SCATTER(3PVM)							  PVM Version 3.4						     SCATTER(3PVM)

NAME

       pvm_scatter - Sends to each member of a group a section of an array from a specified member of the group.

SYNOPSIS

       C    int info = pvm_scatter( void *result, void *data,
			 int count, int datatype, int msgtag,
			 char *group, int rootginst)

       Fortran	  call pvmfscatter(result, data, count, datatype,
				  msgtag, group, rootginst, info)

PARAMETERS

       result  Pointer to the starting address of an array of length count of datatype which will be overwritten by the message from the specified
	       root member of the group.

       data    On the root this is a pointer to the starting address of an array datatype of local values which are to be distributed to the  mem-
	       bers  of  the group.  If n is the number of members in the group, then this array of datatype should be of length at least n*count.
	       This argument is meaningful only on the root.

       count   Integer specifying the number of elements of datatype to be sent to each member of the group from the root.

       datatype
	       Integer specifying the type of the entries in the result and data arrays.  (See below for defined types.)

       msgtag  Integer message tag supplied by the user.  msgtag should be >= 0.  It allows the user's program to  distinguish	between  different
	       kinds of messages.

       group   Character string group name of an existing group.

       rootginst
	       Integer instance number of group member who performs the scatter of its array to the members of the group.

       info    Integer status code returned by the routine.  Values less than zero indicate an error.

DESCRIPTION

       pvm_scatter() performs a scatter of data from the specified root member of the group to each of the members of the group, including itself.
       All group members must call pvm_scatter(), each receives a portion of the data array from the root in their local result array.	It  is	as
       if  the	root node sends to the ith member of the group count elements from its array data starting at offset i*count from the beginning of
       the data array.	And, it is as if, each member of the group performs a corresponding receive of count values of datatype  into  its  result
       array.  The root task is identified by its instance number in the group.

       C and Fortran defined datatypes are:
		  C datatypes	FORTRAN datatypes
		-----------------------------------
		  PVM_BYTE	 BYTE1
		  PVM_SHORT	 INTEGER2
		  PVM_INT	 INTEGER4
		  PVM_FLOAT	 REAL4
		  PVM_CPLX	 COMPLEX8
		  PVM_DOUBLE	 REAL8
		  PVM_DCPLX	 COMPLEX16
		  PVM_LONG

       In  using the scatter and gather routines, keep in mind that C stores multidimensional arrays in row order, typically starting with an ini-
       tial index of 0; whereas, Fortran stores arrays in column order, typically starting with an offset of 1.

       The current algorithm is very simple and robust.  A future implementation may make more efficient use of the architecture to allow  greater
       parallelism.

EXAMPLES

       C:
	  info =  pvm_scatter(&getmyrow, &matrix, 10, PVM_INT,
			     msgtag, "workers", rootginst);

       Fortran:
	  CALL PVMFSCATTER(GETMYCOLUMN, MATRIX, COUNT, INTEGER4,
	 &		  MTAG, 'workers', ROOT, INFO)

ERRORS

       These error conditions can be returned by pvm_scatter

       PvmNoInst
	      Calling task is not in the group

       PvmBadParam
	      The datatype specified is not appropriate

       PvmSysErr
	      Pvm system error

SEE ALSO

       pvm_bcast(3PVM), pvm_barrier(3PVM), pvm_psend(3PVM)

								  21 April, 1994						     SCATTER(3PVM)