mpid_lpidmask.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`\_}Lpidmask}{tex}{10/7/2002}
\manname{MPID{\tt \char`\_}Lpidmask}
--- Description of the Processor mask data strucure 
\subhead{Synopsis}
\startvb\begin{verbatim}
typedef struct {
    /* other, device-specific information */
    /* Typically int pidbits[MPID_MAX_PROCS_BY_INT] */
} MPID_Lpidmask;

\end{verbatim}
\endvb
Allows quick determination whether a designated processor is within the
set of active processes.
\par
A typical implementation is a bitvector.
\par
This is used to help manage datatypes for remote memory operations (for
efficient implementation of {\tt MPI{\tt \char`\_}Put}, {\tt MPI{\tt \char`\_}Get}, or {\tt MPI{\tt \char`\_}Accumulate
}when using nontrivial datatypes, it is necessary to cache a copy of the
datatype on the remote process.  Using a processor mask makes it easy to
check whether a remote process already has a copy of a particular MPI
datatype).
\par
Note that groups can not use processor masks because groups need ordering
information (e.g., pid 0 might have rank in the group of 245).
\par
This structure is manipulated with the routines:
\begin{verbatim}
  void MPID_Lpid_set( MPID_Lpidmask *, int pid )
  void MPID_Lpid_init( MPID_Lpidmask * )
  int MPID_Lpid_isset( MPID_Lpidmask *, int pid )
  int MPID_Lpid_nextset( MPID_Lpidmask *, int lastpid ) 
\end{verbatim}

\par
\subhead{Module}
Group-DS
\endmanpage