tion that the effective control paths and data dependencies are, for all intents and purposes, opaque to compilers used to build the applications (an interesting analysis is presented in Mitchell et al. 3). Applications often simultaneously deploy what is viewed as distinct functional idioms in application development. Manipulation of dynamic and persistent databases, functionality implemented via remote servers or peers, event-based programming, graphical processing, other compute-intensive processing (of many flavors), and more occur in many modern client applications (that is, applications you might be running on your laptop).

Moreover, multi-language development has become far less surprising for the past two decades. Driven recently by Web-based application development (and most likely to be continued by parallel software development), the last 15 years or so have seen new programming languages successfully adopted commercially at a rate of approximately one every 18 months. Consider Java, C#, JavaScript, PHP, Perl, Python, Ruby, Erlang, OCaml, and Haskell, to name a few. Call it a Moore’s Law analogy for programming tools (driven this time by the economics of software development rather than silicon manufacturing). This may also surprise many, especially C or C++ developers.

Productivity is one of the primary drivers of software development technology, usually even more of a factor than performance. For many market segments, time to market or deployment is the biggest influencer of tool use. Productivity is also another way to quantify development costs. It is be-

The trend toward
increasing software
abstraction and
heterogeneity to
manage complexity
is accelerating.

cause of this emphasis on productivity that we are not at a plateau; instead, the trend toward increasing software abstraction and heterogeneity to manage complexity is accelerating.

And that is the challenge that hardware and software developers face in the age of mainstream highly parallel processing. Before diving into that, I will take a diversion into the trends driving increasing (software-exposed) parallelism in hardware.

 

how hardware is changing

The oft-cited Moore’s Law has been remarkably accurate at predicting the macro trends in transistor scaling on silicon manufacturing processes for the past four decades. In a nutshell, transistor densities double every two years, indirectly to a doubling of performance for the same power budget. For the most part, this performance improvement was manifested for sin-gle-threaded applications running on microprocessors. In this era, new features in microprocessors were evaluated by how effectively they used area in return for performance.

However, in the last five years or so, semiconductor manufacturers ran into a power wall, which was essentially a slowing of the power-scaling trend. In another nutshell, whereas power density per area of silicon was roughly flat from generation to generation, power was increasing somewhat. There are several physical reasons for this (some discussed in Borkar1), but one manifestation was a slowing of voltage scaling trends (factoring in frequency, power is effectively cubic in voltage). So, in this era, new performance-ori-ented features in microprocessors are largely evaluated by how they use the power budget for performance.

Examples of power-efficient performance features are simpler cores that increase IPC (instructions per cycle), utilize less power-intensive techniques for latency hiding like simultaneous multithreading (rather than deeper, more speculative execution), wider execution payload per instruction (as in vector instructions, like Intel’s Streaming SIMD Extensions or SSE), and more cores per die. (To be sure, microprocessor vendors are adding features that enable many other important features, like improved manageability, virtual-

Calendar
of Events

september 15–18
MobileHCi ’09: 11th
international Conference on
Human Computer interaction
with Mobile devices
and services,
Bonn, germany,
Contact: reinhard oppermann,
Email: reinhard.oppermann@
fit.fraunhofer.de

september 16–18
aCM symposium on document
Engineering,
Munich, germany,
Contact: Uwe M. Borghoff,
Email: [e-mail]

september 21–22
international Conference on
automotive User interfaces
and interactive Vehicular
applications,
Essen, germany,
Contact: albrecht schmidt,
Email: albrecht.schmidt.2006@
gmail.com

september 21–23
performance Metrics for
intelligent systems,
gaithersburg, Md,
Contact: Elena r Messina,
Email: [e-mail]

september 25–26
2009 information security
Curriculum development
Conference,
Kennesaw, ga,
Contact: Michael whitman,
Email: mwhitman@kennesaw.
edu

september 30–october 2
aCM symposium on applied
perception in graphics and
Visualization,
Chania, Crete,
Contact: Katerina Mania,
Email: [e-mail]

september 30–october 2
Mindtrek 2009,
tampere Finland,
Contact: artur r. Lugmayr,
Email: [e-mail]

september 30–october 2 European Conference on Cognitive Ergonomics, Helsinki, Finland, Contact: Leena norros, Email: [e-mail]