MPI_Init_thread - Initialize the MPI execution environment
MPI_Init_thread(int *pargc, char ***pargv, int requested, int *pprovided)
pargc - Pointer to the number of arguments
pargv - Pointer to the argument vector
- Desired level of thread support
- Given level of thread support
LAM currently supports MPI_THREAD_SINGLE , MPI_THREAD_SERIALIZED , and
MPI_THREAD_FUNNELED . MPI_THREAD_MULTIPLE is not yet supported. The
use of MPI_INIT_THREAD is recommended instead of MPI_INIT if an MPI
program is going to be multi-threaded. However, the
LAM_MPI_THREAD_LEVEL environment variable can be used to the same
effect. See MPI_Init(3) for more details.
There is currently no distinction between MPI_THREAD_SINGLE and
MPI_THREAD_FUNNELED . An application using MPI_THREAD_FUNNELED
promises to never call MPI from a different thread than the one that
invoked MPI_INIT (or MPI_INIT_THREAD ). LAM does no checking to ensure
that this is true. As such, no locks are placed around MPI calls to
ensure that only one thread is making MPI calls at a time (since the
application has promised that only one thread will be making MPI
Using MPI_THREAD_SERIALIZED will cause LAM to place locks around all
MPI calls such that only one thread will be able to enter the MPI
library at a time; beware of this fact for portability with other MPI
implementations. Even with multiple threads, deadlock is still
possible when using MPI_THREAD_SERIALIZED -- applications still need to
be aware of this and code appropriately.
Other than this restriction, this function behaves identically to
MPI_INIT (see MPI_Init(3)).
Note that both MPI_INIT and MPI_INIT_THREAD are allowed to changed the
requested thread level based on lower-level device and SSI module
initializations. For example, if a user application invokes MPI_Init ,
some SSI modules may require threads and therefore upgrade the thread
support level to something higher than MPI_THREAD_SINGLE .
If an error occurs in an MPI function, the current MPI error handler is
called to handle it. By default, this error handler aborts the MPI
job. The error handler may be changed with MPI_Errhandler_set ; the
predefined error handler MPI_ERRORS_RETURN may be used to cause error
values to be returned (in C and Fortran; this error handler is less
useful in with the C++ MPI bindings. The predefined error handler
MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value
needs to be recovered). Note that MPI does not guarantee that an MPI
program can continue past an error.
All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
value; C routines as the value of the function and Fortran routines in
the last argument. The C++ bindings for MPI do not return error
values; instead, error values are communicated by throwing exceptions
of type MPI::Exception (but not by default). Exceptions are only
thrown if the error value is not MPI::SUCCESS .
Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI
functions will return upon an error, there will be no way to recover
what the actual error value was.
- No error; MPI routine completed successfully.
- Invalid argument. Some argument is invalid and is not
identified by a specific error class. This is typically a NULL
pointer or other such error.
- This error class is associated with an error code that
indicates that an attempt was made to call MPI_INIT a second
time. MPI_INIT may only be called once in a program.
- Other error; use MPI_Error_string to get more information
about this error code.
MPI_Init, MPI_Finalize, lamboot, mpirun, lamhalt, lamssi
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).
The LAM Team would like the thank the MPICH Team for the handy program
to generate man pages ("doctext" from
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.