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

Undefined behavior of the cl_mem objects


An OpenCL memory model, being a relaxed memory architecture, specifies some restrictions or undefined behavior around the cl_mem object. These undefined behaviors occur mostly when there is a simultaneous read and write to a buffer. Following are listed some undefined scenarios:

  • If the buffer is created with CL_MEM_WRITE_ONLY flag and the kernel reads from this buffer pointer on the devices side, then it's an undefined behavior. That means reading from a CL_MEM_WRITE_ONLY buffer inside the kernel is undefined.

  • Similarly writing to a buffer created using the flag CL_MEM_READ_ONLY is undefined inside the kernel.

  • It is possible to create two OpenCL cl_mem buffers from the same host memory using the CL_MEM_USE_HOST_PTR flag. There may be an overlapping memory region. If one or more commands enqueued to the command queue operate on the two cl_mem objects but pointing to the same host memory host_ptr, then such an operation is not defined. It is the application...