mpid_comm.tex

刚才是说明 现在是安装程序在 LINUX环境下进行编程的MPICH安装文件

\startmanpage
\mantitle{MPID{\tt \char`\_}Comm}{tex}{10/7/2002}
\manname{MPID{\tt \char`\_}Comm}
--- Description of the Communicator data structure 
\subhead{Synopsis}
\startvb\begin{verbatim}
typedef struct { 
    int           handle;        /* value of MPI_Comm for this structure */
    volatile int ref_count;
    int16_t       context_id;    /* Assigned context id */
    int           remote_size;   /* Value of MPI_Comm_(remote)_size */
    int           local_size;    /* Value of MPI_Comm_size */
    int           rank;          /* Value of MPI_Comm_rank */
    MPID_VC *(*virtural connection)[]; /* Virtual connection table */
    MPID_Comm_kind_t comm_kind;  /* MPID_INTRACOMM or MPID_INTERCOMM */
    MPID_List     attributes;    /* List of attributes */
    MPID_Group    *local_group,  /* Groups in communicator. */
                  *remote_group; /* The local and remote groups are the
                                 same for intra communicators */
    char          name[MPI_MAX_OBJECT_NAME];  /* Required for MPI-2 */
    MPID_Errhandler *errhandler;  /* Pointer to the error handler structure */
    struct MPID_Collops_struct  *coll_fns;    /* Pointer to a table of 
                                            functions implementing the 
                                            collective routines */
  /* other, device-specific information */
#ifdef MPID_DEV_COMM_DECL
    MPID_DEV_COMM_DECL
#endif
} MPID_Comm;

\end{verbatim}
\endvb

\subhead{Notes}
Note that the size and rank duplicate data in the groups that
make up this communicator.  These are used often enough that this
optimization is valuable.
\par
The virtual connection table is an explicit member of this structure.
This contains the information used to contact a particular process,
indexed by the rank relative to this communicator.
\par
Groups are allocated lazily.  That is, the group pointers may be
null, created only when needed by a routine such as {\tt MPI{\tt \char`\_}Comm{\tt \char`\_}group}.
The local process ids needed to form the group are available within
the virtual connection table.
For intercommunicators, we may want to always have the groups.  If not,
we either need the {\tt local{\tt \char`\_}group} or we need a virtual connection table
corresponding to the {\tt local{\tt \char`\_}group} (we may want this anyway to simplify
the implementation of the intercommunicator collective routines).
\par
The pointer to the structure containing pointers to the collective
routines allows an implementation to replace each routine on a
routine-by-routine basis.  By default, this pointer is null, as are the
pointers within the structure.  If either pointer is null, the implementation
uses the generic provided implementation.  This choice, rather than
initializing the table with pointers to all of the collective routines,
is made to reduce the space used in the communicators and to eliminate the
need to include the implementation of all collective routines in all MPI
executables, even if the routines are not used.
\par
\par
\subhead{Module}
Communicator-DS
\par
\par
\subhead{Question}
For fault tolerance, do we want to have a standard field for communicator
health?  For example, ok, failure detected, all (live) members of failed
communicator have acked.
\endmanpage