Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
MPI_Buffer_detach(3)		      MPI		  MPI_Buffer_detach(3)

NAME
       MPI_Buffer_detach  -   Removes an existing buffer (for use in MPI_Bsend
       etc)

SYNOPSIS
       int MPI_Buffer_detach(void *buffer_addr,	int *size)

       int MPI_Buffer_detach_c(void *buffer_addr, MPI_Count *size)

OUTPUT PARAMETERS
       buffer_addr
	      -	initial	buffer address (choice)
       size   -	buffer size, in	bytes (integer)

NOTES
       The reason that MPI_Buffer_detach returns the address and size  of  the
       buffer  being  detached is to allow nested libraries to replace and re-
       store the buffer.  For example, consider

       int size, mysize, idummy;
       void *ptr, *myptr, *dummy;
       MPI_Buffer_detach(&ptr, &size);
       MPI_Buffer_attach(myptr,	mysize);
       .
       .
       .
       .
       .
       .
       library code ...
       .
       .
       .
       MPI_Buffer_detach(&dummy, &idummy);
       MPI_Buffer_attach(ptr, size);

       This is much like the action of the Unix	signal	routine	 and  has  the
       same  strengths (it is simple) and weaknesses (it only works for	nested
       usages).

       Note that for this approach  to	work,  MPI_Buffer_detach  must	return
       MPI_SUCCESS  even  when there is	no buffer to detach.  In that case, it
       returns a size of zero.	The MPI	 1.1  standard	for  MPI_BUFFER_DETACH
       contains	the text

       The statements made in this section describe the	behavior of MPI	for
       buffered-mode sends. When no buffer is currently	associated, MPI	behaves
       as if a zero-sized buffer is associated with the	process.

       This  could  be	read  as  applying only	to the various Bsend routines.
       This  implementation  takes  the	 position   that   this	  applies   to
       MPI_BUFFER_DETACH as well.

THREAD AND INTERRUPT SAFETY
       The  user  is responsible for ensuring that multiple threads do not try
       to update the same MPI object from  different  threads.	 This  routine
       should not be used from within a	signal handler.

       The MPI standard	defined	a thread-safe interface	but this does not mean
       that all	routines may be	called without any thread locks.  For example,
       two  threads  must  not	attempt	 to  change  the  contents of the same
       MPI_Info	object concurrently.  The user is responsible in this case for
       using some mechanism, such as thread locks, to  ensure  that  only  one
       thread  at  a  time  makes use of this routine.	Because	the buffer for
       buffered	sends (e.g., MPI_Bsend	)  is  shared  by  all	threads	 in  a
       process,	the user is responsible	for ensuring that only one thread at a
       time calls this routine or MPI_Buffer_attach .

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.

       The  Fortran  binding  for  this	routine	is different.  Because Fortran
       does not	have pointers, it is impossible	to provide a way  to  use  the
       output  of  this	 routine  to exchange buffers.	In this	case, only the
       size field is set.

NOTES FOR C
       Even though the bufferptr argument is declared as void *	, it is	really
       the address of a	void pointer.  See the rationale in the	 standard  for
       more details.

ERRORS
       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.  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 MPI_Comm_set_errhandler (for com-
       municators), MPI_File_set_errhandler (for files),  and  MPI_Win_set_er-
       rhandler	 (for  RMA windows).  The MPI-1	routine	MPI_Errhandler_set may
       be used but its	use  is	 deprecated.   The  predefined	error  handler
       MPI_ERRORS_RETURN  may  be  used	 to cause error	values to be returned.
       Note that MPI does not guarantee	that an	MPI program can	continue  past
       an  error;  however, MPI	implementations	will attempt to	continue when-
       ever possible.

       MPI_SUCCESS
	      -	No error; MPI routine completed	successfully.
       MPI_ERR_ARG
	      -	Invalid	argument.  Some	argument is invalid and	is not identi-
	      fied by a	specific error class (e.g., MPI_ERR_RANK ).
       MPI_ERR_OTHER
	      -	Other error; use  MPI_Error_string  to	get  more  information
	      about this error code.

SEE ALSO
       MPI_Buffer_attach

				   2/3/2025		  MPI_Buffer_detach(3)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=MPI_Buffer_detach&sektion=3&manpath=FreeBSD+Ports+14.3.quarterly>

home | help