NAME

       MPIL_Type_id -  LAM/MPI-specific function to return the type ID of an MPI datatype

SYNOPSIS

       #include <mpi.h>
       int MPIL_Type_id(MPI_Datatype dtype, int *ptid)

INPUT PARAMETER

       dtype  - MPI datatype (handle)

OUTPUT PARAMETER

       ptid   - datatype ID (integer)

NOTES

       In  the  LAM  implementation  of  MPI, each communicator has an integer context ID associated with it for
       synchronizing on different contexts.  This ID is global to all the processes in the communicator's group,
       and  uniquely  identifies  that  communicator  for each process.  These properties allow the processes to
       safely exchange messages without interference from operations on other communicators.

       The MPI standard does not provide a way  to  access/view  this  implementation-dependent  synchronization
       since communicators are opaque objects.  Users do not need such access for normal MPI operations.  On the
       other hand, when debugging MPI applications, the  opaque  nature  of  communicators  hinders  the  user's
       efforts.   This  is  especially true on fully observable systems such as LAM, where users can monitor the
       full state of the processes and message queues, which includes the context ID (see mpitask (1) and mpimsg
       (1)).

       This  is  a LAM/MPI-specific function and is intended mainly for debugging.  If this function is used, it
       should be used in conjunction with the LAM_MPI C preprocessor macro

       #if LAM_MPI
       int tid
       MPIL_Type_id(MPI_INT, &tid);
       #endif

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
       end of the argument list.  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 call statement.

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

ERRORS

       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.
       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_TYPE
              - Invalid datatype argument.  May be an uncommitted MPI_Datatype (see MPI_Type_commit ).
       MPI_ERR_ARG
              -  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.

SEE ALSO

       MPIL_Comm_gps, MPIL_Comm_id

LOCATION

       mpil_id.c