Reducing the I/O Volume in Sparse Out-of-core Multifrontal Methods

  • Authors:
  • Emmanuel Agullo;Abdou Guermouche;Jean-Yves L'Excellent

  • Affiliations:
  • Emmanuel.Agullo@inria.fr and Jean-Yves.L.Excellent@ens-lyon.fr;Abdou.Guermouche@labri.fr;-

  • Venue:
  • SIAM Journal on Scientific Computing
  • Year:
  • 2010

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Abstract

Sparse direct solvers, and in particular multifrontal methods, are methods of choice to solve the large sparse systems of linear equations arising in certain simulation problems. However, they require a large amount of memory (e.g., in comparison to iterative methods). In this context, out-of-core solvers may be employed: disks are used when the required storage exceeds the available physical memory. In this paper, we show how to process the task dependency graph of multifrontal methods in a way that minimizes the input/output (I/O) requirements. From a theoretical point of view, we show that minimizing the storage requirement can lead to a huge volume of I/O compared to directly minimizing the I/O volume. Then experiments on large real-world problems also show that applying standard algorithms to minimize the storage is not always efficient at reducing the volume of I/O and that significant gains can be obtained with the use of our algorithms to minimize I/O. We finally show that efficient memory management algorithms can be applied to all the variants proposed.