Getting Started
Celerity is a high-level C++17 API and runtime environment that aims to bring the power and ease of use of SYCL to distributed-memory accelerator clusters.
If you want to get your hands dirty right away, move on to the Installation guide.
Transparently Scale Your Applications
Celerity allows you to write highly parallel applications that can be run on a cluster of accelerator nodes. It focuses on providing a way of scaling applications to many nodes without having to be an expert in cluster programming. In fact, the Celerity API does not make it apparent that a program is (potentially) running on many nodes at all: There is no notion of ranks; partitioning of work and data is taken care of transparently behind the scenes. This lets you focus on your actual work, without having to concern yourself with the complexities of modern distributed memory cluster programming.
A Word of Caution
While ease of use is one of Celerity's main goals, simplicity can only go so far without sacrificing considerable performance. Proficiency in modern C++ as well as at least a rough understanding of how accelerator (GPU) programming differs from parallel CPU programming is required to make efficient use of Celerity. Additionally, you will require a good understanding of the algorithms and techniques you intend to implement using Celerity in order for the runtime system to be able to run it on a cluster both correctly and in an efficient manner.
Built on a Strong Foundation
Celerity is built on top of SYCL, an open-standard high-level C++ embedded domain specific language for programming accelerators. SYCL provides a great API that hits a sweet spot between expressiveness and power as well as ease of use, making it the perfect starting point for Celerity: We set out to find the minimal set of API extensions required to bring the SYCL API to distributed memory clusters - thus making it relatively easy to migrate an existing SYCL application to Celerity. If you don't have any experience with SYCL, don't worry, as we will introduce the most important concepts along the way.
Points of Divergence
While it is one of Celerity's Core Principles to stick as closely to SYCL as possible, the Celerity API is neither a super- nor subset of the SYCL API: On one hand certain SYCL features, such as SYCL 2020's unified shared memory (USM), are inherently unsuitable for distributed memory execution and can therefore not be supported by Celerity. On the other hand, certain high-performance computing (HPC) features such as Collective Host Tasks are required to make Celerity work at scale.
Starting with Celerity 0.3.0, most supported SYCL features are made available through the
celerity::namespace, in addition to thesycl::namespace. When in doubt, we recommend sticking to the former.
Further Reading
If this piqued your interest and you would like to try it for yourself, check out the Installation section on how to build and install Celerity. For a complete example of how to set up a Celerity application from start to finish, see the Tutorial.
For more information on the overall Celerity API as well as the driving principles behind its design, please see our Celerity in-depth Overview section.