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

Reading and writing buffers


By now you know how to create buffer objects and how to read them in the kernel. Before the kernel is launched you may want to write the buffer to the device memory using the API clEnqueueWriteBuffer. And after the kernel has completed processing, you will want to get the buffer back to the host from the device memory. This can be achieved by using the clEnqueueReadBuffer function.

cl_int clEnqueueWriteBuffer (cl_command_queue command_queue,cl_mem buffer,cl_bool blocking_write,size_t offset,size_t size,const void *ptr,cl_uint num_events_in_wait_list,const cl_event *event_wait_list,cl_event *event)

This function writes data from the host to the device memory. Following are the descriptions of the parameters passed.

Parameter name

Description

command_queue

The write command will be queued in this OpenCL queue. One should make sure that the cl_mem object buffer and the command_queue are created using the same context.

buffer

A valid cl_mem buffer object, which...