[rootxblade08 ~]# mpif77 -v
Using built-in specs.
Target: i386-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-libgcj-multifile --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi --enable-plugin --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic --host=i386-redhat-linux
Thread model: posix
gcc version 4.1.2 20071124 (Red Hat 4.1.2-41)

Steven wrote:
> Hi Tim:
>  
> Thanks for your response!

>  
> I checked mpif77. It seems provided by openmpi.
>  

> 
> Since I am testing openmpi, I would like keep its Fortran compiler. How can I know the largest data type supported? And which modification is needed for me?
>  

You should be able to verify which compilers were used for your openmpi, e.g.
mpif77 -v
As mpif77 would be just a wrapper, the actual compiler (g95, or a gfortran 
of the last 2 years, or a commercial Fortran?) should also be present on 
that system.  In order to make a lam mpif77 with the same Fortran 
extensions, you would need to configure and build lam with the same 
Fortran compiler.