usmhelloworld

This sample shows basics of Unified Shared Memory. Application implements a simple copy buffer kernel and demonstrates essential operations related to the USM:

• Memory allocation
• Memory reads and writes
• Passing USM to OpenCL kernels

Source code is organized in a way to highlight similarities and differences between USM types: host, device and shared. To change used USM type just pass its name from a command line as an positional argument.

It is also possible to change allocation size simply by passing --size N option from a command line. N is a number of elements to allocate and each element has 4 bytes (cl_uint).

Basic structure of an application using USM is presented below:

1. Check if cl_intel_unified_shared_memory extension is reported by a device.
2. Check if all required USM capabilities are supported.
3. Allocate memory using:
   1. clHostMemAllocINTEL;
   2. clDeviceMemAllocINTEL;
   3. clSharedMemAllocINTEL;
   4. malloc/new;
4. Populate memory using for example:
   1. memcpy/std::copy/clEnqueueMemcpyINTEL;
   2. memset/std::fill/clEnqueueMemsetINTEL;
5. Create kernel.
6. Set memory as kernel argument using clSetKernelArgMemPointerINTEL.
7. Run kernel.
8. Read results using for example:
   1. memcpy/std::copy/clEnqueueMemcpyINTEL;
9. Free memory using clMemFreeINTEL.

Usage

usm_hello_world host
usm_hello_world device
usm_hello_world shared
usm_hello_world host --size 1024