.TH MPI_Init_thread 3 "2/22/2022" " " "MPI"
.SH NAME
MPI_Init_thread \-  Initialize the MPI execution environment 
.SH SYNOPSIS
.nf
int MPI_Init_thread(int *argc, char ***argv, int required, int *provided)
.fi
.SH INPUT PARAMETERS
.PD 0
.TP
.B required 
- desired level of thread support (integer)
.PD 1

.SH INPUT/OUTPUT PARAMETERS
.PD 0
.TP
.B argc 
- argc (None)
.PD 1
.PD 0
.TP
.B argv 
- argv (None)
.PD 1

.SH OUTPUT PARAMETERS
.PD 0
.TP
.B provided 
- provided level of thread support (integer)
.PD 1

.SH COMMAND LINE ARGUMENTS
MPI specifies no command-line arguments but does allow an MPI
implementation to make use of them.  See 
.I MPI_INIT
for a description of
the command line arguments supported by 
.I MPI_INIT
and 
.I MPI_INIT_THREAD
\&.


.SH NOTES
The valid values for the level of thread support are:
.PD 0
.TP
.B MPI_THREAD_SINGLE 
- Only one thread will execute.
.PD 1
.PD 0
.TP
.B MPI_THREAD_FUNNELED 
- The process may be multi-threaded, but only the main
thread will make MPI calls (all MPI calls are funneled to the
main thread).
.PD 1
.PD 0
.TP
.B MPI_THREAD_SERIALIZED 
- The process may be multi-threaded, and multiple
threads may make MPI calls, but only one at a time: MPI calls are not
made concurrently from two distinct threads (all MPI calls are serialized).
.PD 1
.PD 0
.TP
.B MPI_THREAD_MULTIPLE 
- Multiple threads may call MPI, with no restrictions.
.PD 1

.SH NOTES FOR FORTRAN
Note that the Fortran binding for this routine does not have the 
.I argc
and
.I argv
arguments. (
.I MPI_INIT_THREAD(required, provided, ierror)
)

.SH ERRORS

All MPI routines (except 
.I MPI_Wtime
and 
.I MPI_Wtick
) return an error value;
C routines as the value of the function and Fortran routines in the last
argument.  Before the value is returned, the current MPI error handler is
called.  By default, this error handler aborts the MPI job.  The error handler
may be changed with 
.I MPI_Comm_set_errhandler
(for communicators),
.I MPI_File_set_errhandler
(for files), and 
.I MPI_Win_set_errhandler
(for
RMA windows).  The MPI-1 routine 
.I MPI_Errhandler_set
may be used but
its use is deprecated.  The predefined error handler
.I MPI_ERRORS_RETURN
may be used to cause error values to be returned.
Note that MPI does 
.B not
guarantee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
possible.

.PD 0
.TP
.B MPI_SUCCESS 
- No error; MPI routine completed successfully.
.PD 1

.PD 0
.TP
.B MPI_ERR_OTHER 
- Other error; use 
.I MPI_Error_string
to get more information
about this error code. 
.PD 1

.SH SEE ALSO
MPI_Init, MPI_Finalize
.br