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¶
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)