Download Cilk

The latest version of the Cilk system consists of the Tapir/LLVM compiler and the Cheetah runtime library. This version has been tested on x86-64 systems running recent distributions of Linux: Ubuntu 18.04 and 20.04, FreeBSD 13, Fedora 32, and Mac OS X 10.15 and 11.2

There are binary releases for two common systems (Linux/Ubuntu 18 and Mac OS) at OpenCilk Binary Releases

A docker image is now available as well.

If you want to build from source, our welcome message and build instructions are here: OpenCilk README + Build Instructions

The Tapir/LLVM compiler is the newest compiler that supports Cilk. Tapir/LLVM extends LLVM and Clang with support for the Cilk keywords, Cilk reducer hyperobjects, and a version of the grainsize pragma for cilk_for loops. The Tapir/LLVM compiler implements the Tapir extension of LLVM’s intermediate representation (Schardl et al., 2017) to compile task-parallel programs more efficiently than previous compilers. Tapir/LLVM also includes the Cilksan determinacy-race detector, which is guaranteed to find a race if one exists or certify the absence of races in a program execution.

The current release of the Tapir/LLVM compiler is based on version 10.0 of LLVM and Clang.


  1. Schardl, T. B., Moses, W. S., & Leiserson, C. E. (2017). Tapir: Embedding Fork-Join Parallelism into LLVM’s Intermediate Representation. PPoPP, 249–265.

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