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Five Outstanding Additions Found in SYCL 2020

In this article, James Brodman and John Pennycook review five outstanding additions found in SYCL 2020. A key goal of SYCL 2020 is to align SYCL with ISO C++, which has two benefits. First, it ensures that SYCL feels natural to C++ programmers. Second, it allows SYCL to act as a proving ground for multivendor, multiarchitecture solutions to heterogeneous programming that may inform other C++ libraries (and perhaps ISO C++ itself).

Many of the syntactic changes in SYCL 2020 are a result of updating the base language from C++11 to C++17, enabling developers to take advantage of features such as class template argument deduction (CTAD) and deduction guides. But there are many new features, too! In this article, we choose to highlight five features new in SYCL 2020 and talk a little about why they matter.

  • Backends open the door for SYCL implementations built on other languages/frameworks besides OpenCL, enabling SYCL to target a wider variety of hardware.
  • Unified shared memory (USM) is a pointer-based access model, which serves as an alternative to the buffer/accessor model from SYCL 1.2.1.
  • Reductions are a common programming pattern, which SYCL 2020 accelerates via a “built-in” library.
  • The group library provides abstractions for cooperative work items, yielding additional application performance and programmer productivity through alignment with underlying hardware capabilities (regardless of vendor).
  • Atomic references aligned with the C++20 std::atomic_ref extend the C++ memory model to heterogeneous devices.