A scheduling processor assigns the work items to the execution engines for {TAIL ~ generation} of {HEAD ~ the gather entries} 
A scheduling processor assigns the work items to the execution engines for { TAIL ~ generation } of { HEAD ~ the gather entries }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD