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An API to provide an efficient distributed queue on a cluster. Libcircle is currently used in production to quickly traverse and perform operations on a file tree which contains several hundred-million file nodes.


libcircle is an API for distributing embarrassingly parallel workloads using self-stabilization. Details on the algorithms used may be found at


Compile and install

The current build status is: Build Status

make all check
sudo make install

To enable output from libcircle (including fatal errors), run configure with "--enable-loglevel=number" where "number" is one of the following options:

  • "1" fatal errors only.
  • "2" errors and lower log levels.
  • "3" warnings and lower log levels.
  • "4" info messages on internal operations and lower log levels.
  • "5" fine grained debug messages and lower log levels.

RPM Build and Install

To build an RPM, use the following instructions:

  1. rpmbuild -ta libcircle-<version>.tar.gz
  2. rpm --install <the appropriate RPM files>

Developer API Information

The basic program flow when using libcircle is the following:

  1. Define callbacks which enqueue or dequeue strings from the queue.
  2. Execute the program.
#include <libcircle.h>

/* An example of a create callback defined by your program */
void my_create_some_work(CIRCLE_handle *handle)
     * This is where you should generate work that needs to be processed.
     * For example, if your goal is to lstat files on a large filesystem,
     * this is where you would readdir() and and enqueue directory names.
     * This should be a small amount of work. For example, only enqueue the
     * filenames from a single directory.
    while((data_to_process = readdir(...)) != NULL)

/* An example of a process callback defined by your program. */
void my_process_some_work(CIRCLE_handle *handle)
     * This is where work should be processed. For example, this is where you
     * should lstat one of the files which was placed on the queue by your
     * create_some_work callback. Again, you should try to keep this short and
     * block as little as possible.
    finished_work = lstat(my_data, ...);

 * Initialize state required by libcircle. Arguments should be those passed in
 * by the launching process. argc is a pointer to the number of arguments,
 * argv is the argument vector. The return value is the MPI rank of the current
 * process.
int rank = CIRCLE_init(&argc, argv);

 * Processing and creating work is done through callbacks. Here's how we tell
 * libcircle about our function which creates the initial work. For MPI nerds,
 * this is your rank 0 process.

 * After you give libcircle a way to create work, you need to tell it how that
 * work should be processed.

 * Now that everything is setup, lets execute everything.

 * Finally, give libcircle a chance to clean up after itself.
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