Additionally, the code for implementing the PMPI interface is done through #define's.
Depending on the platform, it happens either as Clement describes (with #defines for MPI_Foo --> PMPI_Foo) or if the platform doesn't support weak symbols (e.g., MacOS), the source code for the C API functions is essentially compiled twice: 1. once as "normal" 2. a second time with #define MPI_Foo PMPI_Foo (for all values of Foo) > On Mar 4, 2019, at 12:33 PM, Clement Foyer <clement.fo...@gmail.com> wrote: > > Hi, > > The reason you cannot find it is because it actually is not define as such. > The PMPI interface is defined as the profiling interface. The principle is > you have the real symbol in your shared library that is PMPI_Send, with a > weak alias being MPI_Send. So, if a third party want to intercept calls to > MPI_Send (as an example, to count how many times this function is called), he > just need to provide its own library that present the MPI_Send symbol, does > its work (e.g., increment some counter to keep track of how many times this > function was called by the user), and then call the PMPI_Send function > provided by Open MPI. As the ompi symbol for MPI_Send is defined as weak, it > won’t collide with the already defined symbol and thus simply be ignored > instead of rising a warning at link time. > > Note: in order to have the third party library loaded in time such as its > MPI_Send symbol is considered and not the Open MPI one, you need to set your > LD_PRELOAD variable accordingly. > > You would end up with user code calling MPI_Send provided by third party, > calling PMPI_Send provided by the Open MPI library. Without this third party > library, you have user code that call MPI_Send which is actually an alias for > PMPI_Send provided by Open MPI library. > > There might be some other implications, but I may let the people more > proficient than myself explain them :) > > Regards, > Clément > > On 04/03/2019, 16:45, "devel on behalf of vishakha patil" > <mailto:devel-boun...@lists.open-mpi.org on behalf of > mailto:pvishakha.offic...@gmail.com> wrote: > > Hi, > > Greetings for the day! > > I am a MTech(Computer) student of Savitribai Phule Pune University, > Maharashtra, India. > For my project purpose I have downloaded nightly snapshot tarball of openmpi > v4.0.x series. > It got build successfully. But while traversing the code (manually as well as > using cscope) I am not able to find the implementation of PMPI_* (PMPI_Send > etc) which is getting called from MPI_Send function of send.c file. > I have gone through the readme and make files but not able to find it. Could > you please help me with the same? > It is required to get complete understanding of openmpi algorithms as it is > part of my MTech project. > > Please let me know if any other details required. Thank you! > > Regards, > Vishakha > > _______________________________________________ devel mailing list > devel@lists.open-mpi.org https://lists.open-mpi.org/mailman/listinfo/devel > > > _______________________________________________ > devel mailing list > devel@lists.open-mpi.org > https://lists.open-mpi.org/mailman/listinfo/devel -- Jeff Squyres jsquy...@cisco.com _______________________________________________ devel mailing list devel@lists.open-mpi.org https://lists.open-mpi.org/mailman/listinfo/devel
