def runWorker(comm, histogramSize, gatherInterval, numEventsScaleFactor):
"""worker shared memory example for reducing a histogram to a viewer
Maintains a histogram. Continues to update the communicator and reduce until
no more workers participate in the communicator.
Assumes Each reduce is a histogram over only the previous worker events since
the last reduce.
ARGS:
comm - initial communicator to use
histogramSize - size of historgram to reduce
finalReducedHistFilename - filename for numpy .npy file for final histogram
"""
sharedMemDs = MockDataSource(numEventsScaleFactor)
localHistogram = np.zeros(histogramSize, np.int64)
idx = None
for idx, evt in enumerate(sharedMemDs.events()):
localHistogram[idx % histogramSize] += 1
if (idx % gatherInterval) == 0:
comm = collectiveCommUpdate(comm, stayInComm=True)
workerReduce(comm, localHistogram)
localHistogram[:] = 0
# check for last reduce
if (idx is not None) and (idx % gatherInterval) != 0:
comm = collectiveCommUpdate(comm, stayInComm=True)
workerReduce(comm, localHistogram)
# remove self from collective communication
dprint("before final comm update to remove self")
collectiveCommUpdate(comm, stayInComm=False)
dprint("after final comm update")
def runViewerReduceHistorgram(comm, histogramSize, finalReducedHistFilename):
"""Viewer shared memory example for reducing a histogram from worker ranks.
Maintains a histogram. Continues to update the communicator and reduce until
no more workers participate in the communicator.
Assumes Each reduce is a histogram over only the previous worker events since
the last reduce.
ARGS:
comm - initial communicator to use
histogramSize - size of historgram to reduce
finalReducedHistFilename - filename for numpy .npy file for final histogram
"""
assert comm.Get_rank() == 0
histogram = np.zeros(histogramSize, np.int64)
while True:
comm = collectiveCommUpdate(comm, stayInComm=True)
# check if only the viewer is left in communicator and exit if so
if comm.Get_size() == 1:
break
localHistogram = np.zeros(histogramSize, np.int64)
recvHistogram = np.zeros(histogramSize, np.int64)
dprint("before Reduce")
comm.Reduce(sendbuf=[localHistogram, MPI.INT64_T], recvbuf=[recvHistogram, MPI.INT64_T], op=MPI.SUM, root=0)
histogram[:] += recvHistogram[:]
print "rank=0 After Reduce. reduced histogram: %s" % histogram
np.save(file(finalReducedHistFilename, "w"), histogram)
print "rank=0 saved final reduced historgram=%s in file: %s" % (histogram, finalReducedHistFilename)
def collectiveCommUpdate(comm, stayInComm):
'''collectively update a communicator based on which ranks continue.
Note: requires rank 0 to be the root/viewer/master.
Rank 0 must always pass stayInComm=True
ARGS:
comm - MPI communicator
stayInComm - Bool - true if this rank will stay in the communicator
RETURN:
comm - a potentially new communicator based on ranks that stayed in,
however will be existing comm if no change.
comm will always have at least one rank in it (rank 0)
Example:
comm = collectiveCommUpdate(comm, True)
'''
dprint("collectiveCommUpdate start: before gathering stayInComm at root. Sending %r" % stayInComm)
if comm.Get_rank()==0:
assert stayInComm == True # root always stays in comm
recvObject = comm.gather(sendobj=True, root=0)
else:
comm.gather(sendobj=stayInComm, root=0)
dprint(" after gather. Before bcast to inform all in old communicatior of ranks to drop")
if comm.Get_rank()==0:
droppedRanks = [idx for idx, hasData in enumerate(recvObject) if not hasData]
comm.bcast(obj=droppedRanks, root=0)
else:
droppedRanks = comm.bcast()
dprint(" after bcast. droppedRanks=%r" % droppedRanks)
if len(droppedRanks)==0:
return comm
assert 0 not in droppedRanks
group = comm.Get_group()
newGroup = group.Excl(droppedRanks)
dprint(" before comm.Create(newGroup) where newGroup excludes ranks %s" % droppedRanks)
newComm = comm.Create(newGroup)
dprint(" after comm.Create(newGroup)")
return newComm
def workerReduce(comm, localHistogram):
dprint("before Reduce sending=%s" % localHistogram)
comm.Reduce(sendbuf=[localHistogram, MPI.INT64_T], recvbuf=[None, MPI.INT64_T], op=MPI.SUM, root=0)
dprint("after reduce")
def __init__(self, numEventsScaleFactor=1):
self.remainingEvents = max(0, numEventsScaleFactor * (MPI.COMM_WORLD.Get_rank() - 1))
dprint("MockDataSource with %d events" % self.remainingEvents)