Tailoring a self-distributing architecture to a cluster computer environment

This paper analyzes the consequences of existing network structure for the design of a protocol for a radical COMA (Cache Only Memory Architecture). Parallel computing today faces two significant challenges: the difficulty of programming and the need to leverage existing "off-the-shelf" hardware. The difficulty of programming parallel computers can be split into two problems: distributing the data, and distributing the computation. Parallelizing compilers address both problems, but have limited application outside the domain of loop intensive "scientific" code. Conventional COMAs provide an adaptive, self-distributing solution to data distribution, but do not address computation distribution. Our proposal leverages parallelizing compilers, and then extends COMA to provide adaptive self-distribution of both data and computation. The radical COMA protocols can be implemented in hardware, software, or a combination of both. When, however, the implementation is constrained to operate in a cluster computing environment (that is, to use only existing, already installed hardware), the protocols have to be reengineered to accommodate the deficiencies of the hardware. This paper identifies the critical quantities of various existing network structures, and discusses their repercussions for protocol design. A new protocol is presented in detail.