Sycl Academy LogoSycl Academy Logo
listShow Lessons List
  1. What is SYCL
  2. Enqueueing a Kernel
  3. Managing Data
  4. Handling Errors
  5. Device Discovery
  6. Data Parallelism
  7. Introduction to USM
  8. Using USM
  9. Asynchronous Execution
  10. Data and Dependencies
  11. In Order Queue
  12. Advanced Data Flow
  13. Multiple Devices
  14. ND Range Kernels
  15. Image Convolution
  16. Coalesced Global Memory
  17. Vectors
  18. Local Memory Tiling
  19. Further Optimisations
  20. Matrix Transpose
  21. More SYCL Features
  22. Functors
Lesson
Source
Solution
GitHub Iconedit

Using USM

In this exercise you will learn how to use the USM API to write a SYCL application which performs a vector add.

1.) Allocate data on the host

Allocate memory on the host for the input and out data just as you did when using the buffer/accessor model.

2.) Create a queue

Create a queue using the USM device selector from the "Introduction to USM" exercise, remember to handle errors.

3.) Allocate device memory

When using the USM model the first thing you need to do is allocate the USM device memory.

To do this call malloc_device to allocate memory for the two inputs and the output.

4.) Copy to the device

Before you can perform any computation on the data you must copy it to the device.

To do this call the queue member function memcpy for each of the two inputs, remember to call wait on the event that is returned.

5.) Define the kernel function

Now you can define the kernel function itself, which is largely the same as in the "Data Parallelism" exercise.

This can be done differently from the buffer/accessor model, by calling the shortcut member function parallel_for on the queue rather than creating a command group.

Note that as you are accessing a pointer rather than an accessor you must retrieve an integral index, which can be done by calling the subscript operator on the id passed into the kernel function, with index 0.

Remember to name your kernel function, and to call wait on the event that is returned.

6.) Copy back the result

Once the kernel function has completed you can copy the result back to the host.

As you did when copying to the device, you can do this by calling the queue member function memcpy, again remember to call wait on the event that is returned.

7.) Free the device memory

Finally once you have copied the data back from the device you can free that memory.

To do this call free on each of the USM device allocations, note this is the SYCL API free and not the standard C free.

Build And Execution Hints

For DevCloud via JupiterLab follow these instructions.

For DPC++: instructions.

For AdaptiveCpp: instructions.