Abstract
We investigate a parallelization strategy for dense matrix factorization (DMF) algorithms, using OpenMP, that departs from the legacy (or conventional) solution, which simply extracts concurrency from a multi-threaded version of basic linear algebra subroutines (BLAS). The proposed approach is also different from the more sophisticated runtime-based implementations, which decompose the operation into tasks and identify dependencies via directives and runtime support. Instead, our strategy attains high performance by explicitly embedding a static look-ahead technique into the DMF code, in order to overcome the performance bottleneck of the panel factorization, and realizing the trailing update via a cache-aware multi-threaded implementation of the BLAS. Although the parallel algorithms are specified with a high level of abstraction, the actual implementation can be easily derived from them, paving the road to deriving a high performance implementation of a considerable fraction of linear algebra package (LAPACK) functionality on any multicore platform with an OpenMP-like runtime.
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Notes
Version from October 2017. Available online at http://www.argobots.org.
Abbreviations
- API:
-
Application programming interface.
- BLAS:
-
Basic linear algebra subroutines.
- BLIS:
-
BLAS-like library instatiation software framework.
- DLA:
-
Dense linear algebra.
- DMF:
-
Dense matrix factorization.
- GEMM:
-
General matrix-matrix multiplication.
- GLT:
-
Unified API for lightweight thread libraries.
- GLTO:
-
OpenMP implementation of GLT.
- LA MB G:
-
DMF algorithm linked with GNUs runtime.
- LA MB S:
-
DMF algorithm linked with Intels runtime.
- LAPACK:
-
Linear algebra package.
- LWT:
-
Lightweight threads library.
- MKL:
-
Intel math kernel library.
- MTB:
-
Multi-threaded BLAS parallelism exploitation.
- MTL:
-
Multi-threaded BLAS implementation.
- RTM:
-
Runtime task parallelism exploitation.
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Acknowledgements
The researchers from Universidad Jaume I were supported by the CICYT Projects TIN2014-53495-R and TIN2017-82972-R of the MINECO and FEDER, and the H2020 EU FETHPC Project 671602 “INTERTWinE”. The researchers from Universidad Complutense de Madrid were supported by the CICYT Project TIN2015-65277-R of the MINECO and FEDER. Sandra Catalán was supported during part of this time by the FPU program of the Ministerio de Educación, Cultura y Deporte. Adrián Castelló was supported by the ValI+D 2015 FPI program of the Generalitat Valenciana.
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Catalán, S., Castelló, A., Igual, F.D. et al. Programming parallel dense matrix factorizations with look-ahead and OpenMP. Cluster Comput 23, 359–375 (2020). https://doi.org/10.1007/s10586-019-02927-z
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DOI: https://doi.org/10.1007/s10586-019-02927-z