Change Structure of syclacademy

[hdelan]

The current structure of syclacademy presents the buffer/accessor model before USM. This chapter makes the assumption that the programmer knows the difference between device and host memory, as well as the need for memcpys etc. It also presents buffers and accessors without any motivation as to why we need them/why they are useful.

Now that USM is a core feature I think a better structure would be to present USM before buffers accessors, since it emphasizes what the buffer accessor model abstracts away. Ideally dependencies would also be covered before introducing the buf acc model, as this is another thing that the buff acc model abstracts away.

A proposed ordering of topics would be:

USM -> Simple kernels (single tasks) -> Dependencies -> buffers/accessors

These units may have other topics interspersed between them.

This means that by the time we learn about the buffer/accessor model, we are fully convinced of why they are important and useful. Instead of the current approach which presents them in the SYCL 1.2.1 context of 'this is how you manage data'.