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OpenCL (Open Computing Language) is a
framework A framework is a generic term commonly referring to an essential supporting structure which other things are built on top of. Framework may refer to: Computing * Application framework, used to implement the structure of an application for an op ...
for writing programs that execute across
heterogeneous Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...
platforms consisting of
central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
s (CPUs),
graphics processing unit A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, m ...
s (GPUs),
digital signal processor A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on MOS integrated circuit chips. They are widely used in audio s ...
s (DSPs),
field-programmable gate array A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term ''Field-programmability, field-programmable''. The FPGA configuration is generally specifi ...
s (FPGAs) and other processors or
hardware accelerator Hardware acceleration is the use of computer hardware designed to perform specific functions more efficiently when compared to software running on a general-purpose central processing unit (CPU). Any transformation of data that can be calcul ...
s. OpenCL specifies
programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...
s (based on C99, C++14 and
C++17 C17, C-17 or C.17 may refer to: Transportation * , a 1917 British C-class submarine Air * Boeing C-17 Globemaster III, a military transport aircraft * Lockheed Y1C-17 Vega, a six-passenger monoplane * Cierva C.17, a 1928 English experimental ...
) for programming these devices and
application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...
s (APIs) to control the platform and execute programs on the compute devices. OpenCL provides a standard interface for
parallel computing Parallel computing is a type of computation in which many calculations or processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. There are several different f ...
using task- and data-based parallelism. OpenCL is an open standard maintained by the
non-profit A nonprofit organization (NPO) or non-profit organisation, also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, public or social benefit, in co ...
technology consortium Khronos Group. Conformant implementations are available from
Altera Altera Corporation was a manufacturer of programmable logic devices (PLDs) headquartered in San Jose, California. It was founded in 1983 and acquired by Intel in 2015. The main product lines from Altera were the flagship Stratix series, mid-ran ...
, AMD, ARM,
Creative Creative may refer to: *Creativity, phenomenon whereby something new and valuable is created * "Creative" (song), a 2008 song by Leon Jackson * Creative class, a proposed socioeconomic class * Creative destruction, an economic term * Creative dir ...
, IBM,
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,
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...
,
Nvidia Nvidia CorporationOfficially written as NVIDIA and stylized in its logo as VIDIA with the lowercase "n" the same height as the uppercase "VIDIA"; formerly stylized as VIDIA with a large italicized lowercase "n" on products from the mid 1990s to ...
,
Qualcomm Qualcomm () is an American multinational corporation headquartered in San Diego, California, and incorporated in Delaware. It creates semiconductors, software, and services related to wireless technology. It owns patents critical to the 5G, ...
,
Samsung The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
, Vivante,
Xilinx Xilinx, Inc. ( ) was an American technology and semiconductor company that primarily supplied programmable logic devices. The company was known for inventing the first commercially viable field-programmable gate array (FPGA) and creating the fi ...
, and
ZiiLABS ZiiLABS is a global electronics company, producing a line of media-oriented application processors, reference platforms and enabling software, in a series of platforms named ZMS. Its products are found in low-power consumer electronics and embedded ...
.


Overview

OpenCL views a computing system as consisting of a number of ''compute devices'', which might be
central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
s (CPUs) or "accelerators" such as graphics processing units (GPUs), attached to a ''host'' processor (a CPU). It defines a C-like language for writing programs. Functions executed on an OpenCL device are called " kernels". A single compute device typically consists of several ''compute units'', which in turn comprise multiple ''
processing element This glossary of computer hardware terms is a list of definitions of terms and concepts related to computer hardware, i.e. the physical and structural components of computers, architectural issues, and peripheral devices. A ...
s'' (PEs). A single kernel execution can run on all or many of the PEs in parallel. How a compute device is subdivided into compute units and PEs is up to the vendor; a compute unit can be thought of as a " core", but the notion of core is hard to define across all the types of devices supported by OpenCL (or even within the category of "CPUs"), and the number of compute units may not correspond to the number of cores claimed in vendors' marketing literature (which may actually be counting
SIMD lanes Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it should ...
). In addition to its C-like programming language, OpenCL defines an
application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...
(API) that allows programs running on the host to launch kernels on the compute devices and manage device memory, which is (at least conceptually) separate from host memory. Programs in the OpenCL language are intended to be compiled at run-time, so that OpenCL-using applications are portable between implementations for various host devices. The OpenCL standard defines host APIs for C and C++; third-party APIs exist for other programming languages and platforms such as Python,
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
,
Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offic ...
, D and .NET. An
implementation Implementation is the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy. Industry-specific definitions Computer science In computer science, an implementation is a real ...
of the OpenCL standard consists of a
library A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vi ...
that implements the API for C and C++, and an OpenCL C
compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs tha ...
for the compute device(s) targeted. In order to open the OpenCL programming model to other languages or to protect the kernel source from inspection, the Standard Portable Intermediate Representation (SPIR) can be used as a target-independent way to ship kernels between a front-end compiler and the OpenCL back-end. More recently Khronos Group has ratified SYCL, a higher-level programming model for OpenCL as a single-source
eDSL A domain-specific language (DSL) is a computer language specialized to a particular application Domain (software engineering), domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains. There are a ...
based on pure
C++17 C17, C-17 or C.17 may refer to: Transportation * , a 1917 British C-class submarine Air * Boeing C-17 Globemaster III, a military transport aircraft * Lockheed Y1C-17 Vega, a six-passenger monoplane * Cierva C.17, a 1928 English experimental ...
to improve programming productivity. People interested by C++ kernels but not by SYCL single-source programming style can use C++ features with compute kernel sources written in "C++ for OpenCL" language.


Memory hierarchy

OpenCL defines a four-level
memory hierarchy In computer architecture, the memory hierarchy separates computer storage into a hierarchy based on response time. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and controll ...
for the compute device: * global memory: shared by all processing elements, but has high access latency (); * read-only memory: smaller, low latency, writable by the host CPU but not the compute devices (); * local memory: shared by a group of processing elements (); * per-element private memory ( registers; ). Not every device needs to implement each level of this hierarchy in hardware.
Consistency In classical deductive logic, a consistent theory is one that does not lead to a logical contradiction. The lack of contradiction can be defined in either semantic or syntactic terms. The semantic definition states that a theory is consistent ...
between the various levels in the hierarchy is relaxed, and only enforced by explicit
synchronization Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...
constructs, notably barriers. Devices may or may not share memory with the host CPU. The host API provides handles on device memory buffers and functions to transfer data back and forth between host and devices.


OpenCL kernel language

The programming language that is used to write
compute kernel In computing, a compute kernel is a routine compiled for high throughput accelerators (such as graphics processing units (GPUs), digital signal processors (DSPs) or field-programmable gate arrays (FPGAs)), separate from but used by a main pro ...
s is called kernel language. OpenCL adopts C/ C++-based languages to specify the kernel computations performed on the device with some restrictions and additions to facilitate efficient mapping to the heterogeneous hardware resources of accelerators. Traditionally OpenCL C was used to program the accelerators in OpenCL standard, later C++ for OpenCL kernel language was developed that inherited all functionality from OpenCL C but allowed to use C++ features in the kernel sources.


OpenCL C language

OpenCL C is a C99-based language dialect adapted to fit the device model in OpenCL. Memory buffers reside in specific levels of the
memory hierarchy In computer architecture, the memory hierarchy separates computer storage into a hierarchy based on response time. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and controll ...
, and pointers are annotated with the region qualifiers , , , and , reflecting this. Instead of a device program having a function, OpenCL C functions are marked to signal that they are
entry point In computer programming Computer programming is the process of performing a particular computation (or more generally, accomplishing a specific computing result), usually by designing and building an executable computer program. Programmin ...
s into the program to be called from the host program.
Function pointer A function pointer, also called a subroutine pointer or procedure pointer, is a pointer that points to a function. As opposed to referencing a data value, a function pointer points to executable code within memory. Dereferencing the function poi ...
s, bit fields and variable-length arrays are omitted, and
recursion Recursion (adjective: ''recursive'') occurs when a thing is defined in terms of itself or of its type. Recursion is used in a variety of disciplines ranging from linguistics to logic. The most common application of recursion is in mathematic ...
is forbidden. The
C standard library The C standard library or libc is the standard library for the C programming language, as specified in the ISO C standard. ISO/IEC (2018). '' ISO/IEC 9899:2018(E): Programming Languages - C §7'' Starting from the original ANSI C standard, it was ...
is replaced by a custom set of standard functions, geared toward math programming. OpenCL C is extended to facilitate use of parallelism with vector types and operations, synchronization, and functions to work with work-items and work-groups. In particular, besides scalar types such as and , which behave similarly to the corresponding types in C, OpenCL provides fixed-length vector types such as (4-vector of single-precision floats); such vector types are available in lengths two, three, four, eight and sixteen for various base types. Vectorized operations on these types are intended to map onto
SIMD Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it shoul ...
instructions sets, e.g., SSE or VMX, when running OpenCL programs on CPUs. Other specialized types include 2-d and 3-d image types.


Example: matrix–vector multiplication

The following is a matrix–vector multiplication algorithm in OpenCL C. // Multiplies A*x, leaving the result in y. // A is a row-major matrix, meaning the (i,j) element is at A *ncols+j __kernel void matvec(__global const float *A, __global const float *x, uint ncols, __global float *y) The kernel function computes, in each invocation, the
dot product In mathematics, the dot product or scalar productThe term ''scalar product'' means literally "product with a scalar as a result". It is also used sometimes for other symmetric bilinear forms, for example in a pseudo-Euclidean space. is an alg ...
of a single row of a matrix and a vector : :y_i = a_ \cdot x = \sum_j a_ x_j. To extend this into a full matrix–vector multiplication, the OpenCL runtime
maps A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes. Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although ...
the kernel over the rows of the matrix. On the host side, the function does this; it takes as arguments the kernel to execute, its arguments, and a number of work-items, corresponding to the number of rows in the matrix .


Example: computing the FFT

This example will load a
fast Fourier transform A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). Fourier analysis converts a signal from its original domain (often time or space) to a representation in ...
(FFT) implementation and execute it. The implementation is shown below. The code asks the OpenCL library for the first available graphics card, creates memory buffers for reading and writing (from the perspective of the graphics card), JIT-compiles the FFT-kernel and then finally asynchronously runs the kernel. The result from the transform is not read in this example. #include #include #include "CL/opencl.h" #define NUM_ENTRIES 1024 int main() // (int argc, const char* argv[]) The actual calculation inside file "fft1D_1024_kernel_src.cl" (based o
Fitting FFT onto the G80 Architecture
: R"( // This kernel computes FFT of length 1024. The 1024 length FFT is decomposed into // calls to a radix 16 function, another radix 16 function and then a radix 4 function __kernel void fft1D_1024 (__global float2 *in, __global float2 *out, __local float *sMemx, __local float *sMemy) )" A full, open source implementation of an OpenCL FFT can be found on Apple's website.


C++ for OpenCL language

In 2020, Khronos announced the transition to the community driven C++ for OpenCL programming language that provides features from
C++17 C17, C-17 or C.17 may refer to: Transportation * , a 1917 British C-class submarine Air * Boeing C-17 Globemaster III, a military transport aircraft * Lockheed Y1C-17 Vega, a six-passenger monoplane * Cierva C.17, a 1928 English experimental ...
in combination with the traditional OpenCL C features. This language allows to leverage a rich variety of language features from standard C++ while preserving backward compatibility to OpenCL C. This opens up a smooth transition path to C++ functionality for the OpenCL kernel code developers as they can continue using familiar programming flow and even tools as well as leverage existing extensions and libraries available for OpenCL C. The language semantics is described in the documentation published in the releases of OpenCL-Docs repository hosted by the Khronos Group but it is currently not ratified by the Khronos Group. The C++ for OpenCL language is not documented in a stand-alone document and it is based on the specification of C++ and OpenCL C. The open source Clang compiler has supported C++ for OpenCL since release 9. C++ for OpenCL has been originally developed as a Clang compiler extension and appeared in the release 9. As it was tightly coupled with OpenCL C and did not contain any Clang specific functionality its documentation has been re-hosted to the OpenCL-Docs repository from the Khronos Group along with the sources of other specifications and reference cards. The first official release of this document describing C++ for OpenCL version 1.0 has been published in December 2020. C++ for OpenCL 1.0 contains features from C++17 and it is backward compatible with OpenCL C 2.0. In December 2021 a new provisional C++ for OpenCL version 2021 has been released which is fully compatible with the OpenCL 3.0 standard. A work in progress draft of the latest C++ for OpenCL documentation can be found on the Khronos website.


Features

C++ for OpenCL supports most of the features (syntactically and semantically) from OpenCL C except for nested parallelism and blocks. However, there are minor differences in some supported features mainly related to differences in semantics between C++ and C. For example, C++ is more strict with the implicit type conversions and it does not support the type qualifier. The following C++ features are not supported by C++ for OpenCL: virtual functions, operator, non-placement / operators, exceptions, pointer to member functions, references to functions, C++ standard libraries. C++ for OpenCL extends the concept of separate memory regions (''address spaces'') from OpenCL C to C++ features - functional casts, templates, class members, references, lambda functions,  operators. Most of C++ features are not available for the kernel functions e.g. overloading or templating, arbitrary class layout in parameter type.


Example: complex-number arithmetic

The following code snippet illustrates how kernels with complex-number arithmetic can be implemented in C++ for OpenCL language with convenient use of C++ features. // Define a class Complex, that can perform complex-number computations with // various precision when different types for T are used - double, float, half. template class complex_t ; // A helper function to compute multiplication over complex numbers read from // the input buffer and to store the computed result into the output buffer. template void compute_helper(__global T *in, __global T *out) // This kernel is used for complex-number multiplication in single precision. __kernel void compute_sp(__global float *in, __global float *out) #ifdef cl_khr_fp16 // This kernel is used for complex-number multiplication in half precision when // it is supported by the device. #pragma OPENCL EXTENSION cl_khr_fp16: enable __kernel void compute_hp(__global half *in, __global half *out) #endif


Tooling and Execution Environment

C++ for OpenCL language can be used for the same applications or libraries and in the same way as OpenCL C language is used. Due to the rich variety of C++ language features, applications written in C++ for OpenCL can express complex functionality more conveniently than applications written in OpenCL C and in particular generic programming paradigm from C++ is very attractive to the library developers. C++ for OpenCL sources can be compiled by OpenCL drivers that support ''cl_ext_cxx_for_opencl'' extension. Arm has announced support for this extension in December 2020. However, due to increasing complexity of the algorithms accelerated on OpenCL devices, it is expected that more applications will compile C++ for OpenCL kernels offline using stand alone compilers such as Clang into executable binary format or portable binary format e.g. SPIR-V. Such an executable can be loaded during the OpenCL applications execution using a dedicated OpenCL API. Binaries compiled from sources in C++ for OpenCL 1.0 can be executed on OpenCL 2.0 conformant devices. Depending on the language features used in such kernel sources it can also be executed on devices supporting earlier OpenCL versions or OpenCL 3.0. Aside from OpenCL drivers kernels written in C++ for OpenCL can be compiled for execution on Vulkan devices using clspv compiler and clvk runtime layer just the same way as OpenCL C kernels.


Contributions

C++ for OpenCL is an open language developed by the community of contributors listed in its documentation.  New contributions to the language semantic definition or open source tooling support are accepted from anyone interested as soon as they are aligned with the main design philosophy and they are reviewed and approved by the experienced contributors.


History

OpenCL was initially developed by Apple Inc., which holds
trademark A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from ot ...
rights, and refined into an initial proposal in collaboration with technical teams at AMD, IBM,
Qualcomm Qualcomm () is an American multinational corporation headquartered in San Diego, California, and incorporated in Delaware. It creates semiconductors, software, and services related to wireless technology. It owns patents critical to the 5G, ...
,
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...
, and
Nvidia Nvidia CorporationOfficially written as NVIDIA and stylized in its logo as VIDIA with the lowercase "n" the same height as the uppercase "VIDIA"; formerly stylized as VIDIA with a large italicized lowercase "n" on products from the mid 1990s to ...
. Apple submitted this initial proposal to the Khronos Group. On June 16, 2008, the Khronos Compute Working Group was formed with representatives from CPU, GPU, embedded-processor, and software companies. This group worked for five months to finish the technical details of the specification for OpenCL 1.0 by November 18, 2008. This technical specification was reviewed by the Khronos members and approved for public release on December 8, 2008.


OpenCL 1.0

OpenCL 1.0 released with Mac OS X Snow Leopard on August 28, 2009. According to an Apple press release:
Snow Leopard further extends support for modern hardware with Open Computing Language (OpenCL), which lets any application tap into the vast gigaflops of GPU computing power previously available only to graphics applications. OpenCL is based on the C programming language and has been proposed as an open standard.
AMD decided to support OpenCL instead of the now deprecated
Close to Metal In computing, Close To Metal ("CTM" in short, originally called ''Close-to-the-Metal'') is the name of a beta version of a low-level programming interface developed by ATI, now the AMD Graphics Product Group, aimed at enabling GPGPU computing. CTM ...
in its Stream framework. RapidMind announced their adoption of OpenCL underneath their development platform to support GPUs from multiple vendors with one interface. On December 9, 2008, Nvidia announced its intention to add full support for the OpenCL 1.0 specification to its GPU Computing Toolkit. On October 30, 2009, IBM released its first OpenCL implementation as a part of the XL compilers. Acceleration of calculations with factor to 1000 are possible with OpenCL in graphic cards against normal CPU. Some important features of next Version of OpenCL are optional in 1.0 like double- or half-precision operations.


OpenCL 1.1

OpenCL 1.1 was ratified by the Khronos Group on June 14, 2010 and adds significant functionality for enhanced parallel programming flexibility, functionality, and performance including: * New data types including 3-component vectors and additional image formats; * Handling commands from multiple host threads and processing buffers across multiple devices; * Operations on regions of a buffer including read, write and copy of 1D, 2D, or 3D rectangular regions; * Enhanced use of events to drive and control command execution; * Additional OpenCL built-in C functions such as integer clamp, shuffle, and asynchronous strided copies; * Improved OpenGL interoperability through efficient sharing of images and buffers by linking OpenCL and OpenGL events.


OpenCL 1.2

On November 15, 2011, the Khronos Group announced the OpenCL 1.2 specification, which added significant functionality over the previous versions in terms of performance and features for parallel programming. Most notable features include: * Device partitioning: the ability to partition a device into sub-devices so that work assignments can be allocated to individual compute units. This is useful for reserving areas of the device to reduce latency for time-critical tasks. * Separate compilation and linking of objects: the functionality to compile OpenCL into external libraries for inclusion into other programs. * Enhanced image support (optional): 1.2 adds support for 1D images and 1D/2D image arrays. Furthermore, the OpenGL sharing extensions now allow for OpenGL 1D textures and 1D/2D texture arrays to be used to create OpenCL images. * Built-in kernels: custom devices that contain specific unique functionality are now integrated more closely into the OpenCL framework. Kernels can be called to use specialised or non-programmable aspects of underlying hardware. Examples include video encoding/decoding and digital signal processors. * DirectX functionality: DX9 media surface sharing allows for efficient sharing between OpenCL and DX9 or
DXVA DirectX Video Acceleration (DXVA) is a Microsoft API specification for the Microsoft Windows and Xbox 360 platforms that allows video decoding to be hardware-accelerated. The pipeline allows certain CPU-intensive operations such as iDCT, mo ...
media surfaces. Equally, for DX11, seamless sharing between OpenCL and DX11 surfaces is enabled. * The ability to force
IEEE 754 The IEEE Standard for Floating-Point Arithmetic (IEEE 754) is a technical standard for floating-point arithmetic established in 1985 by the Institute of Electrical and Electronics Engineers (IEEE). The standard addressed many problems found ...
compliance for single-precision floating-point math: OpenCL by default allows the single-precision versions of the division, reciprocal, and square root operation to be less accurate than the correctly rounded values that IEEE 754 requires. If the programmer passes the "-cl-fp32-correctly-rounded-divide-sqrt" command line argument to the compiler, these three operations will be computed to IEEE 754 requirements if the OpenCL implementation supports this, and will fail to compile if the OpenCL implementation does not support computing these operations to their correctly-rounded values as defined by the IEEE 754 specification. This ability is supplemented by the ability to query the OpenCL implementation to determine if it can perform these operations to IEEE 754 accuracy.


OpenCL 2.0

On November 18, 2013, the Khronos Group announced the ratification and public release of the finalized OpenCL 2.0 specification. Updates and additions to OpenCL 2.0 include: * Shared virtual memory * Nested parallelism * Generic address space * Images (optional, include 3D-Image) * C11 atomics * Pipes * Android installable client driver extension * half precision extended with optional cl_khr_fp16 extension * cl_double: double precision IEEE 754 (optional)


OpenCL 2.1

The ratification and release of the OpenCL 2.1 provisional specification was announced on March 3, 2015 at the Game Developer Conference in San Francisco. It was released on November 16, 2015. It introduced the OpenCL C++ kernel language, based on a subset of C++14, while maintaining support for the preexisting OpenCL C kernel language. Vulkan and OpenCL 2.1 share
SPIR-V Standard Portable Intermediate Representation (SPIR) is an intermediate language for parallel compute and graphics by Khronos Group. It is used in multiple execution environments, including the Vulkan graphics API and the OpenCL compute API, to re ...
as an
intermediate representation An intermediate representation (IR) is the data structure or code used internally by a compiler or virtual machine to represent source code. An IR is designed to be conducive to further processing, such as optimization and translation. A "good" ...
allowing high-level language front-ends to share a common compilation target. Updates to the OpenCL API include: * Additional subgroup functionality * Copying of kernel objects and states * Low-latency device timer queries * Ingestion of SPIR-V code by runtime * Execution priority hints for queues * Zero-sized dispatches from host AMD, ARM, Intel, HPC, and YetiWare have declared support for OpenCL 2.1.


OpenCL 2.2

OpenCL 2.2 brings the OpenCL C++ kernel language into the core specification for significantly enhanced parallel programming productivity. It was released on May 16, 2017. Maintenance Update released in May 2018 with bugfixes. * The OpenCL C++ kernel language is a static subset of the C++14 standard and includes classes, templates, lambda expressions, function overloads and many other constructs for generic and meta-programming. * Uses the new Khronos
SPIR-V Standard Portable Intermediate Representation (SPIR) is an intermediate language for parallel compute and graphics by Khronos Group. It is used in multiple execution environments, including the Vulkan graphics API and the OpenCL compute API, to re ...
1.1 intermediate language which fully supports the OpenCL C++ kernel language. * OpenCL library functions can now use the C++ language to provide increased safety and reduced undefined behavior while accessing features such as atomics, iterators, images, samplers, pipes, and device queue built-in types and address spaces. * Pipe storage is a new device-side type in OpenCL 2.2 that is useful for FPGA implementations by making connectivity size and type known at compile time, enabling efficient device-scope communication between kernels. * OpenCL 2.2 also includes features for enhanced optimization of generated code: applications can provide the value of specialization constant at SPIR-V compilation time, a new query can detect non-trivial constructors and destructors of program scope global objects, and user callbacks can be set at program release time. * Runs on any OpenCL 2.0-capable hardware (only a driver update is required).


OpenCL 3.0

The OpenCL 3.0 specification was released on September 30, 2020 after being in preview since April 2020. OpenCL 1.2 functionality has become a mandatory baseline, while all OpenCL 2.x and OpenCL 3.0 features were made optional. The specification retains the OpenCL C language and deprecates the OpenCL C++ Kernel Language, replacing it with the C++ for OpenCL language based on a Clang/
LLVM LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate repre ...
compiler which implements a subset of
C++17 C17, C-17 or C.17 may refer to: Transportation * , a 1917 British C-class submarine Air * Boeing C-17 Globemaster III, a military transport aircraft * Lockheed Y1C-17 Vega, a six-passenger monoplane * Cierva C.17, a 1928 English experimental ...
and
SPIR-V Standard Portable Intermediate Representation (SPIR) is an intermediate language for parallel compute and graphics by Khronos Group. It is used in multiple execution environments, including the Vulkan graphics API and the OpenCL compute API, to re ...
intermediate code. Version 3.0.7 of C++ for OpenCL with some Khronos openCL extensions were presented at IWOCL 21. Actual is 3.0.11 with some new extensions and corrections. NVIDIA, working closely with the Khronos OpenCL Working Group, improved Vulkan Interop with semaphores and memory sharing.


Roadmap

When releasing OpenCL 2.2, the Khronos Group announced that OpenCL would converge where possible with Vulkan to enable OpenCL software deployment flexibility over both APIs. This has been now demonstrated by Adobe's Premiere Rush using the clspv open source compiler to compile significant amounts of OpenCL C kernel code to run on a Vulkan runtime for deployment on Android. OpenCL has a forward looking roadmap independent of Vulkan, with 'OpenCL Next' under development and targeting release in 2020. OpenCL Next may integrate extensions such as Vulkan / OpenCL Interop, Scratch-Pad Memory Management, Extended Subgroups, SPIR-V 1.4 ingestion and SPIR-V Extended debug info. OpenCL is also considering Vulkan-like loader and layers and a ‘Flexible Profile’ for deployment flexibility on multiple accelerator types.


Open source implementations

OpenCL consists of a set of headers and a shared object that is loaded at runtime. An installable client driver (ICD) must be installed on the platform for every class of vendor for which the runtime would need to support. That is, for example, in order to support Nvidia devices on a Linux platform, the Nvidia ICD would need to be installed such that the OpenCL runtime (the ICD loader) would be able to locate the ICD for the vendor and redirect the calls appropriately. The standard OpenCL header is used by the consumer application; calls to each function are then proxied by the OpenCL runtime to the appropriate driver using the ICD. Each vendor must implement each OpenCL call in their driver. The Apple, Nvidia,
ROCm ROCm is an Advanced Micro Devices (AMD) software stack for graphics processing unit (GPU) programming. ROCm spans several domains: general-purpose computing on graphics processing units (GPGPU), high performance computing (HPC), heterogeneous ...
, RapidMind and
Gallium3D Mesa, also called Mesa3D and The Mesa 3D Graphics Library, is an open source implementation of OpenGL, Vulkan, and other graphics API specifications. Mesa translates these specifications to vendor-specific graphics hardware drivers. Its most im ...
implementations of OpenCL are all based on the
LLVM LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate repre ...
Compiler technology and use the Clang compiler as their frontend. ; MESA Gallium Compute: An implementation of OpenCL (actual 1.1 incomplete, mostly done AMD Radeon GCN) for a number of platforms is maintained as part of the Gallium Compute Project, which builds on the work of the Mesa project to support multiple platforms. Formerly this was known as CLOVER., actual development: mostly support for running incomplete framework with actual LLVM and CLANG, some new features like fp16 in 17.3, Target complete OpenCL 1.0, 1.1 and 1.2 for AMD and Nvidia. New Basic Development is done by
Red Hat Red Hat, Inc. is an American software company that provides open source software products to enterprises. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North Carolina, with other offices worldwide. Red Hat has become a ...
with SPIR-V also for Clover. New Target is modular OpenCL 3.0 with full support of OpenCL 1.2. Actual state is available in Mesamatrix. Image supports are here in the focus of development. RustiCL is a new implementation for Gallium compute with Rust instead of C for better code. In Mesa 22.2 experimental implementation will be available with openCL 3.0-support and image extension implementation for programs like Darktable. ; BEIGNET: An implementation by Intel for its Ivy Bridge + hardware was released in 2013. This software from Intel's China Team, has attracted criticism from developers at AMD and
Red Hat Red Hat, Inc. is an American software company that provides open source software products to enterprises. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North Carolina, with other offices worldwide. Red Hat has become a ...
, as well as
Michael Larabel Phoronix Test Suite (PTS) is a free and open-source benchmark software for Linux and other operating systems which is developed by Michael Larabel and Matthew Tippett. The Phoronix Test Suite has been endorsed by sites such as Linux.com, Linu ...
of
Phoronix Phoronix Test Suite (PTS) is a free and open-source benchmark software for Linux and other operating systems which is developed by Michael Larabel and Matthew Tippett. The Phoronix Test Suite has been endorsed by sites such as Linux.com, Linu ...
. Actual Version 1.3.2 support OpenCL 1.2 complete (Ivy Bridge and higher) and OpenCL 2.0 optional for Skylake and newer. support for Android has been added to Beignet., actual development targets: only support for 1.2 and 2.0, road to OpenCL 2.1, 2.2, 3.0 is gone to NEO. ; NEO: An implementation by Intel for Gen. 8 Broadwell + Gen. 9 hardware released in 2018. This driver replaces Beignet implementation for supported platforms (not older 6.gen to Haswell). NEO provides OpenCL 2.1 support on Core platforms and OpenCL 1.2 on Atom platforms. Actual in 2020 also Graphic Gen 11 Ice Lake and Gen 12 Tiger Lake are supported. New OpenCL 3.0 is available for Alder Lake, Tiger Lake to Broadwell with Version 20.41+. It includes now optional OpenCL 2.0, 2.1 Features complete and some of 2.2. ; ROCm : Created as part of AMD's GPUOpen,
ROCm ROCm is an Advanced Micro Devices (AMD) software stack for graphics processing unit (GPU) programming. ROCm spans several domains: general-purpose computing on graphics processing units (GPGPU), high performance computing (HPC), heterogeneous ...
(Radeon Open Compute) is an open source Linux project built on OpenCL 1.2 with language support for 2.0. The system is compatible with all modern AMD CPUs and APUs (actual partly GFX 7, GFX 8 and 9), as well as Intel Gen7.5+ CPUs (only with PCI 3.0). With version 1.9 support is in some points extended experimental to Hardware with PCIe 2.0 and without atomics. An overview of actual work is done on XDC2018. ROCm Version 2.0 supports Full OpenCL 2.0, but some errors and limitations are on the todo list. Version 3.3 is improving in details. Version 3.5 does support OpenCL 2.2. Version 3.10 was with improvements and new APIs. Announced at SC20 is ROCm 4.0 with support of AMD Compute Card Instinct MI 100. Actual documentation of 5.1.1 and before is available at github. OpenCL 3.0 is available. ; POCL: A portable implementation supporting CPUs and some GPUs (via
CUDA CUDA (or Compute Unified Device Architecture) is a parallel computing platform and application programming interface (API) that allows software to use certain types of graphics processing units (GPUs) for general purpose processing, an approach ...
and HSA). Building on Clang and
LLVM LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate repre ...
. With version 1.0 OpenCL 1.2 was nearly fully implemented along with some 2.x features. Version 1.2 is with LLVM/CLANG 6.0, 7.0 and Full OpenCL 1.2 support with all closed tickets in Milestone 1.2. OpenCL 2.0 is nearly full implemented. Version 1.3 Supports Mac OS X. Version 1.4 includes support for
LLVM LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate repre ...
8.0 and 9.0. Version 1.5 implements LLVM/Clang 10 support. Version 1.6 implements LLVM/Clang 11 support and CUDA Acceleration. Actual targets are complete OpenCL 2.x, OpenCL 3.0 and improvement of performance. POCL 1.6 is with manual optimization at the same level of Intel compute runtime. Version 1.7 implements LLVM/Clang 12 support and some new OpenCL 3.0 features. Version 1.8 implements LLVM/Clang 13 support. Version 3.0 implements OpenCL 3.0 at minimum level and LLVM/Clang 14. ; Shamrock: A Port of Mesa Clover for ARM with full support of OpenCL 1.2, no actual development for 2.0. ; FreeOCL : A CPU focused implementation of OpenCL 1.2 that implements an external compiler to create a more reliable platform, no actual development. ; MOCL: An OpenCL implementation based on POCL by the NUDT researchers for Matrix-2000 was released in 2018. The Matrix-2000 architecture is designed to replace the Intel Xeon Phi accelerators of the TianHe-2 supercomputer. This programming framework is built on top of LLVM v5.0 and reuses some code pieces from POCL as well. To unlock the hardware potential, the device runtime uses a push-based task dispatching strategy and the performance of the kernel atomics is improved significantly. This framework has been deployed on the TH-2A system and is readily available to the public. Some of the software will next ported to improve POCL. ; VC4CL: An OpenCL 1.2 implementation for the VideoCore IV (BCM2763) processor used in the
Raspberry Pi Raspberry Pi () is a series of small single-board computers (SBCs) developed in the United Kingdom by the Raspberry Pi Foundation in association with Broadcom. The Raspberry Pi project originally leaned towards the promotion of teaching basic ...
before its model 4.


Vendor implementations


Timeline of vendor implementations

* June, 2008: During Apple’s WWDC conference an early beta of Mac OS X Snow Leopard was made available to the participants, it included the first beta implementation of OpenCL, about 6 months before the final version 1.0 specification was ratified late 2008. They also showed two demos. One was a grid of 8x8 screens rendered, each displaying the screen of an emulated Apple II machine — 64 independent instances in total, each running a famous karate game. This showed task parallelism, on the CPU. The other demo was a N-body simulation running on the GPU of a Mac Pro, a data parallel task. * December 10, 2008: AMD and Nvidia held the first public OpenCL demonstration, a 75-minute presentation at
SIGGRAPH SIGGRAPH (Special Interest Group on Computer Graphics and Interactive Techniques) is an annual conference on computer graphics (CG) organized by the ACM SIGGRAPH, starting in 1974. The main conference is held in North America; SIGGRAPH Asia ...
Asia 2008. AMD showed a CPU-accelerated OpenCL demo explaining the scalability of OpenCL on one or more cores while Nvidia showed a GPU-accelerated demo. * March 16, 2009: at the 4th Multicore Expo, Imagination Technologies announced the
PowerVR PowerVR is a division of Imagination Technologies (formerly VideoLogic) that develops hardware and software for 2D and 3D rendering, and for video encoding, decoding, associated image processing and DirectX, OpenGL ES, OpenVG, and OpenCL accel ...
SGX543MP, the first GPU of this company to feature OpenCL support. * March 26, 2009: at GDC 2009, AMD and Havok demonstrated the first working implementation for OpenCL accelerating Havok Cloth on AMD
Radeon HD 4000 series The Radeon R700 is the engineering codename for a graphics processing unit series developed by Advanced Micro Devices under the ATI Technologies, ATI brand name. The foundation chip, codenamed ''RV770'', was announced and demonstrated on June 16, ...
GPU. * April 20, 2009: Nvidia announced the release of its OpenCL driver and SDK to developers participating in its OpenCL Early Access Program. * August 5, 2009: AMD unveiled the first development tools for its OpenCL platform as part of its ATI Stream SDK v2.0 Beta Program. * August 28, 2009: Apple released Mac OS X Snow Leopard, which contains a full implementation of OpenCL. * September 28, 2009: Nvidia released its own OpenCL drivers and SDK implementation. * October 13, 2009: AMD released the fourth beta of the ATI Stream SDK 2.0, which provides a complete OpenCL implementation on both R700/ R800 GPUs and
SSE3 SSE3, Streaming SIMD Extensions 3, also known by its Intel code name Prescott New Instructions (PNI), is the third iteration of the SSE instruction set for the IA-32 (x86) architecture. Intel introduced SSE3 in early 2004 with the Prescott revis ...
capable CPUs. The SDK is available for both Linux and Windows. * November 26, 2009: Nvidia released drivers for OpenCL 1.0 (rev 48). * October 27, 2009: S3 released their first product supporting native OpenCL 1.0 – the Chrome 5400E embedded graphics processor. * December 10, 2009:
VIA Via or VIA may refer to the following: Science and technology * MOS Technology 6522, Versatile Interface Adapter * ''Via'' (moth), a genus of moths in the family Noctuidae * Via (electronics), a through-connection * VIA Technologies, a Taiwa ...
released their first product supporting OpenCL 1.0 – ChromotionHD 2.0 video processor included in VN1000 chipset. * December 21, 2009: AMD released the production version of the ATI Stream SDK 2.0, which provides OpenCL 1.0 support for R800 GPUs and beta support for R700 GPUs. * June 1, 2010:
ZiiLABS ZiiLABS is a global electronics company, producing a line of media-oriented application processors, reference platforms and enabling software, in a series of platforms named ZMS. Its products are found in low-power consumer electronics and embedded ...
released details of their first OpenCL implementation for the ZMS processor for handheld, embedded and digital home products. * June 30, 2010: IBM released a fully conformant version of OpenCL 1.0. * September 13, 2010:
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...
released details of their first OpenCL implementation for the Sandy Bridge chip architecture. Sandy Bridge will integrate Intel's newest graphics chip technology directly onto the central processing unit. * November 15, 2010:
Wolfram Research Wolfram Research, Inc. ( ) is an American multinational company that creates computational technology. Wolfram's flagship product is the technical computing program Wolfram Mathematica, first released on June 23, 1988. Other products include ...
released Mathematica 8 wit
OpenCLLink
package. * March 3, 2011: Khronos Group announces the formation of the
WebCL WebCL (Web Computing Language) is a JavaScript binding to OpenCL for Heterogeneous computing, heterogeneous parallel computing within any compatible web browser without the use of Plug-in (computing), plug-ins, first announced in March 2011. It is ...
working group to explore defining a
JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...
binding to OpenCL. This creates the potential to harness
GPU A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobi ...
and
multi-core CPU A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such ...
parallel processing from a
Web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used o ...
. * March 31, 2011: IBM released a fully conformant version of OpenCL 1.1. * April 25, 2011: IBM released OpenCL Common Runtime v0.1 for Linux on x86 Architecture. * May 4, 2011: Nokia Research releases an open source WebCL extension for the
Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current ...
web browser, providing a JavaScript binding to OpenCL. * July 1, 2011: Samsung Electronics releases an open source prototype implementation of WebCL for WebKit, providing a JavaScript binding to OpenCL. * August 8, 2011: AMD released the OpenCL-driven AMD Accelerated Parallel Processing (APP) Software Development Kit (SDK) v2.5, replacing the ATI Stream SDK as technology and concept. * December 12, 2011: AMD released AMD APP SDK v2.6 which contains a preview of OpenCL 1.2. * February 27, 2012:
The Portland Group PGI (formerly The Portland Group, Inc.) was a company that produced a set of commercially available Fortran, C and C++ compilers for high-performance computing systems. On July 29, 2013, Nvidia acquired The Portland Group, Inc.ARM CPUs. * April 17, 2012: Khronos released a WebCL working draft. * May 6, 2013: Altera released the Altera SDK for OpenCL, version 13.0. It is conformant to OpenCL 1.0. * November 18, 2013: Khronos announced that the specification for OpenCL 2.0 had been finalized. * March 19, 2014: Khronos releases the WebCL 1.0 specification. * August 29, 2014: Intel releases HD Graphics 5300 driver that supports OpenCL 2.0. * September 25, 2014: AMD releases Catalyst 14.41 RC1, which includes an OpenCL 2.0 driver. * January 14, 2015: Xilinx Inc. announces SDAccel development environment for OpenCL, C, and C++, achieves Khronos Conformance. * April 13, 2015: Nvidia releases WHQL driver v350.12, which includes OpenCL 1.2 support for GPUs based on Kepler or later architectures. Driver 340+ support OpenCL 1.1 for Tesla and Fermi. * August 26, 2015: AMD released AMD APP SDK v3.0 which contains full support of OpenCL 2.0 and sample coding. * November 16, 2015: Khronos announced that the specification for OpenCL 2.1 had been finalized. * April 18, 2016: Khronos announced that the specification for OpenCL 2.2 had been provisionally finalized. * November 3, 2016 Intel support for Gen7+ of OpenCL 2.1 in SDK 2016 r3. * February 17, 2017: Nvidia begins evaluation support of OpenCL 2.0 with driver 378.66. * May 16, 2017: Khronos announced that the specification for OpenCL 2.2 had been finalized with SPIR-V 1.2. * May 14, 2018: Khronos announced Maintenance Update for OpenCL 2.2 with Bugfix and unified headers. * April 27, 2020: Khronos announced provisional Version of OpenCL 3.0. * June 1, 2020: Intel Neo Runtime with OpenCL 3.0 for new Tiger Lake. * June 3, 2020: AMD announced RocM 3.5 with OpenCL 2.2 support. * September 30, 2020: Khronos announced that the specifications for OpenCL 3.0 had been finalized (CTS also available). * October 16, 2020: Intel announced with Neo 20.41 support for OpenCL 3.0 (includes mostly of optional OpenCL 2.x). * April 6, 2021: Nvidia supports OpenCL 3.0 for Ampere. Maxwell and later GPUs also supports OpenCL 3.0 with Nvidia driver 465+. * August 20, 2022: Intel Arc Alchemist GPUs (Arc A380, A350M, A370M, A550M, A730M and A770M) are conformant with OpenCL 3.0. * October 14, 2022: Arm Mali-G615 and Mali-G715 Immortalis are conformant with OpenCL 3.0. * November 11, 2022: The Rusticl OpenCL Library is conformant with OpenCL 3.0.


Devices

As of 2016, OpenCL runs on
graphics processing unit A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, m ...
s (GPUs), CPUs with
SIMD Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it shoul ...
instructions,
FPGAs A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware de ...
,
Movidius Myriad 2 Movidius is a company based in San Mateo, California, that designs specialised low-power processor chips for computer vision. The company was acquired by Intel in September 2016. Company history Movidius was co-founded in Dublin in 2005, by Sea ...
,
Adapteva Epiphany Zero ASIC Corporation, formerly Adapteva, Inc., is a fabless semiconductor company focusing on low power many core microprocessor design. The company was the second company to announce a design with 1,000 specialized processing cores on a single i ...
and DSPs.


Khronos Conformance Test Suite

:To be officially conformant, an implementation must pass the Khronos Conformance Test Suite (CTS), with results being submitted to the Khronos Adopters Program. The Khronos CTS code for all OpenCL versions has been available in open source since 2017.


Conformant products

The Khronos Group maintains an extended list of OpenCL-conformant products. All standard-conformant implementations can be queried using one of the clinfo tools (there are multiple tools with the same name and similar feature set).


Version support

Products and their version of OpenCL support include:


OpenCL 3.0 support

All hardware with OpenCL 1.2+ is possible, OpenCL 2.x only optional, Khronos Test Suite available since 2020-10 * (2020) Intel NEO Compute: 20.41+ for Gen 12 Tiger Lake to Broadwell (include full 2.0 and 2.1 support and parts of 2.2) * (2020) Intel 6th, 7th, 8th, 9th, 10th, 11th gen processors ( Skylake, Kaby Lake, Coffee Lake,
Comet Lake Comet Lake is Intel's codename for its 10th generation Core microprocessors. They are manufactured using Intel's third 14 nm Skylake process refinement, succeeding the Whiskey Lake U-series mobile processor and Coffee Lake desktop proce ...
, Ice Lake, Tiger Lake) with latest Intel Windows graphics driver * (2021) Intel 11th, 12th gen processors (
Rocket Lake Rocket Lake is Intel's codename for its 11th generation Core microprocessors. Released on March 30, 2021, it is based on the new Cypress Cove microarchitecture, a variant of Sunny Cove (used by Intel's Ice Lake mobile processors) backporte ...
, Alder Lake) with latest Intel Windows graphics driver * (2021) Arm Mali-G78, Mali-G310, Mali-G510, Mali-G610, Mali-G710 and Mali-G78AE. * (2022) Intel 13th gen processors ( Raptor Lake) with latest Intel Windows graphics driver * (2022)
Intel Arc Intel Arc is a brand of graphics processing units designed by Intel. These are discrete GPUs mostly marketed for the high-margin PC gaming market. The brand also covers Intel's consumer graphics software and services. Intel Arc is competing wi ...
discrete graphics with latest Intel Arc Windows graphics driver * (2021) Nvidia
Maxwell Maxwell may refer to: People * Maxwell (surname), including a list of people and fictional characters with the name ** James Clerk Maxwell, mathematician and physicist * Justice Maxwell (disambiguation) * Maxwell baronets, in the Baronetage of ...
,
Pascal Pascal, Pascal's or PASCAL may refer to: People and fictional characters * Pascal (given name), including a list of people with the name * Pascal (surname), including a list of people and fictional characters with the name ** Blaise Pascal, Frenc ...
, Volta, Turing and
Ampere The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...
with Nvidia graphics driver 465+. * (2022) Nvidia
Ada Lovelace Augusta Ada King, Countess of Lovelace (''née'' Byron; 10 December 1815 – 27 November 1852) was an English mathematician and writer, chiefly known for her work on Charles Babbage's proposed mechanical general-purpose computer, the An ...
with Nvidia graphics driver 525+. * (2022) Samsung Xclipse 920 GPU (based on AMD RDNA2)


OpenCL 2.2 support

''None yet'': Khronos Test Suite ready, with Driver Update all Hardware with 2.0 and 2.1 support possible * Intel NEO Compute: Work in Progress for actual products * ROCm: Version 3.5+ mostly


OpenCL 2.1 support

* (2018+) Support backported to Intel 5th and 6th gen processors ( Broadwell, Skylake) * (2017+) Intel 7th, 8th, 9th, 10th gen processors ( Kaby Lake, Coffee Lake,
Comet Lake Comet Lake is Intel's codename for its 10th generation Core microprocessors. They are manufactured using Intel's third 14 nm Skylake process refinement, succeeding the Whiskey Lake U-series mobile processor and Coffee Lake desktop proce ...
, Ice Lake) * Khronos: with Driver Update all Hardware with 2.0 support possible


OpenCL 2.0 support

* (2011+) AMD GCN GPU's (HD 7700+/HD 8000/Rx 200/Rx 300/Rx 400/Rx 500/Rx 5000-Series), some GCN 1st Gen only 1.2 with some Extensions * (2013+) AMD GCN APU's (
Jaguar The jaguar (''Panthera onca'') is a large cat species and the only living member of the genus ''Panthera'' native to the Americas. With a body length of up to and a weight of up to , it is the largest cat species in the Americas and the th ...
, Steamroller, Puma,
Excavator Excavators are heavy construction equipment consisting of a boom, dipper (or stick), bucket and cab on a rotating platform known as the "house". The house sits atop an undercarriage with tracks or wheels. They are a natural progression fr ...
&
Zen Zen ( zh, t=禪, p=Chán; ja, text= 禅, translit=zen; ko, text=선, translit=Seon; vi, text=Thiền) is a school of Mahayana Buddhism that originated in China during the Tang dynasty, known as the Chan School (''Chánzong'' 禪宗), and ...
-based) * (2014+) Intel 5th & 6th gen processors ( Broadwell, Skylake) * (2015+) Qualcomm Adreno 5xx series * (2018+) Qualcomm Adreno 6xx series * (2017+) ARM Mali (Bifrost) G51 and G71 in Android 7.1 and Linux * (2018+) ARM Mali (Bifrost) G31, G52, G72 and G76 * (2017+) incomplete Evaluation support: Nvidia
Kepler Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws o ...
,
Maxwell Maxwell may refer to: People * Maxwell (surname), including a list of people and fictional characters with the name ** James Clerk Maxwell, mathematician and physicist * Justice Maxwell (disambiguation) * Maxwell baronets, in the Baronetage of ...
,
Pascal Pascal, Pascal's or PASCAL may refer to: People and fictional characters * Pascal (given name), including a list of people with the name * Pascal (surname), including a list of people and fictional characters with the name ** Blaise Pascal, Frenc ...
, Volta and Turing GPU's (GeForce 600, 700, 800, 900 & 10-series, Quadro K-, M- & P-series, Tesla K-, M- & P-series) with Driver Version 378.66+


OpenCL 1.2 support

* (2011+) for some AMD GCN 1st Gen some OpenCL 2.0 Features not possible today, but many more Extensions than Terascale * (2009+) AMD TeraScale 2 & 3 GPU's (RV8xx, RV9xx in HD 5000, 6000 & 7000 Series) * (2011+) AMD TeraScale APU's ( K10,
Bobcat The bobcat (''Lynx rufus''), also known as the red lynx, is a medium-sized cat native to North America. It ranges from southern Canada through most of the contiguous United States to Oaxaca in Mexico. It is listed as Least Concern on the ...
& Piledriver-based) * (2012+) Nvidia Kepler, Maxwell, Pascal, Volta and Turing GPU's (GeForce 600, 700, 800, 900, 10, 16, 20 series, Quadro K-, M- & P-series, Tesla K-, M- & P-series) * (2012+) Intel 3rd & 4th gen processors ( Ivy Bridge, Haswell) * (2013+) Qualcomm Adreno 4xx series * (2013+)
ARM Mali In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between the ...
Midgard 3rd gen (T760) * (2015+)
ARM Mali In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between the ...
Midgard 4th gen (T8xx)


OpenCL 1.1 support

* (2008+) some AMD TeraScale 1 GPU's (RV7xx in HD4000-series) * (2008+) Nvidia Tesla, Fermi GPU's (GeForce 8, 9, 100, 200, 300, 400, 500-series, Quadro-series or Tesla-series with Tesla or
Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and t ...
GPU) * (2011+) Qualcomm Adreno 3xx series * (2012+) ARM Mali Midgard 1st and 2nd gen (T-6xx, T720)


OpenCL 1.0 support

* mostly updated to 1.1 and 1.2 after first Driver for 1.0 only


Portability, performance and alternatives

A key feature of OpenCL is portability, via its abstracted memory and
execution model A programming language consists of a grammar/syntax plus an execution model. The execution model specifies the behavior of elements of the language. By applying the execution model, one can derive the behavior of a program that was written in term ...
, and the programmer is not able to directly use hardware-specific technologies such as inline
Parallel Thread Execution Parallel Thread Execution (PTX or NVPTX) is a low-level parallel thread execution virtual machine and instruction set architecture used in Nvidia's CUDA programming environment. The NVCC compiler translates code written in CUDA, a C++-like lan ...
(PTX) for Nvidia GPUs unless they are willing to give up direct portability on other platforms. It is possible to run any OpenCL kernel on any conformant implementation. However, performance of the kernel is not necessarily portable across platforms. Existing implementations have been shown to be competitive when kernel code is properly tuned, though, and auto-tuning has been suggested as a solution to the performance portability problem, yielding "acceptable levels of performance" in experimental linear algebra kernels. Portability of an entire application containing multiple kernels with differing behaviors was also studied, and shows that portability only required limited tradeoffs. A study at Delft University from 2011 that compared
CUDA CUDA (or Compute Unified Device Architecture) is a parallel computing platform and application programming interface (API) that allows software to use certain types of graphics processing units (GPUs) for general purpose processing, an approach ...
programs and their straightforward translation into OpenCL C found CUDA to outperform OpenCL by at most 30% on the Nvidia implementation. The researchers noted that their comparison could be made fairer by applying manual optimizations to the OpenCL programs, in which case there was "no reason for OpenCL to obtain worse performance than CUDA". The performance differences could mostly be attributed to differences in the programming model (especially the memory model) and to NVIDIA's compiler optimizations for CUDA compared to those for OpenCL. Another study at D-Wave Systems Inc. found that "The OpenCL kernel’s performance is between about 13% and 63% slower, and the end-to-end time is between about 16% and 67% slower" than CUDA's performance. The fact that OpenCL allows workloads to be shared by CPU and GPU, executing the same programs, means that programmers can exploit both by dividing work among the devices. This leads to the problem of deciding how to partition the work, because the relative speeds of operations differ among the devices.
Machine learning Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence. Machine ...
has been suggested to solve this problem: Grewe and O'Boyle describe a system of support-vector machines trained on compile-time features of program that can decide the device partitioning problem statically, without actually running the programs to measure their performance. In a comparison of actual graphic cards of AMD RDNA 2 and Nvidia RTX Series there is an undecided result by OpenCL-Tests. Possible performance increases from the use of Nvidia CUDA or OptiX were not tested.


See also

* Advanced Simulation Library *
AMD FireStream AMD FireStream was AMD's brand name for their Radeon-based product line targeting stream processing and/or GPGPU in supercomputers. Originally developed by ATI Technologies around the Radeon X1900 XTX in 2006, the product line was previously ...
* BrookGPU *
C++ AMP C, or c, is the third letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''cee'' (pronounced ), plural ''cees''. History "C" ...
*
Close to Metal In computing, Close To Metal ("CTM" in short, originally called ''Close-to-the-Metal'') is the name of a beta version of a low-level programming interface developed by ATI, now the AMD Graphics Product Group, aimed at enabling GPGPU computing. CTM ...
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CUDA CUDA (or Compute Unified Device Architecture) is a parallel computing platform and application programming interface (API) that allows software to use certain types of graphics processing units (GPUs) for general purpose processing, an approach ...
* DirectCompute * GPGPU * HIP * Larrabee * Lib Sh * List of OpenCL applications * OpenACC *
OpenGL OpenGL (Open Graphics Library) is a cross-language, cross-platform application programming interface (API) for rendering 2D and 3D vector graphics. The API is typically used to interact with a graphics processing unit (GPU), to achieve hardwa ...
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OpenHMPP OpenHMPP (HMPP for Hybrid Multicore Parallel Programming) - programming standard for heterogeneous computing. Based on a set of compiler directives, standard is a programming model designed to handle hardware accelerators without the complexity ...
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OpenMP OpenMP (Open Multi-Processing) is an application programming interface (API) that supports multi-platform shared-memory multiprocessing programming in C, C++, and Fortran, on many platforms, instruction-set architectures and operating syst ...
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Metal A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...
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RenderScript RenderScript is a component of the Android operating system for mobile devices that offers an API for acceleration that takes advantage of heterogeneous hardware. It allows developers to increase the performance of their applications at the cost of ...
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SequenceL SequenceL is a general purpose functional programming language and auto-parallelizing (Parallel computing) compiler and tool set, whose primary design objectives are performance on multi-core processor hardware, ease of programming, platform porta ...
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SIMD Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it shoul ...
* SYCL * Vulkan *
WebCL WebCL (Web Computing Language) is a JavaScript binding to OpenCL for Heterogeneous computing, heterogeneous parallel computing within any compatible web browser without the use of Plug-in (computing), plug-ins, first announced in March 2011. It is ...


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WebCL WebCL (Web Computing Language) is a JavaScript binding to OpenCL for Heterogeneous computing, heterogeneous parallel computing within any compatible web browser without the use of Plug-in (computing), plug-ins, first announced in March 2011. It is ...

International Workshop on OpenCL
( IWOCL) sponsored by The Khronos Group {{Parallel computing 2009 software Application programming interfaces Cross-platform software GPGPU OpenCL Parallel computing Graphics libraries Graphics standards