Using irecv and isend

[Ao Liu]

Hi, How may I do the following?

I want rank 0 to wait for rank 1 to finish calculation of b, and receive b;

while this waiting, it should proceed and do something else.

I wrote the following, but it didn't work, a was only a memory address.

if commrank == 0:

a = comm.irecv()

print 'ahei'

        print a

else:

time.sleep(1)

b = 1

request = comm.isend(b,dest=0)

print 'aha'

Thanks,

Ao

[Lisandro Dalcin]

I recommend you to read some MPI tutorial about non-blocking communication

[dalcinl@macarena mpi4py-dev]$ cat ~/tmp/mpi_wait.py
from mpi4py import MPI
comm = MPI.COMM_WORLD
import time

assert comm.size == 2
if comm.rank == 0:
request = comm.irecv(source=1)
while not request.Get_status():
print("waiting")
time.sleep(0.1)
msg = request.wait()
print(msg)
else:
time.sleep(1)
comm.send('Hello, World!', dest=0)

[dalcinl@macarena mpi4py-dev]$ mpiexec -n 2 python ~/tmp/mpi_wait.py
waiting
waiting
waiting
waiting
waiting
waiting
waiting
waiting
waiting
waiting
Hello, World!



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[Ao Liu]

That is very nice of you.

I hope this can be implemented in the documentations of MPI4PY. I googled a lot but found nothing, then I had to bother the group.

Best,

Ao

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I am Ao.Liu, always hungry and still waiting for what I've always been believing.

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[Ao Liu]

I got this error when doing what you said.

Traceback (most recent call last):

  File "try.py", line 30, in <module>

    a = comm.irecv(source=1)

  File "Comm.pyx", line 850, in mpi4py.MPI.Comm.irecv (src/mpi4py.MPI.c:67545)

TypeError: irecv() got an unexpected keyword argument 'source'

[Ao Liu]

succeeded by 

comm.irecv(dest=1)

[Lisandro Dalcin]

On 31 October 2013 00:27, Ao Liu <frank...@gmail.com> wrote:
> succeeded by
> comm.irecv(dest=1)
>

Yes, that's a but in the API, I've fixed it in mpi4py-dev. To be safe
for a future upgrade, use comm.irecv(None, 1)

> https://groups.google.com/d/msgid/mpi4py/CA%2Buij29z_gQq0g5wamXYvKov4dym_Gpfno%2BS-dTbMp_Of3D9rg%40mail.gmail.com.

>
> For more options, visit https://groups.google.com/groups/opt_out.



--

[Lisandro Dalcin]

On 31 October 2013 00:14, Ao Liu <frank...@gmail.com> wrote:
> I hope this can be implemented in the documentations of MPI4PY. I googled a
> lot but found nothing, then I had to bother the group.

This is the hope of many uses. And my hope is that users contribute
back to the project with documentation and examples, e.g.
http://jeremybejarano.zzl.org/MPIwithPython/index.html

[Ao Liu]

How could users edit the page? If you could open it like Wiki did, and keep your approval authority, it would be nice that everyone can write their own cases, and wait for your approval.

Best,

Ao

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For more options, visit https://groups.google.com/groups/opt_out.

[Lisandro Dalcin]

On 31 October 2013 00:36, Ao Liu <frank...@gmail.com> wrote:
> How could users edit the page? If you could open it like Wiki did, and keep
> your approval authority, it would be nice that everyone can write their own
> cases, and wait for your approval.
>

Do you mean the bitbucket Wiki
https://bitbucket.org/mpi4py/mpi4py/wiki/Home? Bitbucket handle wikis
with repositories, you can clone, edit, commit, push ask for a pull
request.

[Lisandro Dalcin]

On 31 October 2013 12:28, Lisandro Dalcin <dal...@gmail.com> wrote:
> On 31 October 2013 00:36, Ao Liu <frank...@gmail.com> wrote:
>> How could users edit the page? If you could open it like Wiki did, and keep
>> your approval authority, it would be nice that everyone can write their own
>> cases, and wait for your approval.
>>
>
> Do you mean the bitbucket Wiki
> https://bitbucket.org/mpi4py/mpi4py/wiki/Home? Bitbucket handle wikis
> with repositories, you can clone, edit, commit, push ask for a pull
> request.
>

Moreover, mpi4py's wiki at Bitbucket DO IS public, however I guess you
need to register in Bitbucket to actually be able to make editions.