Enabling OpenMPI on Linux

Question

I'm trying to enable OpenMPI on Ubuntu using CodeBlocks. I have already downloaded it using:

sudo apt-get install -y autotools-dev g++ build-essential openmpi1.6-bin openmpi1.6-doc libopenmpi1.6-dev

Afterwards I tried to run the following code:

#include <stdio.h>
#include <mpi.h>

int main(int argc, char **argv)
{
   int size, rank;
   MPI_Init(&argc, &argv);
   MPI_Comm_size(MPI_COMM_WORLD, &size);
   MPI_Comm_rank(MPI_COMM_WORLD, &rank);
   printf("SIZE = %d RANK = %d\n",size,rank);
   MPI_Finalize();   
   return(0);
}

But I got this error:

fatal error: mpi.h: No such file or directory

Then I changed the c++ compiler from g++ to mpicxx as it's recommended here: FAQ: Compiling MPI.
But when I try to run my code now, I get the following bunch of errors:

openmpi.cpp|| undefined reference to `MPI_Init'|
openmpi.cpp|| undefined reference to `ompi_mpi_comm_world'|
openmpi.cpp|| undefined reference to `MPI_Comm_size'|
openmpi.cpp|| undefined reference to `ompi_mpi_comm_world'|
openmpi.cpp|| undefined reference to `MPI_Comm_rank'|
openmpi.cpp|| undefined reference to `MPI_Finalize'|
[...]

I assume, I have to add the Path or link the library, but I'm not sure how to achieve this. I also don't know where OpenMPI has been installed on my machine.
I have downloaded the folder from the website, as well, if that can help.

Update
After adding mpicxx to the linker and -pthread -L/opt/openmpi/lib -lmpi_cxx -lmpi -ldl -lm -Wl,--export-dynamic -lrt -lnsl -lutil -lm -ldl as additional flags, I finally can compile the code.
But now I get another error:

[[INVALID],INVALID] ORTE_ERROR_LOG: A system-required executable either could not be found or was not executable by this user in file ess_singleton_module_c at line 231
[...]
Soory! You were supposed to get help about:  
orte_init:startup:internal-failure  
But I couldn't open the file:  
/usr/share/openmpi/help-orte-runtime: No such file or directory.

You don't have to add the long list of options to the linker flags if you change the linker to mpicxx. Only add them if you keep the original linker, e.g. ld. — Hristo Iliev
– Hristo Iliev, Commented Nov 26, 2013 at 11:12

Hristo Iliev · Accepted Answer · 2013-11-26 08:31:25Z

2

Most MPI libraries come with special compiler wrappers, e.g.:

mpicc for the C compiler;
mpic++/mpiCC/mpicxx for the C++ compiler;
mpif77/mpif90/mpif95 for the Fortran compiler;
other distribution-specific wrappers, e.g. mpiicc for Intel MPI library with Intel C Compiler.

These wrappers provide all options that are needed by the compiler in order to find the include files and link the proper libraries.

Therefore you have to update your project settings and change both the compiler and the linker to mpicxx.

Another option would be to run the following command:

mpicxx -showme:link

It will give you a list of options that you should add to the linker flags in your project's settings in order to properly link the executable with Open MPI.

answered Nov 26, 2013 at 8:31

Hristo Iliev

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2 Comments

Hristo Iliev Over a year ago

@user1170330, I find it strange that you've added Ubuntu Open MPI packages via apt-get and yet the flags that you get from mpicxx -showme point to /opt/openmpi/lib. Packages supplied by the distribution usually have their files in /usr. Do you happen to have both system Open MPI packages and a version that you have compiled by yourself?

Hristo Iliev Over a year ago

Remove /opt/openmpi/bin from the path and use the libraries that come with the distribution.

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