Chapel GPU Documentation

Overview

This document describes the following two Chapel modules that facilitate GPU programming in Chapel:

  • GPUIterator: A Chapel iterator that facilitates invoking user-written GPU programs (e.g., CUDA/HIP/OpenCL) from Chapel programs. It is also designed to easily perform hybrid and/or distributed execution - i.e., CPU-only, GPU-only, X% for CPU + Y% for GPU on a single or multiple CPU+GPU node(s), which helps the user to explore the best configuration.

  • GPUAPI: Chapel-level GPU API that allows the user to perform basic operations such as GPU memory (de)allocations, device-to-host/host-to-device transfers, and so on. This module can be used either standalone or with the GPUIterator module. Currently, the following two tiers of API are provided:

    • MID-level: Provides Chapel user-friendly GPU API functions.

      • Example: var ga = new GPUArray(A);
    • MID-LOW-level: Provides wrapper functions for raw GPU API functions

      • Example: var ga: c_void_ptr = Malloc(sizeInBytes);

Also, in this document, for categorization purposes, the term LOW-level is referred to a GPUIterator only version, where the GPUIterator is only used for invoking raw GPU programs in which there is no Chapel-level abstraction.