asgard4 writes "In recent years GPUs have become powerful computing devices whose power is not only used to generate pretty graphics on screen but also to perform heavy computation jobs that were exclusively reserved for high performance super computers in the past. Considering the vast diversity and rapid development cycle of GPUs from different vendors, it is not surprising that the ecosystem of programming environments has flourished fairly quickly as well, with multiple vendors, such as NVIDIA, AMD, and Microsoft, all coming up with their own solutions on how to program GPUs for more general purpose computing (also abbreviated GPGPU) applications. With OpenCL (short for Open Computing Language) the Khronos Group provides an industry standard for programming heavily parallel, heterogeneous systems with a language to write so-called kernels in a C-like language. The OpenCL Programming Guide gives you all the necessary knowledge to get started developing high-performing, parallel applications for such systems with OpenCL 1.1." Keep reading for the rest of asgard4's review.The authors of the book certainly know what they are talking about. Most of them have been involved in the standardization effort that went into OpenCL. Munshi, for example, is the editor of the OpenCL specification. So all the information in the book is first-hand knowledge from experts in OpenCL. The reader is expected to be familiar with the C programming language and basic programming concepts. Some experience in parallelizing problems is a benefit but not a requirement.
The book consist of two major parts. The first part is a detailed description of the OpenCL C language and the API used by the host to control the execution of programs written in that language. The second part is comprised of various case studies that show OpenCL in action.
The authors get straight to the point in the introduction, discussing the conceptual foundations of OpenCL in detail. They explain what kernels are (basically functions that are scheduled for execution on a compute device), how the kernel execution model works, how the host manages the command queues that schedule memory transfers or kernel execution on compute devices, and the memory model.
While this first chapter is all prose, the second chapter dives right in with some code and a first HelloWorld example. The following chapters introduce more and more of the OpenCL language and API step-by-step. All API functions are described in somewhat of a reference style with a lot of detail, including possible error codes. However, the text is not a reference. There is always a good explanation with examples or short code listings, the only notable exception being chapter three, which presents the OpenCL C language. A few more examples would have made the text less dry in this chapter.
An important chapter is chapter nine on events and synchronization between multiple compute devices and the host. This chapter is important because — as any experienced parallel programmer knows — getting synchronization right is often tricky but obviously essential for correct execution of a parallel program.
An interesting feature in OpenCL is the built-in interoperability with OpenGL and, surprisingly, Direct3D. Various functions in the OpenCL API allow creating buffers from OpenGL/Direct3D objects, such as textures or vertex buffers, that can be used by an OpenCL kernel. This opens up interesting possibilities for doing a lot more work on the GPU in graphics applications, such as running a fluid simulation on the GPU in OpenCL, which directly writes its results into vertex buffers or textures to be used directly for rendering without the host CPU having to intervene.
Before delving into the case studies the book briefly discusses the embedded profile that is available for OpenCL and the standardized C++ API that the Khronos Group provides in addition to the regular OpenCL API (which is defined exclusively as C functions). The C++ API makes using some of the OpenCL objects a little bit easier and somewhat nicer.
The second part of the book contains various interesting case studies that show off what OpenCL can be used for, such as computing a sobel filter or a histogram for an image, computing FFTs, doing cloth simulation, or multiplying dense and sparse matrices. The choice and variety of case studies is definitely interesting and most will be immediately applicable to the reader when going forward developing applications using OpenCL. All the code for the examples and the case studies in the book are available for download on the book's website.
Overall, the OpenCL Programming Guide succeeds in being a great introduction to OpenCL 1.1. The book covers all of the specification and more, has an easy to read writing style and yet provides all the necessary details to be an all-encompassing guide to OpenCL. The good selection of case studies makes the book even more appealing and demonstrates what can be done with real-life OpenCL code (and also how it needs to be optimized to get the best performance out of current OpenCL platforms, such as GPUs).
Martin Ecker has been involved in real-time graphics programming for more than 15 years and works as a professional game developer for Sony Computer Entertainment America in sunny San Diego, California.
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