Efficient Scheduling of DAGs and Sets of Chains on a Simple Asymmetric Multicore Model

Volleyball practice apparatus especially useful in training players in spiking the ball includes a lightweight, flexible support harness closely engaging and confining a volleyball, and a pair of flexible, elastically extensible lines having one end attached to the harness and their other end attached one to each of a pair of upwardly extending supports adjustably mounted on a lightweight structural frame adapted to be attached to the volleyball net to support the volleyball above and to one side of the net in position for spiking. The elastically extensible support lines permit the ball to be projected down and across the net in substantially the same manner as in spiking a free ball. The extensible lines then return the ball upward and back across the net into position to be spiked again.