.\" Man page generated from reStructuredText. . .TH "MPI_WIN_ALLOCATE_SHARED" "3" "Jul 22, 2024" "" "Open MPI" . .nr rst2man-indent-level 0 . .de1 rstReportMargin \\$1 \\n[an-margin] level \\n[rst2man-indent-level] level margin: \\n[rst2man-indent\\n[rst2man-indent-level]] - \\n[rst2man-indent0] \\n[rst2man-indent1] \\n[rst2man-indent2] .. .de1 INDENT .\" .rstReportMargin pre: . RS \\$1 . nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin] . nr rst2man-indent-level +1 .\" .rstReportMargin post: .. .de UNINDENT . RE .\" indent \\n[an-margin] .\" old: \\n[rst2man-indent\\n[rst2man-indent-level]] .nr rst2man-indent-level -1 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]] .in \\n[rst2man-indent\\n[rst2man-indent-level]]u .. .sp \fI\%MPI_Win_allocate_shared\fP — One\-sided MPI call that allocates shared memory and returns a window object for RMA operations. .SH SYNTAX .SS C Syntax .INDENT 0.0 .INDENT 3.5 .sp .nf .ft C #include int MPI_Win_allocate_shared (MPI_Aint size, int disp_unit, MPI_Info info, MPI_Comm comm, void *baseptr, MPI_Win *win) .ft P .fi .UNINDENT .UNINDENT .SS Fortran Syntax .INDENT 0.0 .INDENT 3.5 .sp .nf .ft C USE MPI ! or the older form: INCLUDE \(aqmpif.h\(aq MPI_WIN_ALLOCATE_SHARED(SIZE, DISP_UNIT, INFO, COMM, BASEPTR, WIN, IERROR) INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR INTEGER DISP_UNIT, INFO, COMM, WIN, IERROR .ft P .fi .UNINDENT .UNINDENT .SS Fortran 2008 Syntax .INDENT 0.0 .INDENT 3.5 .sp .nf .ft C USE mpi_f08 MPI_Win_allocate_shared(size, disp_unit, info, comm, baseptr, win, ierror) USE, INTRINSIC :: ISO_C_BINDING, ONLY : C_PTR INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: size INTEGER, INTENT(IN) :: disp_unit TYPE(MPI_Info), INTENT(IN) :: info TYPE(MPI_Comm), INTENT(IN) :: comm TYPE(C_PTR), INTENT(OUT) :: baseptr TYPE(MPI_Win), INTENT(OUT) :: win INTEGER, OPTIONAL, INTENT(OUT) :: ierror .ft P .fi .UNINDENT .UNINDENT .SH INPUT PARAMETERS .INDENT 0.0 .IP \(bu 2 \fBsize\fP: Size of window in bytes (nonnegative integer). .IP \(bu 2 \fBdisp_unit\fP: Local unit size for displacements, in bytes (positive integer). .IP \(bu 2 \fBinfo\fP: Info argument (handle). .IP \(bu 2 \fBcomm\fP: Communicator (handle). .UNINDENT .SH OUTPUT PARAMETERS .INDENT 0.0 .IP \(bu 2 \fBbaseptr\fP: Initial address of window. .IP \(bu 2 \fBwin\fP: Window object returned by the call (handle). .IP \(bu 2 \fBierror\fP: Fortran only: Error status (integer). .UNINDENT .SH DESCRIPTION .sp \fI\%MPI_Win_allocate_shared\fP is a collective call executed by all processes in the group of \fIcomm\fP\&. On each process, it allocates memory of at least \fIsize\fP bytes that is shared among all processes in \fIcomm\fP, and returns a pointer to the locally allocated segment in \fIbaseptr\fP that can be used for load/store accesses on the calling process. The locally allocated memory can be the target of load/store accesses by remote processes; the base pointers for other processes can be queried using the function \fI\%MPI_Win_shared_query\fP\&. The call also returns a window object that can be used by all processes in \fIcomm\fP to perform RMA operations. The \fIsize\fP argument may be different at each process and \fIsize\fP = 0 is valid. It is the user’s responsibility to ensure that the communicator \fIcomm\fP represents a group of processes that can create a shared memory segment that can be accessed by all processes in the group. The discussions of rationales for \fI\%MPI_Alloc_mem\fP and \fI\%MPI_Free_mem\fP in MPI\-3.1 section 8.2 also apply to \fI\%MPI_Win_allocate_shared\fP; in particular, see the rationale in MPI\-3.1 section 8.2 for an explanation of the type used for \fIbaseptr\fP\&. The allocated memory is contiguous across process ranks unless the info key \fIalloc_shared_noncontig\fP is specified. Contiguous across process ranks means that the first address in the memory segment of process i is consecutive with the last address in the memory segment of process i \- 1. This may enable the user to calculate remote address offsets with local information only. .sp The following info keys are supported: .INDENT 0.0 .TP .B alloc_shared_noncontig If not set to \fItrue\fP, the allocation strategy is to allocate contiguous memory across process ranks. This may limit the performance on some architectures because it does not allow the implementation to modify the data layout (e.g., padding to reduce access latency). .TP .B blocking_fence If set to \fItrue\fP, the osc/sm component will use \fI\%MPI_Barrier\fP for \fI\%MPI_Win_fence\fP\&. If set to \fIfalse\fP a condition variable and counter will be used instead. The default value is \fIfalse\fP\&. This info key is Open MPI specific. .UNINDENT .sp For additional supported info keys see \fI\%MPI_Win_create\fP\&. .SH NOTES .sp Common choices for \fIdisp_unit\fP are 1 (no scaling), and (in C syntax) \fIsizeof(type)\fP, for a window that consists of an array of elements of type \fItype\fP\&. The later choice will allow one to use array indices in RMA calls, and have those scaled correctly to byte displacements, even in a heterogeneous environment. .sp Calling \fI\%MPI_Win_free\fP will deallocate the memory allocated by \fI\%MPI_Win_allocate_shared\fP\&. It is thus erroneous to manually free \fIbaseptr\fP\&. .SH C NOTES .sp While \fIbaseptr\fP is a \fBvoid *\fP type, this is to allow easy use of any pointer object for this parameter. This argument is really a \fBvoid **\fP type. .SH ERRORS .sp Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument. .sp Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before \fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions. .sp Open MPI includes three predefined error handlers that can be used: .INDENT 0.0 .IP \(bu 2 \fBMPI_ERRORS_ARE_FATAL\fP Causes the program to abort all connected MPI processes. .IP \(bu 2 \fBMPI_ERRORS_ABORT\fP An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if \fI\%MPI_Abort\fP was called on that communicator. If called on a window or file, acts as if \fI\%MPI_Abort\fP was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process. .IP \(bu 2 \fBMPI_ERRORS_RETURN\fP Returns an error code to the application. .UNINDENT .sp MPI applications can also implement their own error handlers by calling: .INDENT 0.0 .IP \(bu 2 \fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP .IP \(bu 2 \fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP .IP \(bu 2 \fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP .IP \(bu 2 \fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP .UNINDENT .sp Note that MPI does not guarantee that an MPI program can continue past an error. .sp See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&. .sp See the Error Handling section of the MPI\-3.1 standard for more information. .sp \fBSEE ALSO:\fP .INDENT 0.0 .INDENT 3.5 .INDENT 0.0 .IP \(bu 2 \fI\%MPI_Alloc_mem\fP .IP \(bu 2 \fI\%MPI_Free_mem\fP .IP \(bu 2 \fI\%MPI_Win_allocate\fP .IP \(bu 2 \fI\%MPI_Win_create\fP .IP \(bu 2 \fI\%MPI_Win_shared_query\fP .IP \(bu 2 \fI\%MPI_Win_free\fP .UNINDENT .UNINDENT .UNINDENT .SH COPYRIGHT 2003-2024, The Open MPI Community .\" Generated by docutils manpage writer. .