.TH MPI_Abort 3 "6/24/2006" "LAM/MPI 7.1.4" "LAM/MPI"
.SH NAME
MPI_Abort \-  Terminates MPI execution environment 
.SH SYNOPSIS
.nf
#include <mpi.h>
int MPI_Abort(MPI_Comm comm, int errcode)
.fi
.SH INPUT PARAMETERS
.PD 0
.TP
.B comm 
- communicator of tasks to abort 
.PD 1
.PD 0
.TP
.B errcode 
- error code to return to invoking environment 
.PD 1

.SH NOTES

Makes a "best attempt" to terminate all MPI processes associated with
the communicator 
.I comm
; for non-IMPI jobs, this will terminate all
processes.  
.I MPI_Abort
will hang, however, if the LAM daemon on the
node on which a rank was running has died.  For example, if a node
gets powered off in the middle of an MPI run and 
.I MPI_Abort
is
invoked, it may hang trying to contact the LAM daemon on the downed
node.

In the case of an IMPI job, in addition to terminating all local IMPI
procs, this function will also send an abort message to the local IMPI
host, which will, in turn send "closing" messages to all the other
IMPI hosts.  Their behavior upon receipt of these "closing" messages
is implementation dependant.

If the LAM IMPI host receives a premature "closing" message from a
remote IMPI host, it will attempt to continue processing.  Any new
messages to that host will likely hang, however.

.SH 'ERRCODE' IS SPLIT INTO THREE SECTIONS

.PD 0
.TP
.B lower 8 bits: error class
- . next 9 bits: function enumeration (there are over 300 MPI functions;
it takes 9 bits to represent all possibilities)
.PD 1
.PD 0
.TP
.B upper 15 bits: error code
- 
If the error class is nonzero, the error code is the POSIX return
value for the program (i.e., exit(error_code) is eventually called to
terminate the program).  If the error class is zero, 
.I errcode
is
returned as the POSIX return value for the program.
.PD 1

This is mainly because 
.I MPI_Abort
is used internally in LAM/MPI to
abort MPI upon error; LAM packs all three pieces of data into the
errcode.  Users who wish to return a specific value from the program
.SH SHOULD USE SOMETHING SIMILAR TO

.nf
return ((return_code << 17) + 1);
.fi


.SH NOTES FOR FORTRAN

All MPI routines in Fortran (except for 
.I MPI_WTIME
and 
.I MPI_WTICK
)
have an additional argument 
.I ierr
at the end of the argument list.
.I ierr
is an integer and has the same meaning as the return value of
the routine in C.  In Fortran, MPI routines are subroutines, and are
invoked with the 
.I call
statement.

All MPI objects (e.g., 
.I MPI_Datatype
, 
.I MPI_Comm
) are of type
.I INTEGER
in Fortran.

.SH MORE INFORMATION

For more information, please see the official MPI Forum web site,
which contains the text of both the MPI-1 and MPI-2 standards.  These
documents contain detailed information about each MPI function (most
of which is not duplicated in these man pages).

.I http://www.mpi-forum.org/


.SH ACKNOWLEDGEMENTS

The LAM Team would like the thank the MPICH Team for the handy program
to generate man pages ("doctext" from
.I ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz
), the initial
formatting, and some initial text for most of the MPI-1 man pages.
.SH LOCATION
abort.c