1. A computer apparatus, said computer apparatus comprising, a first physical node, said first physical node comprising a first processor and a first subset of a main memory associated therewith; a second physical node, said second physical node comprising a second processor and a second subset of said main memory associated therewith, said first and second subsets of said main memory being disjoint, said first processor and said second processor being capable of accessing main memory in any node of said computer apparatus, said first processor accessing said first subset of main memory more efficiently than it accesses main memory not belonging to said first subset of main memory, said second processor accessing said second subset of main memory more efficiently than it accesses main memory not belonging to said second subset of main memory; a thread, said thread being capable of executing on either of said physical nodes; and a logical node to which said thread is assigned, said logical node being specified when said thread is created, said logical node being converted to said first physical node or to said second physical node independently of assigning said thread to said logical node such that said thread can be provided with nodal affinity for a specified node without the need to specify a particular physical node to which said thread is assigned; wherein said computer apparatus supports concurrent execution of a plurality of jobs, a first job of said plurality of jobs having at least one respective thread, and a second job of said plurality of jobs having multiple respective threads; and wherein said computer apparatus supports grouping said at least one respective thread of said first job and at least one thread of said plurality of respective threads of said second job into a first group of a plurality of groups, said at least one respective thread of said first job and said at least one thread of said plurality of respective threads of said second job being grouped independently of their association with said first job and said second job, said first group being assigned to said logical node, wherein said first group contains fewer than all said threads of said first job and said second job.