The Java memory model is fatally flawed

@article{Pugh2000TheJM,
  title={The Java memory model is fatally flawed},
  author={William W. Pugh},
  journal={Concurr. Pract. Exp.},
  year={2000},
  volume={12},
  pages={445-455}
}
  • W. Pugh
  • Published 1 May 2000
  • Computer Science
  • Concurr. Pract. Exp.
The Java memory model described in Chapter 17 of the Java Language Specification gives constraints on how threads interact through memory. This chapter is hard to interpret and poorly understood; it imposes constraints that prohibit common compiler optimizations and are expensive to implement on existing hardware. Most JVMs violate the constraints of the existing Java memory model; conforming to the existing specification would impose significant performance penalties. In addition… 
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References

SHOWING 1-10 OF 12 REFERENCES

Java consistency: nonoperational characterizations for Java memory behavior

This work provides a simpler definition of consistency model for Java, in which it is clearly distinguish the consistency model that is promised to the programmer from that which should be implemented in the JVM, and precisely defines their discrepancy.

From Sequential to Multi-Threaded Java: An Event-Based Operational Semantics

Event spaces are included in the operational judgements to develop the semantics of the full multi-threaded sublanguage of Java, which is shown to extend the one for sequential Java conservatively, allowing sequential programs to be reasoned about in a simplified computational framework without loss of generality.

The power of processor consistency

This work uses a formal model to give two distinct definitions of processors consistency: one corresponding to Goodman’s original proposal and the other corresponding that given by the implementors of the DASH system.

The Java Language Specification

The Java Language Specification, Second Edition is the definitive technical reference for the Java programming language and provides complete, accurate, and detailed coverage of the syntax and semantics of the Java language.

Formal Syntax and Semantics of Java

  • J. Alves-Foss
  • Computer Science
    Lecture Notes in Computer Science
  • 2002
This paper describes the Semantics of Java and proposes a Programmer Friendly Modular Definition of the Sem semantics of Java, as well as investigating the role of semantics in programming.

Java in practice : design styles and idioms for effective Java

This chapter discusses type safety and constants, as well as diagrams and coding conventions, and the design principles and tips used in the development of types for knowledge representation.

Detecting equality of variables in programs

An algorithm for detecting when two computations produce equivalent values by developing a static property called congruence, which is conservative in that any variables detected to be e:quivalent will in fact be equivalent, but not all equivalences are detected.

Global value numbers and redundant computations

This work proposes a redundancy elimination algorithm that is global (in that it deals with the entire program), yet able to recognize redundancy among expressions that are lexitally different, and takes advantage of second order effects.

Impact of ”reads kill” in java

  • http://www.cs.umd.edu/ ∼pugh/ java/readsKillImpact.html, May
  • 1999

Impact of " reads kill " in java

  • Impact of " reads kill " in java
  • 1999