SIBLINGS(3PVM) PVM Version 3.4 SIBLINGS(3PVM)NAMEpvm_siblings - return the number and associated task ids of processes
that were started together in a single spawn call.
SYNOPSIS
C int ntids = pvm_siblings( int **tids )
Fortran call pvmfsiblings( ntids, index, sibling )
PARAMETERS
ntids Returns the number of tids that were spawned together. Value
less than 0 indicates an error.
tids Pointer to the array of tids that contains the siblings.
Indexed from 0 to (ntids - 1)
index Integer index of tid to be returned in sibling. If index is set
to -1, then sibling is unchanged. Otherwise, must be in the
range [0, ntids - 1]
sibling When index is in the range [0, ntids -1], this contains the tid
of the desired index.
DESCRIPTION
The routine pvm_siblings returns the number of tasks and a list of task
ids of processes that were spawned together in a single spawn call. The
spawning task multicasts the list of successful to the spawned tasks so
that each task has an identical copy of the sibling list. pvm_siblings
uses local storage to keep the list of tids and does not update this
list when sibling tasks exit the virtual machine. The FORTRAN version
allows calling programs read a particular index in the internal sibling
array. If pvm_siblings is successful, ntids will be > 0. If some
error occurs then ntids will be < 0.
pvm_siblings is designed to simplify the logic in static spmd-style
programs. By giving tasks an identical list of tids and its size, pro‐
grams may self size and treat the sibling as static map between
instances and tasks. The internal list is not updated when sibling
tasks exit the virtual machine and should be treated as a snapshot of
the parallel program when it was first started.
If a task was started by pvm_spawn, then pvm_siblings will return ntids
= 1 and
ntids = 1 and tids will contain a single entry identical to the task id
returned by pvm_mytid()EXAMPLES
C:
int *tids;
ntids = pvm_siblings(&tids);
Fortran:
INTEGER TIDS(0:MAXNPROC)
CALL PVMFSIBLINGS(NTIDS, -1, IDUM)
DO I = 0, NTIDS-1
CALL PVMFSIBLINGS(NTIDS, I, TIDS(I))
ERRORSpvm_siblings can return the following error codes
PvmNoTask
No task at that index, or index is invalid.
SEE ALSOpvm_spawn(3PVM), pvm_mytid(3PVM), pvm_parent(3PVM)
26 June, 1997 SIBLINGS(3PVM)
