...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
Please submit an issue on the GitHub issue tracker at https://github.com/boostorg/compute/issues.
The mailing list at https://groups.google.com/forum/#!forum/boost-compute.
Any device which implements the OpenCL standard is supported. This includes GPUs from NVIDIA, AMD, and Intel as well as CPUs from AMD and Intel and other accelerator cards such as the Xeon Phi.
Thrust implements a C++ STL-like API for GPUs and CPUs. It is built with multiple backends. NVIDIA GPUs use the CUDA backend and multi-core CPUs can use the Intel TBB or OpenMP backends. However, thrust will not work with AMD graphics cards or other lesser-known accelerators. I feel Boost.Compute is superior in that it uses the vendor-neutral OpenCL library to achieve portability across all types of compute devices.
Bolt is an AMD specific C++ wrapper around the OpenCL API which extends the C99-based OpenCL language to support C++ features (most notably templates). It is similar to NVIDIA's Thrust library and shares the same failure, lack of portability.
VexCL is an expression-template based linear-algebra library for OpenCL. The aims and scope are a bit different from the Boost Compute library. VexCL is closer in nature to the Eigen library while Boost.Compute is closer to the C++ standard library. I don't feel that Boost.Compute really fills the same role as VexCL. In fact, the recent versions of VexCL allow to use Boost.Compute as one of the backends, which makes the interaction between the two libraries a breeze.
Also see this StackOverflow question: http://stackoverflow.com/questions/20154179/differences-between-vexcl-thrust-and-boost-compute
It would not be possible to provide the same API that Thrust expects for OpenCL. The fundamental reason is that functions/functors passed to Thrust algorithms are actual compiled C++ functions whereas for Boost.Compute these form expression objects which are then translated into C99 code which is then compiled for OpenCL.
CUDA and OpenCL are two very different technologies. OpenCL works by compiling C99 code at run-time to generate kernel objects which can then be executed on the GPU. CUDA, on the other hand, works by compiling its kernels using a special compiler (nvcc) which then produces binaries which can executed on the GPU.
OpenCL already has multiple implementations which allow it to be used on a variety of platforms (e.g. NVIDIA GPUs, Intel CPUs, etc.). I feel that adding another abstraction level within Boost.Compute would only complicate and bloat the library.
Unfortunately no. OpenCL relies on having C99 source code available at run-time in order to execute code on the GPU. Thus compiled C++ functions or C++11 lambdas cannot simply be passed to the OpenCL environment to be executed on the GPU.
This is the reason why I wrote the Boost.Compute lambda library. Basically it takes C++ lambda expressions (e.g. _1 * sqrt(_1) + 4) and transforms them into C99 source code fragments (e.g. “input[i] * sqrt(input[i]) + 4)”) which are then passed to the Boost.Compute STL-style algorithms for execution. While not perfect, it allows the user to write code closer to C++ that still can be executed through OpenCL.
Also check out the BOOST_COMPUTE_FUNCTION() macro which allows OpenCL functions to be defined inline with C++ code. An example can be found in the monte_carlo example code.
Command queues specify the context and device for the algorithm's execution. For all of the standard algorithms the command_queue parameter is optional. If not provided, a default command_queue will be created for the default GPU device and the algorithm will be executed there.
This can be accompilshed easily using the generic boost::compute::copy() algorithm along with std::ostream_iterator<T>. For example:
std::cout << "vector: [ "; boost::compute::copy( vector.begin(), vector.end(), std::ostream_iterator<int>(std::cout, ", "), queue ); std::cout << "]" << std::endl;
Zero-copy memory allows OpenCL kernels to directly operate on regions of host memory (if supported by the platform).
Boost.Compute supports zero-copy memory in multiple ways. The low-level interface
is provided by allocating
objects with the
flag. The high-level interface is provided by the
class which provides a std::vector-like interface to a region of host-memory
and can be used directly with all of the Boost.Compute algorithms.
The low-level Boost.Compute APIs offer the same thread-safety guarantees as the underyling OpenCL library implementation. However, the high-level APIs make use of a few global static objects for features such as automatic program caching which makes them not thread-safe by default.
To compile Boost.Compute in thread-safe mode define
before including any of the Boost.Compute headers. By default this will require
linking your application/library with the Boost.Thread library.
Boost.Compute is used by a number of open-source libraries and applications including:
If you use Boost.Compute in your project and would like it to be listed here please send an email to Kyle Lutz (email@example.com).
We are actively seeking additional C++ developers with experience in GPGPU and parallel-computing.
Please send an email to Kyle Lutz (firstname.lastname@example.org) for more information.
Also see the contributor guide and check out the list of issues at: https://github.com/boostorg/compute/issues.