Why doesn't this OpenCL kernel work? - objective-c

Question

I am trying to write a physics emulator for Mac which uses OpenCL hardware acceleration. Right now, when I try to run my kernel with OpenCL, the debugger reports a SIGABORT at my gcl_memcpy line to get results from the kernel.
Right now, I have managed to simplify the code quite a bit and still get the error. Here is my barebones OpenCL kernel which still causes a crash:
kernel void pointfield(global const float * points,
float posX, float posY,
global float * fieldsOut) {
size_t index = get_global_id(0);
float2 chargePosition = vload2(0, &points[index * 3]);
vstore2(chargePosition, 0, &fieldsOut[2 * index]);
}
This literally just loads a 2-dimensional vector and then stores it immediately. And I know what you are thinking, but the problem is not an overflow error. This equivalent code works:
kernel void pointfield(global const float * points,
float posX, float posY,
global float * fieldsOut) {
size_t index = get_global_id(0);
fieldsOut[2 * index] = points[3 * index];
fieldsOut[2 * index + 1] = points[3 * index + 1];
}
What on EARTH is wrong with my vector code?
Also, incase it seems necessary, here is the gist of how I am creating the OpenCL context:
dispatch_queue_t queue = gcl_create_dispatch_queue(CL_DEVICE_TYPE_GPU, NULL);
if (!queue) {
queue = gcl_create_dispatch_queue(CL_DEVICE_TYPE_CPU, NULL);
}
cl_device_id gpu = gcl_get_device_id_with_dispatch_queue(queue);
char name[128];
clGetDeviceInfo(gpu, CL_DEVICE_NAME, 128, name, NULL);
dispatch_sync(queue, ^{
cl_ndrange range = {
1,
{0, 0, 0},
{self.pointChargeCount, 0, 0},
0
};
pointfield_kernel(&range, (cl_float *)_pointCharges.clBuffer, point.x, point.y,
(cl_float *)_fieldValues.clBuffer);
[_fieldValues getCLBuffer]; // calls gcl_memcpy
});
If I omit the [_fieldValues getCLBuffer] call, the abort happens at the end of the dispatch_sync call rather than at the gcl_memcpy call.