Book Image

OpenCL Programming by Example

Book Image

OpenCL Programming by Example

Overview of this book

Research in parallel programming has been a mainstream topic for a decade, and will continue to be so for many decades to come. Many parallel programming standards and frameworks exist, but only take into account one type of hardware architecture. Today computing platforms come with many heterogeneous devices. OpenCL provides royalty free standard to program heterogeneous hardware. This guide offers you a compact coverage of all the major topics of OpenCL programming. It explains optimization techniques and strategies in-depth, using illustrative examples and also provides case studies from diverse fields. Beginners and advanced application developers will find this book very useful. Beginning with the discussion of the OpenCL models, this book explores their architectural view, programming interfaces and primitives. It slowly demystifies the process of identifying the data and task parallelism in diverse algorithms. It presents examples from different domains to show how the problems within different domains can be solved more efficiently using OpenCL. You will learn about parallel sorting, histogram generation, JPEG compression, linear and parabolic regression and k-nearest neighborhood, a clustering algorithm in pattern recognition. Following on from this, optimization strategies are explained with matrix multiplication examples. You will also learn how to do an interoperation of OpenGL and OpenCL. "OpenCL Programming by Example" explains OpenCL in the simplest possible language, which beginners will find it easy to understand. Developers and programmers from different domains who want to achieve acceleration for their applications will find this book very useful.
Table of Contents (18 chapters)
OpenCL Programming by Example
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Image access qualifiers


OpenCL specification provides two types of access qualifiers for different types of image memory objects. They can be either read_only or write_only. In the following example imageA is read-only image object, and imageB is a write-only image object:

__kernel void foo (read_only image2d_t imageA,
                   write_only image2d_t imageB)

About function qualifiers and attributes, __kernel qualifier declares a function which is defined explicitly to run on an OpenCL device. A __kernel qualified function can be invoked inside another kernel function. In such a situation the kernel function just behaves as another function call. There are optional function attributes which can be specified for kernel functions.

The __kernel qualified functions cannot return any data type. The return type is always void for those functions.

The keyword __attribute__ allows you to specify the special attributes for enums, structs, unions, or to the functions or kernels. An attribute specifier...