Links:

• Data Parallel C++ Book

• Examples in C++

• Examples in DPC++

Always use in code:

#include  <CL/sycl.hpp>

Using namespace  sycl;

1. Memory Management

Malloc

To manage memory use a pointer-based approach, more specifically Malloc. For example, create memory location to share:

char *example = malloc_shared<char>(variable,queue);

In SYCL you can use 3 types: malloc_host, malloc_shared and malloc_device:

int* host_array = malloc_host(N, Q);
int* shared_array = malloc_shared(N, Q);
int* device_array = malloc_device(N, Q);

Characteristics:

Buffer

Another option is the use of buffers: The easiest way to declare them is by indicating the data source in their constructor: array, vector, pointer, etc. Example:

buffer  my_buffer(my_data);

To access these you must use an ‘accessor’

Example:

accessor  my_accessor(my_buffer, h)

2. Implementation and management of Kernels

Queues

The queues allow us to connect with the devices, with them we send kernels to execute work and move data.

Queue <queue name>;

Parallel_for

It allows to define a parallel loop that will be executed by many threads depending on the number of iterations. In its simplified version, the compiler performs the division of work (iterations) in the threads.

h.parallel_for (range {N}, [=] (id <1> idx) {

As you can see it is like a lambda function, the function takes two arguments, the first is called a range which specifies the number of elements to throw in each dimension and the second is a kernel function that will be executed for each index of the range .

Note: They can use for several dimensions, for two dimensions it would be:

h.parallel_for (range {N, M}, [=] (id <2> idx)

A complete code example:

#include <CL/sycl.hpp>
#include <array>
#include <iostream>

using namespace sycl;

int main(){
	constexpr int size = 16;
	std::array<int, size> data;

	queue Q;
	buffer B { data };
	Q.submit([&](handler& h){
	accessor A{B,h};

	h.parallel_for(size, [=](auto& idx){
		A[idx] = idx;
		});
	});


	host_accessor A{B};
	for(int i=0; i<size; i++)
	std::cout << "data" << i << " = " << A[i] << "\n";

return 0;
}