A COMMENT ONMANY-CORE COMPUTINGAND REAL-TIME AUDIO SOFTWARE
SYSTEMS (2008)
Ge WangCenter for Computer Research in Music and Acoustics
(CCRMA)
Stanford [email protected]
While much remains to be seen in the ongoing shift to-wards
massively many-core computing, one perhaps piv-otal point of focus
lies at the intersection of low-level im-plementation languages
(e.g., C/C++) and runtime oper-ating system support. Here, we
briefly discuss one issuein this area: concurrent programming
models and whatmay need to happen to languages and operating
systemsto effectively support audio programming on many-coresystems
such that existing and future audio softwarescan take advantage of
these systems.
The up-to-now dominant model of using preemptivethreading to
distribute computation among multiple coresis rapidly becoming less
solvent for time-critical, high-throughput systems, such as
real-time audio engines (themodel was never ideal from a
programming point of view,and many-core computing further
accentuates its short-comings). Due to their nondeterministic
nature, preemp-tive threads are inherently difficult to reason
about, debug,and maintain. Also, the preemptive nature and
computa-tional overhead of threads make it hard to synchronize
par-allel computations in predictable and time-sensitive
ways.Furthermore, it is often unclear (to programmers)
whetherparallelization via threads are beneficial to a
particularsituation the decision depends on many complex
factorssuch as the nature of the algorithm, timing and
synchro-nization needs, as well as the number of available cores-
too few threads will fail to take advantage, too manythreads can
introduce significant overhead due to unneces-sary thread
management, context-switching, and schedul-ing. This can make it
extremely challenging to re-architectexisting, sequential systems
for many-core.
Adopting a developer-centric point of view, it seemsimperative
that the computing community should producean agreed-upon,
generalized lower-level concurrent pro-gramming paradigm (e.g.,
language extensions at the C/C++level, plus integrated OS support)
that can flexibly specifysynchronous, multi-core friendly programs.
Such a pro-gramming model should allow concurrent code to
operateand synchronize with minimal overhead, while
leveragingunderlying operating system support to abstract the
under-lying core configuration/availability.
One potentially promising approach lies in Apples up-coming 10.6
(Snow Leopard) release of the OS X oper-ating system [1], which is
to offer both the addition ofblocks (parallelizable segments of
code) as an under-
lying programming language feature, along with a cen-tralized
mechanism in the operating system kernel, calledGrand Central
Dispatch (GCD). In short, GCD interpretsthe blocks specified by the
programmer in real-time, andallocates them across available cores
(and potentially theGPU). This approach eliminates the need for
program-mers to account for exactly how many cores are
present,while reducing thread-allocation overheads by centraliz-ing
blocks and dynamically deciding when to spawn newparallel entities
as beneficial. Also importantly, this ap-proach seems to be
potentially scalable. Of course, it re-mains to be seen how this
approach actually works, in par-ticular with a wide array of audio
systems. At the sametime, it is encouraging that a major OS
platform has takenconcrete, developer-centric steps to try and
address themany-core problem.
Hopefully other platforms (e.g., Linux and Windows)will follow
suit, and the community can produce a portable,industry-wide
many-core programming standard. As de-signers and implementors of
real-time computer music soft-ware, it is crucial for us to
experiment early and freelywith technology as they become
available, and to cham-pion audio-friendly solutions at every
level.
1. REFERENCES
[1] Apple Inc. 2008. Mac OS X State of theUnion, Keynote, Apple
World Wide Devel-oper Conference.
IndexICMC 2008 HomeConference InfoWelcome from the ICMA
PresidentICMA OfficersWelcome from the ICMC 2008 Organising
CommitteeICMC 2008Previous ICMCsICMC 2008 Paper Panel & Music
CuratorsICMC 2008 ReviewersICMC 2008 Best Paper Award
SessionsMonday, 25 August 2008Languages and Environments
1Interaction and Improvisation 1Sound SynthesisComputational
Modeling of MusicDemos 1Posters 1Interaction and Improvisation
2Aesthetics, History, and Philosophy 1
Tuesday, 26 August 2008MiscellaneousAlgorithmic Composition
Tools 1Network PerformanceComputational Music Analysis 1Panel 1:
Reinventing Audio and Music Computation fo ...Panel 2: Towards an
Interchange Format for Spatial ...
Wednesday, 27 August 2008Studio Reports 1Mobile Computer
Ensemble PlayDemos 2Posters 2Algorithmic Composition Tools
2Interface, Gesture, and Control 1
Thursday, 28 August 2008Interface, Gesture, and Control
2Languages and Environments 2Spatialization 1Computational Music
Analysis 2Panel 3: Network PerformanceDemos 3Posters 3
Friday, 29 August 2008Sound ProcessingAesthetics, History, and
Philosophy 2Interface, Gesture, and Control 3Spatialization
2Algorithmic Composition Tools 3Studio Reports 2
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Topicscritical theory/philosophy of technology, postmodern cy
...sociology/anthropology of everyday sounds, situated per
...history of computer music, women and gender studies, ed
...philosophy/culture/psychology, music information retrie
...electroacoustic music composition, aesthetics of music,
...singing analysis/synthesis, music analysis/synthesis, v
...interactive and real-time systems and languages, music
...human-computer interaction, sound synthesis/analysis, i
...interaction design, computer music, performance art, el
...physical interface design, performance systems, gesture
...language/education/history/sociology of computer music,
...composition systems and techniques, languages for compu
...programming languages/systems, audio synthesis/analysis
...composition, music cognition, music informatics, human- ...music
information retrieval, audio signal processing, p ...computational
musicology, music cognition, music and AI ...music cognition,
rhythm/meter/timing/tempo, computation ...music information
retrieval, audio content analysis, to ...spatial audio, audio
signal processing, auditory percep ...physical modelling, spatial
audio, room acoustics, aura ...sonic interaction design,
physics-based sound synthesis ...audio signal processing, sound
synthesis, acoustics of ...audio signal processing, acoustics,
software systemsphysics-based sound synthesis, virtual room
acousticscomposition, music analysis, software for pedagogyPANEL:
Towards an Interchange Format for Spatial audio ...PANEL: Network
PerformancePANEL: Reinventing Audio and Music Computation for Many
...
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