RUNTIME SUPPORT AND COMPILATION METHODS FOR USER-SPECIFIED IRREGULAR DATA DISTRIBUTIONS

This paper describes two new ideas by which a High Performance Fortran compiler can deal with irregular computations effectively. The first mechanism invokes a user specified mapping procedure via a set of prop osed compiler directives. The directives allow use of program arrays t o describe graph connectivity, spatial location of array elements, and computational load. The second mechanism is a conservative method for compiling irregular loops in which dependence arises only due to redu ction operations. This mechanism in many cases enables a compiler to r ecognize that it is possible to reuse previously computed information from inspectors (e.g., communication schedules, loop iteration partiti ons, and information that associates off-processor data copies with on -processor buffer locations). This paper also presents performance res ults for these mechanisms from a Fortran 90D compiler implementation.