mpijava(1)

NAME
mpijava -- Open MPI Java wrapper compiler

SYNTAX
mpijava [-showme|-showme:compile|-showme:link] ...

OPTIONS

--showme
    This option comes in several different variants (see below). None of the variants invokes the underlying compiler; they all provide information on how the underlying compiler would have been invoked had --showme not been used. The basic --showme option outputs the command line that would be executed to compile the program. NOTE: If a non-filename argument is passed on the command line, the -showme option will not display any additional flags. For example, both "mpijava --showme" and "mpijava --showme my_source.java" will show all the wrapper-supplied flags. But "mpijava --showme -v" will only show the underlying compiler name and "-v".

--showme:compile
    Output the compiler flags that would have been supplied to the java compiler.

--showme:link
    Output the linker flags that would have been supplied to the java compiler.

--showme:command
    Outputs the underlying java compiler command (which may be one or more tokens).

--showme:incdirs
    Outputs a space-delimited (but otherwise undecorated) list of directories that the wrapper compiler would have provided to the underlying java compiler to indicate where relevant header files are located.

--showme:libdirs
    Outputs a space-delimited (but otherwise undecorated) list of directories that the wrapper compiler would have provided to the underlying linker to indicate where relevant libraries are located.

--showme:libs
    Outputs a space-delimited (but otherwise undecorated) list of library names that the wrapper compiler would have used to link an application. For example: "mpi open-rte open-pal util".

--showme:version
    Outputs the version number of Open MPI.

See the man page for your underlying java compiler for other options that can be passed through mpijava.

DESCRIPTION

Conceptually, the role of these commands is quite simple: transparently add relevant compiler and linker flags to the user's command line that are necessary to compile / link Open MPI programs, and then invoke the underlying compiler to actually perform the command.

As such, these commands are frequently referred to as "wrapper" compilers because they do not actually compile or link applications themselves; they only add in command line flags and invoke the back-end compiler.

  Overview
mpijava is a convenience wrapper for the underlying java compiler. Translation of an Open MPI program requires the linkage of the Open MPI-specific libraries which may not reside in one of the standard search directories of ld(1). It also often requires the inclusion of header files what may also not be found in a standard location.

mpijava passes its arguments to the underlying java compiler along with the -I, -L and -l options required by Open MPI programs.

The Open MPI Team strongly encourages using the wrapper compilers instead of attempting to link to the Open MPI libraries manually. This allows the specific implementation of Open MPI to change without forcing changes to linker directives in users' Makefiles. Indeed, the specific set of flags and libraries used by the wrapper compilers depends on how Open MPI was configured and built; the values can change between different installations of the same version of Open MPI.

Indeed, since the wrappers are simply thin shells on top of an underlying compiler, there are very, very few compelling reasons not to use mpijava. When it is not possible to use the wrappers directly, the -showme:compile and -showme:link options should be used to determine what flags the wrappers would have used.

NOTES

It is possible to make the wrapper compilers multi-lib aware. That is, the libraries and includes specified may differ based on the compiler flags specified (for example, with the GNU compilers on Linux, a different library path may be used if -m32 is seen versus -m64 being seen). This is not the default behavior in a standard build, but can be activated (for example, in a binary package providing both 32 and 64 bit support). More information can be found at:

  https://svn.open-mpi.org/trac/ompi/wiki/compilerwrapper3264

FILES

The string that the wrapper compilers insert into the command line before invoking the underlying compiler are stored in a text file created by Open MPI and installed to $pkgdata/mpijava-wrapper-data.txt, where $pkgdata is typically $prefix/share/openmpi, and $prefix is the top installation directory of Open MPI.

It is rarely necessary to edit this file, but it can be examined to gain insight into what flags the wrappers are placing on the command line.

ENVIRONMENT VARIABLES

By default, the wrappers use the compilers that were selected when Open MPI was configured. These compilers were either found automatically by Open MPI's "configure" script, or were selected by the user in the CC, CXX, F77, JAVAC, and/or FC environment variables before "configure" was invoked. Additionally, other arguments specific to the compiler may have been selected by configure.