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

Provided by: pvm-dev_3.4.5-12.5ubuntu1_amd64

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 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.

       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 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 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