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

Mapping image objects


As discussed in the mapping of buffer objects in the previous chapter, images can also be mapped to a host pointer. Images computed at the device may sometimes needs to be available at the host address space, say for writing the image back to the file system. The clEnqueueMapImage function will map the image from the device memory to the host address space. This is also a task which is enqueued on the device command_queue.

void * clEnqueueMapImage (cl_command_queue command_queue,cl_mem image,cl_bool blocking_map,cl_map_flags map_flags,const size_t *origin,const size_t *region,size_t *image_row_pitch,size_t *image_slice_pitch,cl_uint num_events_in_wait_list,const cl_event *event_wait_list,cl_event *event,cl_int *errcode_ret)

The clEnqueueMapImage function enqueue a command to map a region of the device buffer in the image object to host accessible buffer. Note that the return type of this function is void *.

  • image: It is the valid image cl_mem object

  • blocking_map: This is...