DEGAS

DEGAS
File:Your-team-logo.png
Team Members	LBNL, Rice U., UC Berkeley, UT Austin, LLNL, NCSU
PI	Katherine Yelick (LBNL))
Co-PIs	Vivek Sarkar (Rice U.), James Demmel (UC Berkeley), Mattan Erez (UT Austin), Dan Quinlan (LLNL)
Website	team website
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Description about your project goes here.....

Team Members

• Lawrence Berkeley National Laboratory (LBNL)
• Rice University
• University of California, Berkeley
• University of Texas at Austin
• Lawrence Livermore National Laboratory (LLNL)
• North Carolina State University (NCSU)

Mission

Mission Statement: To ensure the broad success of Exascale systems through a unified programming model that is productive, scalable, portable, and interoperable, and meets the unique Exascale demands of energy efficiency and resilience.

Goals & Objectives

• Scalability: Billion‐way concurrency, thousand‐way on chip with new architectures
• Programmability: Convenient programming through a global address space and high‐level abstractions for parallelism, data movement and resilience
• Performance Portability: Ensure applications can be moved across diverse machines using implicit (automatic) compiler optimizations and runtime adaptation
• Resilience: Integrated language support for capturing state and recovering from faults
• Energy Efficiency: Avoid communication, which will dominate energy costs, and adapt to performance heterogeneity due to system-­‐level energy management
• Interoperability: Encourage use of languages and features through incremental adoption

Roadmap

Any Roadmap to be included?

Impact

Any Impact to be included?

Programming Models

Two Distinct Parallel Programming Questions

• What is the parallel control model?

• What is the model for sharing/communication?

=== Applications Drive New Programming Models

• Message Passing Programming
  • Divide up domain in pieces
  • Compute one piece and exchange
  • MPI and many libraries

• Global Address Space Programming
  • Each start computing
  • Grab whatever/whenever
  • UPC, CAF, X10, Chapel, Fortress, Titanium, GlobalArrays

Hierarchical Programming Model

File:DEGAS-Heirarchical-PM.png

• Goal: Programmability of exascale applications while providing scalability, locality, energy efficiency, resilience, and portability
  • Implicit constructs: parallel multidimensional loops, global distributed data structures, adaptation for performance heterogeneity
  • Explicit constructs: asynchronous tasks, phaser synchronization, locality

• Built on scalability, performance, and asynchrony of PGAS models
  • Language experience from UPC, Habanero‐C, Co‐Array Fortran, Titanium

• Both intra and inter‐node; focus is on node model

• Languages demonstrate DEGAS programming model
  • Habanero‐UPC: Habanero’s intra‐node model with UPC’s inter‐node model
  • Hierarchical Co‐Array Fortran (CAF): CAF for on‐chip scaling and more
  • Exploration of high level languages: E.g., Python extended with H‐PGAS

• Language‐independent H‐PGAS Features:
  • Hierarchical distributed arrays, asynchronous tasks, and compiler specialization for hybrid (task/loop) parallelism and heterogeneity
  • Semantic guarantees for deadlock avoidance, determinism, etc.
  • Asynchronous collectives, function shipping, and hierarchical places
  • End‐to‐end support for asynchrony (messaging, tasking, bandwidth utilization through concurrency)
  • Early concept exploration for applications and benchmarks