OpenCL: offset for accessing float2*/float4*/... elements - opencl

Question

I currently have something like this in my kernel code:
func(__global float2 *array, __global float *buffer) {
float *vector[2];
vector[0] = array.s0;
vector[1] = array.s1;
So I can do something like this later in the code:
vector[vec_off][index] = buffer[i];
Basically, I want to be able to access the elements of a float2 in my code based on a calculated index. The point is to be able to easily expand it to a float4/float16 vector later on.
Currently I get a (-11) error (CL_BUILD_PROGRAM_FAILURE) when I try to do vector[0] = array.x; Which I guess means I'm not allowed to write it (like that?) in OpenCL.
If it's not just a syntax error, I should be able to do this by accessing each element of array using an offset, so I would have:
array.s0 = array
array.s1 = array + offset
...
array.sf = array + 15 * offset
I do not know however how a floatn is stored in memory. Is the .s1 part stored right after the .s0? Is that is the case, then offset would just be the size of array.s0, right?
Thank you.

Answer 1

To be able to use calculated index to access float2 elements you can use union or cast directly to float*:
1. Using union
Define the following union:
union float_type
{
float2 data2;
float data[2];
};
and then cast float2 array on the fly and access elements using calculated index:
func(__global float2 *array, __global float *buffer) {
float foo = ((__global union float_type*)array)[1].data[1];
}
2. cast to float*
func(__global float2 *array, __global float *buffer) {
float foo = ((__global float*)&array[1])[1];
}