Compiling for Shared-Memory and Message-Passing Computer

Many parallel languages presume a shared address space in which any portion of a computation can access any datum. Some parallel computers directly support this abstraction with hardware shared memory. Other computers provide distinct (per-processor) address spaces and communication mechanisms on which software can construct a shared address space. Since programmers have difficulty explicitly managing address spaces, there is considerable interest in compiler support for shared address spaces on the widely available messagepassing computers. At first glance, it might appear that hardware-implemented shared memory is unquestionably a better base on which to implement a language. This paper argues, however, that compiler-implemented shared memory, despite its shortcomings, has the potential to exploit more effectively the resources in a parallel computer. Hardware designers need to find mechanisms to combine the advantages of both approaches in a single system. Categories and Subject Des..