Quantitatively Assessing Performance Portability with Roofline

Event Sponsor: 
Exascale Computing Project
Start Date: 
Dec 13 2018 - 10:25am
John Pennycook, Intel
Charlene Yang, NERSC
Jack Deslippe, NERSC
Osni Marques

The IDEAS Productivity project, in partnership with the DOE Computing Facilities of the ALCF, OLCF, and NERSC and the DOE Exascale Computing Project (ECP) has resumed the webinar series on Best Practices for HPC Software Developers, which we began in 2016.

As part of this series, we offer one-hour webinars on topics in scientific software development and high-performance computing, approximately once a month. The next webinar is titled Quantitatively Assessing Performance Portability with Roofline, and will be presented by John Pennycook (Intel), Charlene Yang (Lawrence Berkeley National Laboratory) and Jack Deslippe (Lawrence Berkeley National Laboratory). The webinar will take place on Wednesday, January 23, 2019 at 1:00 pm ET.


Wouldn’t it be great if we could port a code to a new high-performance architecture without substantially changing the code yet achieving a similar level of performance as hand-optimized code? This webinar will frame the discussion around ‘performance portability’, why it is important and desirable, and how to quantitatively measure it. The webinar will start with a background check on how the concept of performance portability came about and past attempts to define it and quantify it. Then we will introduce a simple yet powerful metric and an empirical methodology to quantitatively assess a code’s performance portability across multiple platforms. The methodology uses the Roofline performance model to measure an ‘architectural efficiency’ term in the metric proposed by Pennycook et al. We will dive into a few nuances of this methodology, for example, how and why empirical ceilings should be used for performance bounds, how to accurately account for complex instructions such as divides, how to model strided memory accesses, and how to select the appropriate Roofline ceilings and application performance points to make sure that the performance portability analysis is not erroneously skewed. We will also show some results of measuring performance portability using the aforementioned metric and methodology on two modern architectures, Intel Xeon Phi and NVIDIA V100 GPUs. 

The webinar will be conducted with WebEx. You will receive a confirmation email with the connection details the day before the webinar. (Note that spam filters occasionally flag this type e-mail, preventing it from going into the Inbox and redirecting it to Spam.)

Miscellaneous Information: 

Connection Information:

The webinar will be hosted via WebEx.  We will open the WebEx session at least 20 minutes prior to the start of the webinar. We recommend you connect as early as possible to ensure you do not encounter technical difficulties in seeing and/or hearing the webinar.  Once the webinar begins, it will be difficult to provide technical assistance.