[hpc-announce] Numerical Reproducibility at Exascale Workshop

Francesco Silvestri silvest1 at dei.unipd.it
Mon Jun 29 16:25:54 CDT 2015

Numerical Reproducibility at Exascale Workshop (NRE2015)

Taking place at SC15, Austin, Texas

Friday morning, November 20, 2015

Web: http://www.nist.gov/itl/ssd/is/numreprod2015.cfm

Submit: https://easychair.org/conferences/?conf=nre2015

Deadline: August 16, 2015

Notification: September 14, 2015

Camera-ready: October 08, 2015

Organized by: Walid Keyrouz (NIST) and Michael Mascagni (FSU & NIST)

Call for Participation

Experimental reproducibility is a cornerstone of the scientific
method.  As computing has grown into a powerful tool for scientific
inquiry, computational reproducibility has been one of the core
assumptions underlying scientific computing.  With "traditional"
single-core CPUs, documenting a numerical result was relatively
straightforward.  However, hardware developments over the past several
decades have made it almost impossible to ensure computational
reproducibility or to even fully document a computation without
incurring a severe loss of performance.  This loss of reproducibility
started with CPUs that used out-of-order execution to improve
performance.  It has accelerated with recent architectural trends
towards platforms with increasingly large numbers of processing
elements, namely multicore CPUs and compute accelerators (GPUs, Intel
Xeon Phi, FPGAs).

Programmers targeting these platforms rely on tools and libraries to
produce codes or execute them efficiently.  As a result, codes can run
efficiently, but have execution details that can be impossible to
predict and are often very difficult to understand after execution.
Furthermore, parallel implementations often result in code with
varying execution orders between runs, leading to non-reproducible
computations.  The underlying reasons are that (1) the hardware and
system software allocate parallel work in ways that are not always
specifiable at compile time and (2) the execution often proceeds in an
opportunistic manner with the execution order changing between runs.
As such, floating-point computations, which are not commutative and
associative, can have different execution orders and execute on
different processing elements between runs, leading to runs with
varying results as a matter of fact.  The predictability of systems is
further complicated by two issues that are becoming more critical as
systems grow in scale: (1) interconnect systems with latencies that
are often outside the control of programmers and (2) reliability as
the mean time between failure (MTBF) is now measured in hours on large
systems.  This situation seriously affects the ability to rely on
scientific computations as a metrological substitute for

Workshop Scope

The workshop is meant to address the scope of the problems of
numerical reproducibility in HPC in general and those anticipated as
we scale to Exascale machines in the next decade.  We seek
contributions of short papers (3--4 pages) in the areas of
computational reproducibility in HPC from academic, government, and
industry stakeholders.  Areas of interest include, but are not limited

- Case studies of reproducibility or the lack of it
- Reproducibility issues in current HPC
- System-level solutions
- Algorithmic solutions
- Software solutions
- Uncertainty quantification in computational reproducibility
- Fundamental numerical analysis of reproducibility
- Future prospects

Workshop Format

The workshop will have:

- two plenary talks with authors TBD,
- a morning of contributed talks, and
- a panel discussion to summarize the problem, current research, and
  prospects on long-term solutions.

The talks for this workshop will be refereed and a selection of
submissions will be invited to submit full papers for peer-reviewed
publication through ACM/IEEE SIGHPC.


Submissions of up to four pages should be formatted according to the
IEEE conference format
and submitted as a PDF document using Easychair at

Travel Support

Some limited travel support may be available.

Important Dates

- August 16, 2015: paper submission deadline
- September 14, 2015: acceptance notifications to authors and
  invitations to submit full papers
- October 08, 2015: submission deadline of camera-ready full papers


- Walid Keyrouz, National Institute of Standards and Technology (NIST), USA
- Michael Mascagni, National Institute of Standards and Technology
  (NIST) and Florida State University, USA

Steering Committee

- Dong H. Ahn, Lawrence Livermore National Lab, USA
- David Bailey, UC Davis, USA
- Michela Becchi, University of Missouri, USA
- David R. C. Hill, Université Blaise Pascal, Clermont-Ferrand, France
- Walid Keyrouz (co-organizer), NIST, USA
- Xiaoye Sherry Li, Lawrence Berkeley National Laboratory, USA
- Michael Mascagni (co-organizer), FSU & NIST, USA
- Nathalie Revol, INRIA/ENS-Lyon, France
- Siegfried Rump, University of Hamburg, Germany


E-mail: numerical.reproducibility.at.nist.gov (replace ".at." by "@")

More information about the hpc-announce mailing list