The Java Memory Model

The Java memory model, as described in chapter 17 of the Java Language Specification defines how threads interact through memory. It used to be somewhat unclear and unnecessarily limiting, but some folks decided this was a bad idea and revised it. I was one of those people.

Brian Goetz and I wrote something of a gentle introduction to some of the issues. It may help you to understand the implications of this work.

This page mostly details my contributions to the work. For more of an introduction to the material, click here .

Relevant Publications

The Java Memory Model. Jeremy Manson, William Pugh and Sarita Adve. A journal version that combines my thesis, the POPL paper and the CSJP paper. For academics, this is probably the most interesting version of the paper. pdf .
The Java Memory Model. Jeremy Manson, William Pugh and Sarita Adve. In Proceedings of the 32nd ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages, POPL 2005. Long Beach, California. January, 2005. pdf .
The Java Memory Model. Jeremy Manson. Ph.D. Dissertation. September, 2004. pdf .
Requirements for a Programming Language Memory Model. Jeremy Manson and William Pugh. Workshop on Concurrency and Synchronization in Java Programs, in association with PODC. July, 2004. pdf .
Manson, Jeremy. The Design and Verification of Java's Memory Model. In OOPSLA 2002 Doctoral Symposium. postscript , PDF .
Manson, Jeremy and Pugh, William. The Java Memory Model Simulator. In Workshop on Formal Techniques for Java-like Programs, in association with ECOOP. June, 2002. PostScript version, PDF version.
Manson, Jeremy and Pugh, William. Semantics of Multithreaded Java. Department of Computer Science, University of Maryland, College Park, CS-TR-4215. compressed postscript , ordinary postscript
Manson, Jeremy. Virtual Machine Implementation Issues for the Revised Java Memory Model. University of Maryland, December 2001. M.S. Thesis. PDF
Manson, Jeremy and Pugh, William. Core Semantics of Multithreaded Java. In ACM Java Grande . June, 2001. See "Semantics of Multithreaded Java" above instead.

Talk Slides

In June 2005, I gave a talk at IBM. Those slides are here.
In June 2004, Bill Pugh and I gave a talk at a large, well-attended Java conference. The slides are here.
We also gave an invited talk about the memory model at Dagstuhl in 2003. The slides are available here.
We also gave a semi-invited talk about the memory model at 2002's ECOOP Workshop on Formal Techniques for Java-like Programs in combination with the simulator paper (above). The slides are available on line: PDF, ppt.

The Java Memory Model Simulator

I have written a simulator for the model. I am fairly well aware that there are bugs in it. I know of at least one example on which it produces incomplete results. If you have questions, or you have suggestions on how it can be improved, or you find errors (especially if you find errors!) email me at jmanson@nospamcs.umd.edu . But take out the "nospam" part first. David Hovemeyer did a good chunk of the work as well.

The Documentation

We presented a paper on the simulator at 2002's ECOOP Workshop on Formal Techniques for Java-like Programs . PostScript version, PDF version. It has changed substantially since then; there is more information about how it works in my dissertation (above).
To understand the simulator, you really need the readme. The readme dates from the earlier version, so the information on the back end has changed (and users can ignore the information about prescient writes / initWrites), but the information on how to get it to work is more-or-less current. PostScript version, PDF version .
A set of litmus tests for the simulator are available. tar.gz format .

The Java Version

The simulator is available in executable JAR format .
So are the sources . Requires Generics for Java, as per JSR 14.

The Haskell Version

I wrote a version of the 2002 simulator in Java. It doesn't implement the correct model, so it is only really here out of curiosity.

The simulator for Windows in zip format (this requires an unzip program, like Winzip, pkzip or the builtin one in Windows XP). Tested on NT 4.
The simulator for Solaris in tar.gz format . Tested on Solaris 2.6.
The simulator for Linux in tar.gz format . Tested on RedHat 7.2.
The source code for the simulator in tar.gz format . The simulator is written in a mix of Haskell and Java. Compilation requires a Java compiler, a reasonable make utility, and The Glasgow Haskell Compiler .

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