The portDNN neural network acceleration library

Table of Contents

• Supported Platforms
• Getting Started with portDNN
• Support
• Cross-compilation with ComputeCpp
• Contributions
• Citation

portDNN is a library implementing various neural network algorithms such as pooling and convolution written using SYCL and C++.

portDNN currently supports the following operations:

• 2D convolutions
• 2D depthwise convolutions
• 2D max & average pooling
• Relu and tanh activations

The convolution operations have several implementations, including tiled and Winograd kernels. The supported data format is NHWC.

The project is maintained by Codeplay Software.

Supported Platforms

The master branch of portDNN is regularly tested with the "Supported" hardware listed on the ComputeCpp Supported Platforms page. portDNN may also work on other hardware and platforms assuming they implement SPIR or SPIR-V support. portDNN is primarily tested on Ubuntu 16.04 LTS with the corresponding default package versions. portDNN will generally match the most recently released ComputeCpp, though it is likely to be compatible with other versions. We test against the most recent version.

Getting Started with portDNN

Pre-requisites

• CMake (version 3.5.1 and above)
• OpenCL 1.2-capable hardware and drivers with SPIR 1.2 or SPIR-V support
• OpenCL ICD Loader
• OpenCL headers
• gcc (version 5.4 and above)
• ComputeCpp
• Building documentation requires Doxygen and Graphviz/Dot. Tested against versions 1.8.11 and 2.38.0 respectively.

Building portDNN

portDNN uses CMake as its build system. There are provisions in the CMake files for downloading portDNN's dependencies automatically, for finding other dependencies and for selecting which bits of portDNN to build. All these configuration options can be found in the main CMakeLists.txt for the project and will show up in the CMake GUI if you use it. By default, the tests and library will be built, but not the benchmarks.

It is recommended to leave the option SNN_DOWNLOAD_MISSING_DEPS set to on. This will automatically download the source libraries necessary for portDNN to build and run (such as Google Test, Google benchmark and the Eigen linear algebra library). Even if you already have these on your machine, downloading them as part of the portDNN means a more consistent configuration.

Building with ComputeCpp

You will need to provide the location of the ComputeCpp install you are using in the variable ComputeCpp_DIR. It should point to the folder where bin/, lib/ etc. are. This should be the only argument that is mandatory, everything else should be optional. The default build type is Release, though this can be overridden.

ComputeCpp with portDNN does not currently support USM. If you build with ComputeCpp you must disable USM support.

The following command shows how to compile portDNN.

# Setup build environment
mkdir build && cd build
cmake .. -DComputeCpp_DIR=/path/to/computecpp -DSNN_ENABLE_USM=OFF
# Compile portDNN
make -j$(nproc)

Building with DPC++

You will need to provide the location of the DPC++ compiler to CMake to build with DPC++.

DPC++ does support USM. USM support will be automatically built unless you disable it with -DSNN_ENABLE_USM=OFF.

mkdir build && cd build
cmake .. -DCMAKE_CXX_COMPILER=/path/to/llvm/bin/clang++ -DSNN_BUILD_BENCHMARKS=OFF -DSNN_BENCH_SYCLBLAS=OFF 
# Compile portDNN
make -j$(nproc)

Undefined reference linker errors

portDNN exposes optional features (double and half data types, NCHW data format, USM support), that can be enabled and disabled when building the library.

Attempting to use those feature in an application that links to a build of portDNN that doesn't support them may cause undefined reference error at link time. Please ensure that your build of portDNN has the required features enabled.

You can refer to OPTIONS.md for a full list of the supported CMake options.

Sample Code

The "samples" directory contains sample code for the 2D convolution and pooling operations offered by portDNN. These binaries are compiled when building portDNN using CMake.

Running the portDNN Tests

The portDNN tests are compiled when building portDNN using CMake. The following command shows how to run the tests.

# Run the tests
ctest
# If compiled with benchmark support, run just the benchmarks
ctest -C Benchmark -E test

Support

Bug reports and Issues

Bug reports are vital to provide feedback to the developers about what is going wrong with the project, you can raise these using the "Issues" feature in GitHub.

Please make sure that your bug report contains the following information:

• A clear and descriptive title.
• The output of clinfo | grep -E "Platform ID|Name|Vendor|[Vv]ersion|Profile|Extensions".
• The output of computecpp_info.
• The exact steps and commands to run to reproduce the bug.
• The exact error text shown (if applicable), otherwise the behaviour you expected and what you encountered instead.
• Should the problem arise outside the project's test suite then please provide a minimal test to allow us to reproduce the problem.

Cross-compilation with ComputeCpp

portDNN supports cross-compilation targeting a number of devices. However, because of the two-step compilation process used in ComputeCpp, standard CMake toolchain files won't provide enough information to portDNN's build scripts to work properly.

To that end, two toolchains are available. The first, gcc-generic.cmake, will likely work with any prebuilt GCC toolchain (it is not compatible with those installed through package managers). The second is designed to work with the poky toolchain available as part of the Yocto Linux system.

The first step is to download ComputeCpp for both the host machine you are running on and for the platform you would like to target. You should make sure to match the ComputeCpp version for both downloads. Both are required so that the host can run the compiler binary, while the tools can link using the target device library. Similarly, acquire a GCC toolchain for the platform you are targeting. Lastly you should download the OpenCL headers. They are standard across all platforms, but you cannot specify the default package-managed location of /usr/include for them, as that will cause conflicts with other system headers. An easy fix is to download the headers from GitHub.

Toolchain files cannot make use cache variables set by the user when running CMake, as the cache does not exist when the toolchain is executed. Environment variables are available to toolchain files, however, so they are used to pass information to the toolchain. The gcc-generic.cmake toolchain relies on the following environment variables:

SNN_TARGET_TRIPLE # the triple of the platform you are targeting
SNN_TOOLCHAIN_DIR # The root directory of the GCC you downloaded
SNN_SYSROOT_DIR   # The system root, probably (but not necessarily)
                  # ${SNN_TOOLCHAIN_DIR}/${SNN_TARGET_TRIPLE}/libc

CMake can then be invoked in a build directory as follows:

cmake -DComputeCpp_DIR=/path/to/computecpp \
      -DComputeCpp_HOST_DIR=/path/to/host/computecpp \
      -DOpenCL_INCLUDE_DIR=/path/to/opencl/headers \
      `# For cross-compiling, check documentation for your platform` \
      -DCOMPUTECPP_BITCODE=[(spir[32|64]|spirv[32|64]|ptx64)] \
      -DSNN_BUILD_DOCUMENTATION=OFF \
      `# Next options let you install the tests to a zippable folder` \
      -DSNN_BUILD_TESTS=ON \
      -DSNN_BUILD_BENCHMARKS=ON \
      -DSNN_INSTALL_TESTS=ON \
      -DSNN_INSTALL_BENCHMARKS=ON \
      `# This is the most important part - tells CMake to crosscompile` \
      -DCMAKE_TOOLCHAIN_FILE=$PWD/../cmake/toolchains/(gcc-generic|arm-gcc-poky).cmake \
      -DCMAKE_INSTALL_PREFIX=packaged-binaries \
      -GNinja ../

The process for the poky toolchain is similar, save that you only need to provide the SNN_SYSROOT_DIR environment variable. It should be set to point to the directory named sysroots in the poky toolchain. You will likely want COMPUTECPP_BITCODE=spir32. Otherwise, these instructions should still work.

Contributions

Please see the file CONTRIBUTING.md for further details if you would like to contribute code, build systems, bug fixes or similar.

Citation

If you use portDNN in your research, please cite the library as follows:

Rod Burns, John Lawson, Duncan McBain, and Daniel Soutar. 2019. Accelerated Neural Networks on OpenCL Devices Using portDNN. In Proceedings of the International Workshop on OpenCL (IWOCL'19). ACM, New York, NY, USA, Article 10, 4 pages. DOI: https://doi.org/10.1145/3318170.3318183

@inproceedings{Burns:2019:ANN:3318170.3318183,
 author = {Burns, Rod and Lawson, John and McBain, Duncan and Soutar, Daniel},
 title = {Accelerated Neural Networks on OpenCL Devices Using portDNN},
 booktitle = {Proceedings of the International Workshop on OpenCL},
 series = {IWOCL'19},
 year = {2019},
 isbn = {978-1-4503-6230-6},
 location = {Boston, MA, USA},
 pages = {10:1--10:4},
 articleno = {10},
 numpages = {4},
 url = {http://doi.acm.org/10.1145/3318170.3318183},
 doi = {10.1145/3318170.3318183},
 acmid = {3318183},
 publisher = {ACM},
 address = {New York, NY, USA},
 keywords = {GPGPU, OpenCL, SYCL, machine learning, neural networks},
}