CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Implementation of MPI

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 6, 2008, 15:23
Default Implementation of MPI
  #1
Ertan Karaismail
Guest
 
Posts: n/a
Hi all, I am working on a 3D FVM based CFD code. It is runnning on a staggered grid, and I need to parallelize this code. I have some experience with PVM, but this time I have to use MPI. With PVM, we used to use a master code to spawn slaves and then each slave was running the same code with different grid info. To be more clear, slaves had the sequential code, which we were using for serial runs, plus some extra PVM commands for information exchange. On the whole, slaves were communicating with their neigbours as well as with the master at used defined time steps. This actually is a classical approach.

My question is if I can use the same strategy (Master/Slave) with MPI? I also have a Poisson solver parallelized with MPI. But I could not see any slave spawning and running the same code on slave. Anyway, I am a little confused.

I appreciate any comment, refererence or small examples that you can tell me.

Thanks
  Reply With Quote

Old   November 6, 2008, 16:29
Default Re: Implementation of MPI
  #2
Ananda Himansu
Guest
 
Posts: n/a
In the most elementary approach to MPI, all the processes in a given communication group run the same (instruction) code, with different data (grids, initial conditions), i.e. SIMD approach. In this approach a single executable is launched as multiple processes by the "mpirun" script that is typically included in most MPI installations.

mpif90 -o myprog.exe myprog.f

mpirun -np=6 myprog.exe

I believe there are provisions in MPI for launching multiple (differing) executables that then communicate with each other. However, I stayed with the elementary approach, and simply used IF Blocks to implement the master/slave distinction when needed. Typically, I chose processor 0 (zero) as the master. For example, master sending messages to slave in a single source code:

call MPI_INIT(...)

call MPI_COMM_SIZE(MPI_COMM_WORLD, nprocs)

call MPI_COMM_RANK(MPI_COMM_WORLD, my_id)

... serial code ....

if (my_id) .eq. 0) then

do iproc = 1, nprocs-1

call MPI_ISEND(....)

end do

else

do iproc = 1, nprocs-1

call MPI_IRECV(....)

end do

end if

.... more serial code ....

call MPI_FINALIZE()

stop

end

I would check the online docs for the exact syntax of the MPI calls, because my memory is fuzzy on those.
  Reply With Quote

Old   November 6, 2008, 20:07
Default Re: Implementation of MPI
  #3
Ananda Himansu
Guest
 
Posts: n/a
Oops! I made a mistake. There should not have been a DO loop in the ELSE portion of the IF block. It should just be an MPI_IRECV(...) call there. Sorry for the confusion.

  Reply With Quote

Old   November 7, 2008, 03:14
Default Re: Implementation of MPI
  #4
Ertan Karaismail
Guest
 
Posts: n/a
Thanks for the quick reply Ananda. I guess I am understanding it better now. I will do some practice in the light of your suggestions. Hopefully, it will work..I'll let you know. thanks a lot

  Reply With Quote

Old   May 17, 2009, 12:29
Default please help me
  #5
New Member
 
noureddine
Join Date: May 2009
Posts: 4
Rep Power: 16
aspho_nour is on a distinguished road
Hello!

i have the same problem it means :i have a code writtin in fortran for a turbulent 3d incompressible flow by using MPICH2 (mpi2)+ ,
can you help me in order to advance in this work.

thanks
aspho_nour is offline   Reply With Quote

Old   May 17, 2009, 12:31
Default please help me
  #6
New Member
 
noureddine
Join Date: May 2009
Posts: 4
Rep Power: 16
aspho_nour is on a distinguished road
Hello!

i have the same problem it means :i have a code writtin in fortran for a turbulent 3d incompressible flow by using MPICH2 (mpi2)+ ,
can you help me in order to advance in this work.

if you want i send you my code.

thanks
aspho_nour is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
MPI error florencenawei OpenFOAM Installation 3 October 10, 2011 02:21
MPI implementation of OpenFOAM Jamshidi OpenFOAM 7 June 25, 2011 10:19
Error using LaunderGibsonRSTM on SGI ALTIX 4700 jaswi OpenFOAM 2 April 29, 2008 11:54
Is Testsuite on the way or not lakeat OpenFOAM Installation 6 April 28, 2008 12:12
MPI and parallel computation Wang Main CFD Forum 7 April 15, 2004 12:25


All times are GMT -4. The time now is 00:37.