There is an excellent article on how to build OpenMPI Libraries for 64-bit integers. For more detailed information, do look at How to build MPI libraries for 64-bit integers

The information on this website is taken from the above site.

Step 1: Check the integer size. Do the following. If the output is as below, you have to compile OpenMPI with 64 bits.

# ompi_info -a | grep 'Fort integer size'
Fort integer size: 4

Intel Compilers Step 2a: To compile OpenMPI with Intel Compilers and with 64-bits integers, do the following:

# ./configure --prefix=/usr/local/openmpi CXX=icpc CC=icc 
F77=ifort FC=ifort FFLAGS=-i8 FCFLAGS=-i8
# make -j 8
# make install

* GNU Compilers

Step 2b: To compile OpenMPI with GNU Compilers and with 64-bits, do the followings:

# ./configure --prefix=/usr/local/openmpi CXX=g++ CC=gcc F77=gfortran FC=gfortran \
FFLAGS="-m64 -fdefault-integer-8"       \
CFLAGS="-m64 -fdefault-integer-8"      \
CFLAGS=-m64                             \
CXXFLAGS=-m64
# make -j 8
# make install

Step 3: Update your PATH and LD_LIBRARY_PATH in your .bashrc

export $PATH=/usr/local/openmpi/bin:$PATH 
export $LD_LIBRARY_PATH=/usr/local/openmpi/lib:$LD_LIBRARY_PATH

Verify that the installation is correct

# ompi_info -a | grep 'Fort integer size' 
Fort integer size: 8