Node-Level Performance Engineering @ Uni Köln

Topic outline

• 

  General

  This course covers performance engineering approaches on the compute node level. Even application developers who are fluent in OpenMP and MPI often lack a good grasp of how much performance could at best be achieved by their code. This is because parallelism takes us only half the way to good performance. Even worse, slow serial code tends to scale very well, hiding the fact that resources are wasted. This course conveys the required knowledge to develop a thorough understanding of the interactions between software and hardware. This process must start at the core, socket, and node level, where the code gets executed that does the actual computational work. We introduce the basic architectural features and bottlenecks of modern processors and compute nodes. Pipelining, SIMD, superscalarity, caches, memory interfaces, ccNUMA, etc., are covered. A cornerstone of node-level performance analysis is the Roofline model, which is introduced in due detail and applied to various examples from computational science. We also show how simple software tools can be used to acquire knowledge about the system, run code in a reproducible way, and validate hypotheses about resource consumption. Finally, once the architectural requirements of a code are understood and correlated with performance measurements, the potential benefit of code changes can often be predicted, replacing hope-for-the-best optimizations by a scientific process.

  
  

  Time: January 20-22, 2020

  Place: TBA

  
  

  Preliminary agenda:

  
  

  Monday, January 20

  13:00-13:30	Welcome & Intro
  13:30-14:30	Basic computer architecture
  14:30-15:00	Tools I: topology & affinity
  15:00-15:15	Coffee break
  15:15-16:15	Hands-on: simple benchmarks
  16:15-17:00	Microbenchmarking

  
  
  

  
  

  Tuesday, January 21

  09:00-10:30	Roofline model basics
  10:30-10:45	Coffee break
  10:45-11:30	Tools II: hardware performance counters
  11:30-12:00	Hands-on: dense MVM
  12:00-14:00	Lunch break
  14:00-14:30	Hands-on cont'd
  14:30-15:30	Programming for SIMD & ccNUMA
  15:30-15:45	Coffee break
  15:45-17:00	Hands-on

  
  
  

  
  

  Wednesday, January 22

  09:00-10:30	Roofline case studies I
  10:30-10:45	Coffee break
  10:45-12:00	Roofline case studies II
  12:00-12:30	Basic skills for Performance Engineering
  12:30-13:30	Lunch break
  13:30-15:30	Hands-on: code analysis
  15:30-15:45	Coffee break
  15:45-17:00	Outlook: the ECM performance model

  
  
  
• 

  Day 1

  • General introduction File
  • Modern Computer Architecture File
  • Performance Tools 1: Topology and Affinity File
  • Microbenchmarking (additional slides) File
  • 
    

    
    

  • Exercise 1: simple benchmarks Page
• 

  Day 2

  • Introduction to the Roofline model File
  • Using hardware performance counters with LIKWID File
  • SIMD File
  • ccNUMA File
  •  

    
    

  • Exercise 2: dense matrix-vector multiplication Page
• 

  Day 3

  • Roofline case studies File
  • Performance Engineering Basics File
  • The ECM performance model File
  • References File
  • 
    

    
    

  • Exercise 3: General code optimization Page
  • Exercise 4: a 3D stencil Page
• 

  Additional Material

  For publications of the RRZE HPC group, see https://hpc.fau.de/research/publications/

  Our HPC book (second edition coming up in 2020): Hager & Wellein: Introduction to High Performance Computing for Scientists and Engineers

  Important links:

  Intel® 64 and IA-32 Architectures Optimization Reference Manual

  LIKWID tool suite: https://github.com/RRZE-HPC/likwid

  LIKWID documentation Wiki: http://tiny.cc/LIKWID

  LIKWID quick reference sheet

  Kerncraft automatic Roofline/ECM modeling tool: https://github.com/RRZE-HPC/kerncraft

  Online layer condition calculator: https://rrze-hpc.github.io/layer-condition/#calculator