M2R Parallel Systems

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Parallel Systems

General Informations

These lectures take place from 13:30 to 16:30 every Monday. The room locations are available here (look for PDES and then for the Parallel System lectures).

Here is a map of the campus for those who do not know where the rooms are.

The coordinator for these lectures is Arnaud Legrand. The lecturers are Vincent Danjean and Arnaud Legrand .


Today, parallel computing is omnipresent across a large spectrum of computing platforms. At the ``microscopic'' level, processor cores have used multiple functional units in concurrent and pipelined fashions for years, and multiple-core chips are now commonplace with a trend toward rapidly increasing numbers of cores per chip. At the ``macroscopic'' level, one can now build clusters of hundreds to thousands of individual (multi-core) computers. Such distributed-memory systems have become mainstream and affordable in the form of commodity clusters. Furthermore, advances in network technology and infrastructures have made it possible to aggregate parallel computing platforms across wide-area networks in so-called ``grids.'' The popularization of virtualization has allowed to consolidate workload and resource exploitation in ``clouds'' and raise many energy and efficiency issues.

An efficient exploitation of such platforms requires a deep understanding of both architecture, software and infrastructure mechanisms and of advanced algorithmic principles. The aim of this course is thus twofold. It aims at introducing the main trends and principles in the area of high performance computing infrastructures, illustrated by examples of the current state of the art. It intends to provide a rigorous yet accessible treatment of parallel algorithms, including theoretical models of parallel computation, parallel algorithm design for homogeneous and heterogeneous platforms, complexity and performance analysis, and fundamental notions of scheduling and work-stealing. These notions will always be presented in connection with real applications and platforms.

Course Organization

The course gives 6 credits (ECTS). In previous years, each student used to performs an individual performance evaluation study. Now that the MOSIG comprises a series of lectures on Performance Evaluation, this does not need to be done anymore solely in the context of the Parallel Systems lecture. There will be an exam at the end of the year and an extra lecture will be devoted to study together one of the exam of the previous years.

Program and expected schedule

Check last year's schedule to get a foretaste.

  • 29 September 2014 (14:00 - 17:00): Vincent Danjean (E100) Introduction to parallel computing. High Performance Architectures Processors (superscalar, simultaneous multi-threading, multi-core, GPU…). Symmetric MultiProcessors. OS features for cluster computing Multi-threading. Cache-aware vs. cache-oblivious algorithms.
  • 6 October 2014 (13:30 - 16:30): Vincent Danjean (C010) How to Efficiently Program High Performance Architectures ? Classical HPC API: MPI, pthreads, openMPI, CUDA, openCL, …
  • 13 October 2014 (13:30 - 16:30): Vincent Danjean (H104) End of the previous lecture…
    • Expexted work: Your next lecture with Vincent will be in the end of November. In the meantime, you should play with MPI on G5K: First, you may want to have a look at the following documents to know how to run an MPI code on G5K (look in the wiki and at the Cheat Sheet). Then, there are two possible options that do not illustrate the same issues. I suggest to start with the first one on sorting and later, once I have explained you the basics of parallel matrix multiplication algorithms give a try to the second one:
      1. Practical session on performance evaluation of parallel programs. PC_par_sort.pdf, parsort-1.0.tar.gz, mpi_sort.c This session is great for understanding the problems of measurement and parallel speedup. This kind of aspects is partially adressed in the Performance evaluation lecture but with multi-threaded code so you can compare between the two approaches.
      2. Double broadcast parallel matrix multiplication 07_MPI_tutorial.tgz This session is great for understanding the data movements and distribution in an SPMD program and the power of collective communication operations. You'll probably need to have seen the lectures on Parallel algorithms first.
  • 20 October 2014 (13:30 - 16:30): Arnaud Legrand (H104) Simple communication models, parallel algorithms on a ring and on a grid. The key notions are speedup/efficiency, Amhdal's law, pipelining, changing granularity to improve efficiency, and searching for sequential time in parallel algorithms.
  • 3 November 2014 (13:30 - 16:30): Arnaud Legrand (H104) Moving from basic SPMD parallel programs to more complex ones with dependencies and where load-balancing is non trivial. Playing with granularity and data distribution to improve performance.
    • Documents: slides PC_02_parallel_algorithms.pdf and 'Task Graphs and Parallel Tasks from Outer Space' section in this set of slides (physical pages 44 to 60 – Bernstein condition and application at compile time by openMP or at run time by StarPU, OmpSS, …)
    • References: This set of slides is huge and self-content. There is no need to dig further.
  • 10 November 2014 (13:30 - 16:30): Arnaud Legrand (H104) Modeling parallel programs and platforms. Fundamental characteristics: Work and Depth. Dataflow graph representation of an execution. BSP programs. Introduction to Scheduling (physical pages 28 to 129). We illustrated in detail the list scheduling technique and how the notion of critical path (or depth) was impacting the performance of schedules.
  • 17 November 2014 (09:30-12:45): Vincent Danjean From parallelism-aware algorithms to parallelism-oblivious algorithm. Work, depth and work-stealing. Illustration with a real implementation of such technique.
  • 24 November 2014 (09:30-12:45): Vincent Danjean Work-stealing and data locality. Sorting and merging, FFT, matrix operations. Adaptive algorithms and cascading divide & conquer: prefix computation, data compression, linear system solving
  • 1 December 2014 (9:30-12:45): Arnaud Legrand From fine-grain to coarse-grain. PRAM, sorting networks and application to implementation on NOWs.
    • Documents: PC_05_theory.pdf (you need to read and understand the whole set of slides, even those on FFT that have not been presented during the lecture; they are very similar in essence to the sorting networks and are thus a good exercise)
  • 8 December 2014 (9:30-12:45): Arnaud Legrand Hype and trends: cloud computing and how Virtualization changed the Grid perspective, exascale computing and how energy issues changed the HPC perspective.
  • 15 December 2014 (9:30-12:45): Arnaud Legrand Recent challenges and trends in HPC linear algebra: a recap on the whole lecture.
  • 16 January 2015 (9:30-11:30): Arnaud Legrand Looking together at 2014's exam and possibly 2013's exam.


All you need to know is in the large set of slides.