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<H1 id="MPI_Win_shared_query">MPI_Win_shared_query</H1>
Query the size and base pointer for a patch of a shared memory window.
<H2>Synopsis</H2>
<PRE>
int MPI_Win_shared_query(MPI_Win win, int rank, MPI_Aint * size, int *disp_unit, void *baseptr)
</PRE>
<P>
This function queries the process-local address for remote memory segments
created with <tt>MPI_Win_allocate_shared</tt>. This function can return different
process-local addresses for the same physical memory on different processes.
<P>
The returned memory can be used for load/store accesses subject to the
constraints defined in MPI 3.0, Section 11.7. This function can only be called
with windows of type <tt>MPI_Win_flavor_shared</tt>. If the passed window is not of
flavor <tt>MPI_Win_flavor_shared</tt>, the error <tt>MPI_ERR_RMA_FLAVOR</tt> is raised. When rank
is <tt>MPI_PROC_NULL</tt>, the pointer, disp_unit, and size returned are the pointer,
disp_unit, and size of the memory segment belonging the lowest rank that
specified size > 0. If all processes in the group attached to the window
specified size = 0, then the call returns size = 0 and a baseptr as if
<tt>MPI_Alloc_mem</tt> was called with size = 0.
<P>
<H2>Input Parameters</H2>
<DL>
<DT><B>win </B> <DD> window object used for communication (handle)
<DT><B>rank </B> <DD> target rank
</DL>
<P>
<H2>Output Parameters</H2>
<DL>
<DT><B>size </B> <DD> size of the segment at the given rank
<DT><B>disp_unit </B> <DD> local unit size for displacements, in bytes (positive integer)
<DT><B>baseptr </B> <DD> base pointer in the calling process' address space of the shared
segment belonging to the target rank.
</DL>
<P>
<H2>Thread and Interrupt Safety</H2>
<P>
This routine is thread-safe. This means that this routine may be
safely used by multiple threads without the need for any user-provided
thread locks. However, the routine is not interrupt safe. Typically,
this is due to the use of memory allocation routines such as <tt>malloc
</tt>or other non-MPICH runtime routines that are themselves not interrupt-safe.
<P>
<H2>Notes for Fortran</H2>
All MPI routines in Fortran (except for <tt>MPI_WTIME</tt> and <tt>MPI_WTICK</tt>) have
an additional argument <tt>ierr</tt> at the end of the argument list. <tt>ierr
</tt>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
<tt>call</tt> statement.
<P>
All MPI objects (e.g., <tt>MPI_Datatype</tt>, <tt>MPI_Comm</tt>) are of type <tt>INTEGER
</tt>in Fortran.
<P>
<H2>Errors</H2>
<P>
All MPI routines (except <tt>MPI_Wtime</tt> and <tt>MPI_Wtick</tt>) 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 <tt>MPI_Comm_set_errhandler</tt> (for communicators),
<tt>MPI_File_set_errhandler</tt> (for files), and <tt>MPI_Win_set_errhandler</tt> (for
RMA windows). The MPI-1 routine <tt>MPI_Errhandler_set</tt> may be used but
its use is deprecated. The predefined error handler
<tt>MPI_ERRORS_RETURN</tt> may be used to cause error values to be returned.
Note that MPI does <em>not</em> guarentee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
possible.
<P>
<DL>
<DT><B>MPI_SUCCESS </B> <DD> No error; MPI routine completed successfully.
</DL>
<DL>
<DT><B>MPI_ERR_ARG </B> <DD> Invalid argument. Some argument is invalid and is not
identified by a specific error class (e.g., <tt>MPI_ERR_RANK</tt>).
</DL>
<DL>
<DT><B>MPI_ERR_RANK </B> <DD> Invalid source or destination rank. Ranks must be between
zero and the size of the communicator minus one; ranks in a receive
(<tt>MPI_Recv</tt>, <tt>MPI_Irecv</tt>, <tt>MPI_Sendrecv</tt>, etc.) may also be <tt>MPI_ANY_SOURCE</tt>.
</DL>
<DL>
<DT><B>MPI_ERR_WIN </B> <DD> Invalid MPI window object
</DL>
<P>
<H2>See Also</H2>
MPI_Win_allocate_shared
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