Habanero-C Library (HClib)

What is HClib?¶

Habanero C/C++ library (HClib) is a lightweight asynchronous many-task (AMT) programming model-based runtime. It uses a lightweight work-stealing scheduler to schedule the tasks. HClib uses a persistent thread pool called workers, on which tasks are scheduled and load balanced using lock-free concurrent deques. HClib exposes several programming constructs to the user, which in turn helps them to express parallelism easily and efficiently.

A brief summary of the relevant APIs is as follows:

launch: Used for creating an HClib context.
async: Used for creating asynchronous tasks dynamically.
finish: Used for bulk task synchronization. It waits on all tasks spawned (including nested tasks) within the scope of the finish.
promise and future: Used for point-to-point inter-task synchronization in C++11. A promise is a single-assignment thread-safe container, that is used to write some value and a future is a read-only handle for its value. Waiting on a future causes a task to suspend until the corresponding promise is satisfied by putting some value to the promise.

An example HClib program¶

The following example creates an HClib context in which there is a finish scope that waits on a task created by async. Since the task assign 1 to ran, after the finish scope, the value of ran should be 1.

#include <stdlib.h>
#include <stdio.h>
#include <assert.h>

#include "hclib_cpp.h"

int ran = 0;

int main (int argc, char ** argv) {
    const char *deps[] = { "system" };
    hclib::launch(deps, 1, []() {
        hclib::finish([]() {
            printf("Hello\n");
            hclib::async([&](){ ran = 1; });
        });
    });
    assert(ran == 1);
    printf("Exiting...\n");
    return 0;
}

Habanero-C Library (HClib)

What is HClib?¶

An example HClib program¶

Further Readings¶