Thrust

HIP back-end for Thrust (alpha release).

Introduction

Thrust is a parallel algorithm library. This library has been ported to HIP/ROCm platform, which uses the rocPRIM library. The HIP ported library works on HIP/ROCm platforms. Currently there is no CUDA backend in place.

Requirements

Software

• Git
• CMake (3.5.1 or later)
• AMD ROCm platform (1.8.0 or later)
  • Including HipCC compiler, which must be set as C++ compiler on ROCm platform.
• rocPRIM library
  • It will be automatically downloaded and built by CMake script.

Optional:

• GTest
  • Required only for tests. Building tests is enabled by default.
  • It will be automatically downloaded and built by CMake script.

Hardware

Visit the following link for ROCm hardware requirements: https://github.com/RadeonOpenCompute/ROCm/blob/master/README.md#supported-cpus

Build And Install

git clone https://github.com/ROCmSoftwarePlatform/rocThrust

# Go to rocThrust directory, create and go to the build directory.
cd rocThrust; mkdir build; cd build

# Configure rocThrust, setup options for your system.
# Build options:
#   DISABLE_WERROR   - ON  by default, This flag disable the -Werror compiler flag
#   BUILD_TEST       - OFF by default,
#   BUILD_EXAMPLES   - OFF by default,
#   BUILD_BENCHMARKS - OFF by default,
#   DOWNLOAD_ROCPRIM - OFF by default, when ON rocPRIM will be downloaded to the build folder,
#   RNG_SEED_COUNT   - 0 by default, controls non-repeatable random dataset count
#   PRNG_SEEDS       - 1 by default, reproducible seeds to generate random data
#
# ! IMPORTANT !
# On ROCm platform set C++ compiler to HipCC. You can do it by adding 'CXX=<path-to-hipcc>'
# before 'cmake' or setting cmake option 'CMAKE_CXX_COMPILER' with the path to the HipCC compiler.
#
[CXX=hipcc] cmake ../. # or cmake-gui ../.

# Build
make -j4

# Optionally, run tests if they're enabled.
ctest --output-on-failure

# Package
make package

# Install
[sudo] make install

Macro options

# Performance improvement option. If you define THRUST_HIP_PRINTF_ENABLED before
# thrust includes to 0, you can disable printfs on device side and improve
# performance. The default value is 1
#define THRUST_HIP_PRINTF_ENABLED 0

Using rocThrust In A Project

Recommended way of including rocThrust into a CMake project is by using its package configuration files.

# On ROCm rocThrust requires rocPRIM
find_package(rocprim REQUIRED CONFIG PATHS "/opt/rocm/rocprim")

# "/opt/rocm" - default install prefix
find_package(rocthrust REQUIRED CONFIG PATHS "/opt/rocm/rocthrust")

...
includes rocThrust headers and roc::rocprim_hip target
target_link_libraries(<your_target> roc::rocthrust)

Running Unit Tests

# Go to rocThrust build directory
cd rocThrust; cd build

# Configure with examples flag on
CXX=hipcc cmake -DBUILD_TEST=ON ..

# Build tests
make -j4

# To run all tests
ctest

# To run unit tests for rocThrust
./test/<unit-test-name>

Using multiple GPUs concurrently for testing

This feature requires CMake 3.16+ to be used for building / testing. (Prior versions of CMake cannot assign ids to tests when running in parallel. Assigning tests to distinct devices could only be done at the cost of extreme complexity.)

The unit tests can make use of CTest Resource Allocation feature enabling distributing tests across multiple GPUs in an intelligent manner. The feature can accelerate testing when multiple GPUs of the same family are in a system as well as test multiple family of products from one invocation without having to resort to HIP_VISIBLE_DEVICES environment variable. The feature relies on the presence of a resource spec file.

IMPORTANT: trying to use RESOURCE_GROUPS and --resource-spec-file with CMake/CTest respectively of versions prior to 3.16 omits the feature silently. No warnings issued about unknown properties or command-line arguments. Make sure that cmake/ctest invoked are sufficiently recent.

Auto resource spec generation

There is a utility script in the repo that may be called independently:

# Go to rocThrust build directory
cd rocThrust; cd build

# Invoke directly or use CMake script mode via cmake -P
../cmake/GenerateResourceSpec.cmake

# Assuming you have 2 compatible GPUs in the system
ctest --resource-spec-file ./resources.json --parallel 2

Manual

Assuming the user has 2 GPUs from the gfx900 family and they are the first devices enumerated by the system one may specify during configuration -D AMDGPU_TEST_TARGETS=gfx900 stating only one family will be tested. Leaving this var empty (default) results in targeting the default device in the system. To let CMake know there are 2 GPUs that should be targeted, one has to feed CTest a JSON file via the --resource-spec-file <path_to_file> flag. For example:

{
  "version": {
    "major": 1,
    "minor": 0
  },
  "local": [
    {
      "gfx900": [
        {
          "id": "0"
        },
        {
          "id": "1"
        }
      ]
    }
  ]
}

Using custom seeds for the tests

There are 2 CMake configuration-time options that control random data fed to unit tests.

• RNG_SEED_COUNT, (0 by default) controls non-repeatable random dataset count. It draws values from a default constructed std::random_device. Should tests fail, the actual seed producing the failure are reported by Gtest, enabling reproducibility.
• PRNG_SEEDS, (1 by default) controls repeatable dataset seeds. It is a CMake formatted (semi-colon delimited) array of 32-bit unsigned integrals.
  • (Note: semi-colons often collide with shell command parsing. It is advised to escape the entire CMake CLI argument to avoid the variable itself picking up quotation marks. Pass cmake "-DPRNG_SEEDS=1;2;3;4" instead of cmake -DPRNG_SEEDS="1;2;3;4", the two cases differ in how the CMake executable receives its arguments from the OS.)

Running Examples

# Go to rocThrust build directory
cd rocThrust; cd build

# Configure with examples flag on
CXX=hipcc cmake -DBUILD_EXAMPLES=ON ..

# Build examples
make -j4

# Run the example you want to run
# ./examples/example_thrust_<example-name>
# For example:
./examples/example_thrust_version

# Example for linking with cpp files
./examples/cpp_integration/example_thrust_linking

Running Benchmarks

# Go to rocThrust build directory
cd rocThrust; cd build

# Configure with benchmarks flag on
CXX=hipcc cmake -DBUILD_BENCHMARKS=ON ..

# Build benchmarks
make -j4

# Run the benchmarks
./benchmarks/benchmark_thrust_bench

Documentation

Documentation is available here.

Support

Bugs and feature requests can be reported through the issue tracker.

Contributions and License

Contributions of any kind are most welcome! More details are found at CONTRIBUTING and LICENSE.