How to assign pointer to element of array of some struct in this array(OpenCL)?

Question

May be you can advise me how to create a hierarchical structure in OpenCL. It is easy if you have "new" or "malloc", but I don't know how do it in GPGPU. So I created 3 kernels:

1. To send sizeof struct to host.
2. To initialize data.
3. And kernel which uses data initialized in second kernel.

I have this struct in OpenCL:

    typedef struct some some;
struct some{
    char data[4];
    some* children[8];
};

First kernel says that size of this structure is 36 bytes(4 for data and 32 for pointers).

Next I allocate memory on GPU based on previous information and call second kernel:

kernel void import(global some *buffer){
for(int i=0;i<4;i++){
buffer[0].data[i]=255; //For example, doesn't matter
}
//Now I need to assign pointer to next element of array(buffer) to first element
buffer[0].children[0]=&buffer[1];
}

But kernel not compiles. Also I tried:

*buffer[0].children[0]=buffer[0];

It compiles, but crashes of course. It is logically wrong) Without assignments of pointers everything works fine. Very cool program for 1 element)

Answer 1

Try using offsets or array indices instead of pointers.

typedef struct some some; struct some{ char data[4]; size_t children[8]; // an array of subscripts };

...

// buffer[0].children[0]=&buffer[1]; becomes buffer[0].children[0] = 1;

So now you can reference a child via its subscript

buffer[ buffer[0].children[0] ].char[0]

Answer 2

If your device supports OpenCL 2.0 then you can use Shared Virtual Memory . The pointers created on the host will be valid on the device too.

The description of Shared Virtual Memory concept and the examples you can find here and here .