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

Querying buffer objects


As any other OpenCL objects, cl_mem objects can be queried to return information regarding how they are constructed, their status, reference count, and so on. The OpenCL function clGetMemObjectInfo helps in this.

cl_int 
clGetMemObjectInfo (cl_mem memobj,cl_mem_info param_name,size_t param_value_size,void *param_value,size_t *param_value_size_ret)

This function is similar to the clGetDeviceInfo discussed in Chapter 2, OpenCL Architecture. The param_name is a parameter specific to this function and is of type cl_mem_info. It can be used for both image and buffer type cl_mem objects. The following code snippet shows you how to retrieve the flags associated with a cl_mem object.

// Create memory buffers on the device for each vector
cl_mem A_clmem = clCreateBuffer(context,CL_MEM_READ_ONLY|CL_MEM_USE_HOST_PTR,VECTOR_SIZE * sizeof(float), A_ptr, &clStatus);
...
...
...
cl_mem_flags flags;
clStatus = clGetMemObjectInfo (A_clmem,CL_MEM_FLAGS,sizeof(cl_mem_flags),&flags...