A technique for executing pixel shader programs is provided. The pixel shader programs are executed in workgroups, which allows access by work-items to a local data store and also allows program synchronization at barrier points. Utilizing workgroups allows for more flexible and efficient execution than previous implementations in the pixel shader stage. Several techniques for assigning fragments to wavefronts and workgroups are also provided. The techniques differ in the degree of geometric locality of fragments within wavefronts and/or workgroups. In some techniques, a greater degree of locality is enforced, which reduces processing unit occupancy but also reduces program complexity. In other techniques, a lower degree of locality is enforced, which increases processing unit occupancy.