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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 speci-
	     fied 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 members
	     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.

     datatypeInteger  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  in-
     stance 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 multi-
     dimensional  arrays  in row order, typically starting with an initial 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  paral-
     lelism.

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)

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