "remove:", [ch.childPid for ch in rem]
for ch in rem:
activeChilds.remove(ch)
while True:
try:
pid, exitcode = os.waitpid(ch.childPid, 0)
self.exitCodes.append(exitcode)
break
except OSError as ex:
if ex.errno == 4: ## If we get this error, just try again
continue
#print "Ignored system call interruption"
else:
raise
#print [ch.childPid for ch in activeChilds]
if self.showProgress and self.progressDlg.wasCanceled():
for ch in activeChilds:
ch.kill()
raise CanceledError()
## adjust polling interval--prefer to get exactly 1 event per poll cycle.
if waitingChildren > 1:
pollInterval *= 0.7
elif waitingChildren == 0:
pollInterval /= 0.7
pollInterval = max(min(pollInterval, 0.5), 0.0005) ## but keep it within reasonable limits
time.sleep(pollInterval)
finally:
if self.showProgress:
self.progressDlg.__exit__(None, None, None)
for ch in self.childs:
ch.join()
if len(self.exitCodes) < len(self.childs):
raise Exception("Parallelizer started %d processes but only received exit codes from %d." % (len(self.childs), len(self.exitCodes)))
for code in self.exitCodes:
if code != 0:
raise Exception("Error occurred in parallel-executed subprocess (console output may have more information).")
return [] ## no tasks for parent process.
@staticmethod
def suggestedWorkerCount():
if 'linux' in sys.platform:
## I think we can do a little better here..
## cpu_count does not consider that there is little extra benefit to using hyperthreaded cores.
try:
cores = {}
pid = None
with open('/proc/cpuinfo') as fd:
for line in fd:
m = re.match(r'physical id\s+:\s+(\d+)', line)
if m is not None:
pid = m.groups()[0]
m = re.match(r'cpu cores\s+:\s+(\d+)', line)
if m is not None:
cores[pid] = int(m.groups()[0])
return sum(cores.values())
except:
return multiprocessing.cpu_count()
else:
return multiprocessing.cpu_count()
def _taskStarted(self, pid, i, **kwds):
## called remotely by tasker to indicate it has started working on task i
#print pid, 'reported starting task', i
if self.showProgress:
if len(self.progress[pid]) > 0:
self.progressDlg += 1
if pid == os.getpid(): ## single-worker process
if self.progressDlg.wasCanceled():
raise CanceledError()
self.progress[pid].append(i)
class Tasker(object):
def __init__(self, parallelizer, process, tasks, kwds):
self.proc = process
self.par = parallelizer
self.tasks = tasks
for k, v in kwds.items():
setattr(self, k, v)
def __iter__(self):
## we could fix this up such that tasks are retrieved from the parent process one at a time..
for i, task in enumerate(self.tasks):
self.index = i
#print os.getpid(), 'starting task', i
self._taskStarted(os.getpid(), i, _callSync='off')
yield task
if self.proc is not None:
#print os.getpid(), 'no more tasks'
self.proc.close()
def process(self):
"""
Process requests from parent.
Usually it is not necessary to call this unless you would like to
receive messages (such as exit requests) during an iteration.
"""
if self.proc is not None:
self.proc.processRequests()
def numWorkers(self):
"""
Return the number of parallel workers
"""
return self.par.workers
#class Parallelizer:
#"""
#Use::
#p = Parallelizer()
#with p(4) as i:
#p.finish(do_work(i))
#print p.results()
#"""
#def __init__(self):
#pass
#def __call__(self, n):
#self.replies = []
#self.conn = None ## indicates this is the parent process
#return Session(self, n)
#def finish(self, data):
#if self.conn is None:
#self.replies.append((self.i, data))
#else:
##print "send", self.i, data
#self.conn.send((self.i, data))
#os._exit(0)
#def result(self):
#print self.replies
#class Session:
#def __init__(self, par, n):
#self.par = par
#self.n = n
#def __enter__(self):
#self.childs = []
#for i in range(1, self.n):
#c1, c2 = multiprocessing.Pipe()
#pid = os.fork()
#if pid == 0: ## child
#self.par.i = i
#self.par.conn = c2
#self.childs = None
#c1.close()
#return i
#else:
#self.childs.append(c1)
#c2.close()
#self.par.i = 0
#return 0
#def __exit__(self, *exc_info):
#if exc_info[0] is not None:
#sys.excepthook(*exc_info)
#if self.childs is not None:
#self.par.replies.extend([conn.recv() for conn in self.childs])
#else:
#self.par.finish(None)