substitutions for cl_khr_int64_base_atomics - opencl

Question

I have an ATI Firepro V4800 graphics card which does not support cl_khr_int64_base_atomics. I am trying to adapt the RadixSort algo for long integers. The algo uses atomic_inc, the 64-bit of which is atom_inc, which I cannot use in the kernel. So, my question is, is there a piece of code which performs the same function as atomic_inc which can be used? The piece of kernel code is given below:
__kernel void histogram(__global uint* unsortedData,
__global uint* buckets,
uint shiftCount,
__local uint* sharedArray)
{
size_t localId = get_local_id(0);
size_t globalId = get_global_id(0);
size_t groupId = get_group_id(0);
size_t groupSize = get_local_size(0);
uint numGroups = get_global_size(0) / get_local_size(0);
// Initialize shared array to zero //
sharedArray[localId] = 0;
barrier(CLK_LOCAL_MEM_FENCE);
// Calculate thread-histograms //
uint value = unsortedData[globalId];
value = value >> shiftCount & 0xFFU;
atomic_inc(sharedArray+value);
barrier(CLK_LOCAL_MEM_FENCE);
// Copy calculated histogram bin to global memory //
uint bucketPos = groupId * groupSize + localId ;
//uint bucketPos = localId * numGroups + groupId ;
buckets[bucketPos] = sharedArray[localId];
}
Any suggestions? Thank you.
Edit:
Another way for the same is given in this blogsite: http://suhorukov.blogspot.in/2011/12/opencl-11-atomic-operations-on-floating.html. This gives a very generic implementation of the Atomic Inc.

Answer 1

You could try something like this:
void atomInc64 (__local uint *counter)
{
uint old, carry;
old = atomic_inc (&counter [0]);
carry = old == 0xFFFFFFFF;
atomic_add (&counter [1], carry);
}
Where counter is an array of two 32-bit integers. While the two halves don't increment at exactly the same time, the total should be correct when the program completes.