Citation
Edward A. Lee. "The Problem with Threads". Technical report, EECS Dept., University of California, Berkeley, 1, 2006.

Abstract
Threads are a seemingly straightforward adaptation of the dominant sequential model of computation to concurrent systems. Languages require little or no syntactic changes to support threads, and operating systems and architectures have evolved to efficiently support them. Many technologists are pushing for increased use of multithreading in software in order to take advantage of the predicted increases in parallelism in computer architectures. In this paper, I argue that this is not a good idea. Although threads seem to be a small step from sequential computation, in fact, they represent a huge step. They discard the most essential and appealing properties of sequential computation: understandability, predictability, and determinism. Threads, as a model of computation, are wildly nondeterministic, and the job of the programmer becomes one of pruning that nondeterminism. Although many research techniques improve the model by offering more effective pruning, I argue that this is approaching the problem backwards. Rather than pruning nondeterminism, we should build from essentially deterministic, composable components. Nondeterminism should be explicitly and judiciously introduced where needed, rather than removed where not needed. The consequences of this principle are profound. I argue for the development of concurrent coordination languages based on sound, composable formalisms. I believe that such languages will yield much more reliable, and more concurrent programs.

Electronic downloads

• http://www.eecs.berkeley.edu/Pubs/TechRpts/2006/EECS-2006-1.html

• HTML

  Edward A. Lee. <a
  href="http://chess.eecs.berkeley.edu/pubs/53.html"
  ><i>The Problem with Threads</i></a>,
  Technical report,  EECS Dept., University of California,
  Berkeley, 1, 2006.

• Plain text

  Edward A. Lee. "The Problem with Threads".
  Technical report,  EECS Dept., University of California,
  Berkeley, 1, 2006.

• BibTeX

  @techreport{Lee06_ProblemWithThreads,
      author = {Edward A. Lee},
      title = {The Problem with Threads},
      institution = {EECS Dept., University of California, Berkeley},
      number = {1},
      year = {2006},
      abstract = {Threads are a seemingly straightforward adaptation
                of the dominant sequential model of computation to
                concurrent systems. Languages require little or no
                syntactic changes to support threads, and
                operating systems and architectures have evolved
                to efficiently support them. Many technologists
                are pushing for increased use of multithreading in
                software in order to take advantage of the
                predicted increases in parallelism in computer
                architectures. In this paper, I argue that this is
                not a good idea. Although threads seem to be a
                small step from sequential computation, in fact,
                they represent a huge step. They discard the most
                essential and appealing properties of sequential
                computation: understandability, predictability,
                and determinism. Threads, as a model of
                computation, are wildly nondeterministic, and the
                job of the programmer becomes one of pruning that
                nondeterminism. Although many research techniques
                improve the model by offering more effective
                pruning, I argue that this is approaching the
                problem backwards. Rather than pruning
                nondeterminism, we should build from essentially
                deterministic, composable components.
                Nondeterminism should be explicitly and
                judiciously introduced where needed, rather than
                removed where not needed. The consequences of this
                principle are profound. I argue for the
                development of concurrent coordination languages
                based on sound, composable formalisms. I believe
                that such languages will yield much more reliable,
                and more concurrent programs.},
      URL = {http://chess.eecs.berkeley.edu/pubs/53.html}
  }
  

Posted by Mary Stewart on 4 May 2006.
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