imported>T1t0: Created page with "= Simple multi-process hello world = * helloworld.py:

 #!/usr/bin/env python  # chmod +x hellompi.py # mpiexec -n 10 hellompi.py  from mpi4py import MPI  size = MPI.COM..."

2014-12-24T02:16:05Z

Created page with "= Simple multi-process hello world = * helloworld.py: <pre> #!/usr/bin/env python # chmod +x hellompi.py # mpiexec -n 10 hellompi.py from mpi4py import MPI size = MPI.COM..."

New page

= Simple multi-process hello world =

* helloworld.py:

<pre>
#!/usr/bin/env python

# chmod +x hellompi.py
# mpiexec -n 10 hellompi.py

from mpi4py import MPI

size = MPI.COMM_WORLD.Get_size()
rank = MPI.COMM_WORLD.Get_rank()
name = MPI.Get_processor_name()

print "Hello from process " + str(rank + 1) + " of " + str(size) + " on " + str(name)
</pre>

run with <pre>mpiexec -n 10 hellompi.py</pre>

= Better spawned and reduced sum example =

* master.py:

<pre>
#!/usr/bin/env python

from mpi4py import MPI
from array import array

def run(debug = False):
worker = MPI.COMM_SELF.Spawn("worker.py", None, 3)

data_size = 1000000

try:
data = array('i')
for i in range(0, data_size):
data.append(1)

print "Broadcasting input data len: ", len(data), " content: ", data[0]
worker.Bcast([data, MPI.INT], root = MPI.ROOT)

result = array('i', [0])
worker.Reduce(sendbuf = None, recvbuf = [result, MPI.INT], op = MPI.SUM, root = MPI.ROOT)
result = result[0] # strange thing (Reduce logic)

print "Calculated value of sum is", result

except Exception as ex:
print "Unexpected error:"
print ex

worker.Disconnect()

def __main__():
run()

__main__()
</pre>

* worker.py:

<pre>
#!/usr/bin/env python

from mpi4py import MPI
from array import array

def run(debug = False):
master = MPI.Comm.Get_parent()
my_rank = master.Get_rank()
n_procs = master.Get_size()

data_size = 10241024

try:
data = array('i')
for i in range(0, data_size):
data.append(0)

master.Bcast([data, MPI.INT], root = 0)
#print "# Broadcast finished and data on rank ", my_rank, " is len ", len(data), " data: ", data

work_size = int(data_size / n_procs)

work_start = my_rank * work_size
work_limit = int(0)

# if is the last proc, work_limit is the end of data
if my_rank == (n_procs - 1):
work_limit = data_size
else:
work_limit = work_start + work_size

result = int(0)

for i in range(work_start, work_limit):
result += data[i]

print "my_rank: ", my_rank, " work_start: ", work_start, " work_limit: ", work_limit, "result = ", result

result = array('i', [result]) # strange thing (Reduce logic)
master.Reduce(sendbuf = [result, MPI.INT], recvbuf = None, op = MPI.SUM, root = 0)

except Exception as ex:
print "# Unexpected error:"
print ex

#print "# Disconnecting from rank %d" % my_rank
master.Disconnect()

def __main__():
run()

__main__()
</pre>

run the code with <pre>python master.py</pre>

= Depends =

<pre>apt-get install libopenmpi-dev python-mpi4py</pre>

= References =

* http://mpi4py.readthedocs.org/en/latest/tutorial.html#dynamic-process-management
* https://portal.tacc.utexas.edu/c/document_library/get_file?uuid=be16db01-57d9-4422-b5d5-17625445f351&groupId=13601

[[Category:develop]]
[[Category:python]]

Mpi4py - Revision history

imported>T1t0: Created page with "= Simple multi-process hello world = * helloworld.py:
#!/usr/bin/env python # chmod +x hellompi.py # mpiexec -n 10 hellompi.py from mpi4py import MPI size = MPI.COM..."