Category News

SIAM CSE’13 talks

Aparna and Jee are at SIAM CSE 2013 in Boston this week, giving talks the fast multipole method and the energy roofline, respectively. (UPDATE: Click on the title for Jee’s talk to access the PDF slides.)

Tech report: Energy rooflines

Rooflines in time vs. "archlines" in energy

Rooflines in time vs. “archlines” in energy

Check out our new technical report, which presents a thought-experiment on the question of whether engineering an algorithm to optimize time differs from doing so with respect to energy (e.g., Joules).

  • Jee Whan Choi, Richard Vuduc. “A roofline model of energy.” Technical report no. GT-CSE-12-01, Georgia Institute of Technology, School of Computational Science and Engineering, Atlanta, GA, USA, December 2012. [PDF (452 KiB)]


We describe an energy-based analogue of the time-based roofline model of Williams, Waterman, and Patterson (Comm. ACM, 2009). Our goal is to explain—in simple, analytic terms accessible to algorithm designers and performance tuners—how the time, energy, and power to execute an algorithm relate. The model considers an algorithm in terms of operations, concurrency, and memory traffic; and a machine in terms of the time and energy costs per operation or per word of communica- tion. We confirm the basic form of the model experimentally. From this model, we suggest under what conditions we ought to expect an algorithmic time-energy trade-off, and show how algorithm properties may help inform power management.

Subject area: High-Performance Computing
Keywords: performance analysis; power and energy modeling; computational intensity; machine balance; roofline model

Note (January 14, 2013): The above link to the PDF now points to the official version on the Georgia Tech Library’s report repository. If you downloaded an earlier version (dated December 24, 2012), you may wish to re-download this newer version. (The only difference is the addition of Appendix B, made on December 31, 2012.)

Bon voyage, Hana.

The HPC Garage bids a warm “adieu” to Hana Strakova, who visited from the University of Vienna this semester. She’s doing some interesting new work on algorithmic resilience using gossip-based methods. Best of luck upon your return, Hana, it was great having you around this semester!

Photo: Rich and Hana

Rich and fall semester intern, Hana (University of Vienna)

Synthesis Lecture on GPUs

Our Morgan & Claypool Synthesis Lecture on GPGPU performance analysis is now available! (Most libraries should have proxy access; the book is $30 otherwise, DRM-free.)

GT @ SC’12

The Georgia Tech both at Supercomputing 2012

The happy faces of Georgia Tech HPC at Supercomputing 2012. Please drop by!

The HPC Garage is at Supercomputing 2012! We are here with the rest of the Georgia Tech crew, which overall has a great presence at SC; see the list of talks and birds-of-a-feather sessions at

CSE Seminar: Energy “rooflines”

We are kicking off the CSE seminar this week, with a short “ideas” talk on the relationship among the time, energy, and power required by an algorithm. This talk features new work by Jee on the energy-based analogue of the time-based roofline model (of Williams, Patterson, and Waterman in CACM, 2009).

You can get the slides hereUpdate: You can also watch the talk here.

VECPAR’12 + K Supercomputer

Rich at the K Supercomputer facility in Kobe, Japan

Rich at the K Supercomputer facility in Kobe, Japan


Rich has the pleasure of being at the 10th International Meeting on High-Performance Computing for Computational Science (VECPAR), held this year at RIKEN AICS research facility in Kōbe (神戸市), Japan. RIKEN is home of the amazing K Supercomputer, shown here (only partly obstructed by Rich’s head, which he wishes had as much computing power).

Rich is especially grateful to the VECPAR organizers and other hosts (here, here, here, and here, among others) for the chance to speak, to see the K Computer, and to sample Kobe beef (yes, it’s that good!). For those interested in the talk, here is a link to Rich’s slides: [PDF].

Autotuning @ iWAPT’12

Speaker and audience at iWAPT'12 in Kobe, Japan

Live at iWAPT’12. Photo courtesy of Prof. Kengo Nakajima.

Rich is in Kōbe (神戸市), Japan to take part in the International Workshop on Automatic Performance Tuning (iWAPT), which is the 7th in this series of Japanese-run meetings. He had the honor of serving as this year’s iWAPT PC chair. Many thanks to co-chair Prof. Takeshi Iwashita and the program committee members for selecting a nice selection of papers.

Visiting Tsubame 2.0

Rich is in Japan this week, shown here feeling small against the backdrop of Tsubame 2.0, the petascale GPU-based supercomputer at the Tokyo Institute of Technology. The cost-performance ratio—and the associated engineering design needed to get there—is impressive. Interestingly, every undergrad at Tokyo Tech gets an account on the system, which is a big step toward democratizing HPC. Many thanks to Prof. Satoshi Matsuokafor taking the time out of his hectic schedule to offer a tour. (On a Japanese holiday, no less!)

Rich @ Tsubame 2.0

Rich @ Tsubame 2.0 at the Tokyo Institute of Technology. Photo courtesy of Prof. Satoshi Matusoka, Tsubame’s lead architect.

Jee is power-man with PowerMon!

Jee is bringing The HPC Garage one step closer toward being an actual garage! Here he is taking some fine-grained power measurements using PowerMon 2.0, a cool device for taking DC power measurements. PowerMon 2.0 is the work of some of the fine folks at RENCI.

Jee, posing with our local PowerMon setup

Jee is PowerMan! (with PowerMon)

This work is part of our study to determine the precise relationships between computational time and energy. (Thanks, Jee, for putting up with my insistence that we document this event. — Rich)