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SUMMARY:A Simple and Efficient Memory Model for Concurrent Programming Lan
 guages - Todd Millstein (UCLA)
DTSTART:20101019T120000Z
DTEND:20101019T130000Z
UID:TALK26945@talks.cam.ac.uk
CONTACT:Thomas Tuerk
DESCRIPTION:The most intuitive memory model for shared-memory multithreade
 d programming is sequential consistency (SC)\, but it disallows the use of
  many compiler and hardware optimizations thereby impacting performance. D
 ata-race-free (DRF) models\, such as the proposed C++0x\nmemory model\, gu
 arantee SC execution for data-race-free programs. But these models provide
  no guarantee at all for racy programs\, compromising the safety and debug
 gability of such programs. To address the safety issue\, the Java memory m
 odel\, which is also based on the\nDRF model\, provides a weak semantics f
 or racy executions. However\, this semantics is subtle and complex\, makin
 g it difficult for programmers to reason about their programs and for comp
 iler writers to ensure the correctness of compiler optimizations.\n\nWe pr
 esent the DRFx memory model\, which is simple for programmers to understan
 d and use while still supporting many common optimizations. We introduce a
  memory model (MM) exception which can be signaled to halt execution. If a
  program executes without throwing this exception\, then DRFx guarantees t
 hat the execution is SC. If a program throws an MM exception during an exe
 cution\, then DRFx guarantees that the program has a data race. We observe
  that SC violations can be detected in hardware through a lightweight form
  of conflict detection. Furthermore\, our model safely allows aggressive c
 ompiler and hardware optimizations within compiler-designated program regi
 ons.\n\nIn ongoing work we are simplifying the required hardware support a
 nd exploring techniques to automatically recover from MM exceptions.\n\nJo
 int work with Dan Marino (UCLA)\, Abhayendra Singh and Satish Narayanasamy
  (University of Michigan\, Ann Arbor)\, and Madan Musuvathi (Microsoft Res
 earch Redmond).\n
LOCATION:Computer Laboratory\, William Gates Building\, Room SS03
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