Processor Lower Bound Formulas for Array Computations and Parametric Diophantine Systems

  • Authors:
  • Affiliations:
  • Venue:
  • IPPS '98 Proceedings of the 12th. International Parallel Processing Symposium on International Parallel Processing Symposium
  • Year:
  • 1998

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Abstract

Using a directed acyclic graph (dag) model of algorithms, we solve a problem related to precedence-constrained multiprocessor schedules for array computations: Given a sequence of dags and linear schedules parametrized by n, compute a lower bound on the number of processors required by the schedule as a function of n. In our formulation, the number of tasks that are scheduled for execution during any fixed time step is the number of non-negative integer solutions dn to a set of parametric linear Diophantine equations. We illustrate an algorithm based on generating functions for constructing a formula for these numbers dn. The algorithm has been implemented as a Mathematica program. An example run and the symbolic formula for processor lower bounds automatically produced by the algorithm for Gaussian Elimination is presented.