pvm_freezegroup(3) Freezes dynamic group membership and caches info locally


C int info = pvm_freezegroup( char *group , int size)
Fortran call pvmffreezegroup( group, size, info )


Character string group name of an existing group.
Size of the group when it is frozen
size of group on success. Values less than 0 indicate and error.


The routine pvm_freezegroup makes a dynamic group named group static. The group information is then "cached" by all group members. pvm_freezegroup is a synchronizing routine and must be called by all group members to complete. size indicates the size the dynamic group should be when made static. A value of -1 indicates that the current size of the group should be used. info returns error information.

Once a dynamic group has been frozen with pvm_freezegroup , all subsequent operations that can be satisfied with local data use the locally held information. For processes that are outside of the group, the first group call, e.g., pvm_bcast(), will cause the static group information to be copied to the calling process. Subsequent operations then use the local information. Barriers are still arbitrated by the group server.

Group members should call pvm_lvgroup to leave the group and free any allocated structures that hold the group information. Processes not in the group may call pvm_lvgroup to free any locally allocated structures. In this case, an error code of PvmNotInGroup or PvmNoGroup will be returned to the caller.

Barrier are always arbitrated by the group server, even if the group has been made static with pvm_freezegroup. If a process leaves a static group while other process are waiting at a barrier, then PvmNoGroup is returned to all processes waiting at the barrier. Future barrier calls with the defunct static group, return the same error.


        inum = pvm_joingroup("worker");
        info = pvm_freezegroup( "worker", size );

        CALL PVMFJOINGROUP('group2', inum)
        CALL PVMFFREEZEGROUP( 'group2', size, info )


These error conditions can be returned by pvm_freezegroup
pvmd was not started or has crashed.
giving a NULL group name.
trying to freeze a group that is already frozen.
trying to freeze a group that you are not in.


There is no way to unfreeze a group.

Processes are not notified if a frozen group becomes invalid.

Having a non-member process call pvm_lvgroup to free structures is a bit strange.