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

Event profiling


Profiling is an important tool, which must be used for tuning any high performance application. OpenCL provides this mechanism by making the cl_event objects to hold the timing information. This timing information can be captured using the clGetEventProfilingInfo function. The command_queue queue should be created with CL_QUEUE_PROFILING_ENABLE flag set as properties argument in clCreateCommandQueue.

If the queue is enabled for profiling then the following function returns profiling information for the enqueued task associated with the event object:

cl_int clGetEventProfilingInfo (cl_event event,cl_profiling_info param_name,size_t param_value_size,void *param_value,size_t *param_value_size_ret)

All the timestamps CL_PROFILING_COMMAND_[QUEUED|SUBMIT|START|END] can be obtained using this function. The returned value is a 64 bit cl_ulong value, which specifies the device time counter in nanoseconds. You can determine the time of when the command got enqueued|submitted|started|ends...