ColossalAI/colossalai/kernel/cuda_native/csrc/gptq/cu_compat.cuh

// Adapted from turboderp exllama: https://github.com/turboderp/exllama

#ifndef _cuda_compat_cuh
#define _cuda_compat_cuh

// atomicAdd for half types, to support CC < 7.x

__device__ __forceinline__ void atomicAdd_half(half* address, half val)
{
    unsigned int * address_as_ui = (unsigned int *) ((char *)address - ((size_t)address & 2));
    unsigned int old = *address_as_ui;
    unsigned int assumed;

    do
    {
        assumed = old;
        __half_raw hsum;
        hsum.x = (size_t)address & 2 ? (old >> 16) : (old & 0xffff);
        half tmpres = __hadd(hsum, val);
        hsum = __half_raw(tmpres);
        old = (size_t)address & 2 ? (old & 0xffff) | (hsum.x << 16) : (old & 0xffff0000) | hsum.x;
        old = atomicCAS(address_as_ui, assumed, old);
    }
    while (assumed != old);
}

// atomicAdd for half2 types

__device__ __forceinline__ void atomicAdd_half2(half2* address, half2 val)
{
    unsigned int* address_as_ui = (unsigned int*)address;
    unsigned int old = *address_as_ui;
    unsigned int assumed;
    do
    {
        assumed = old;
        half2 old_val = *((half2*)&old);
        half2 new_val = __hadd2(old_val, val);
        old = atomicCAS(address_as_ui, assumed, *((unsigned int*)&new_val));
    }
    while (assumed != old);
}

//

#if defined(__CUDA_ARCH__) || defined(USE_ROCM)
#if __CUDA_ARCH__ < 700 || defined(USE_ROCM)

__device__ __forceinline__ void atomicAdd(half* address, half val) { atomicAdd_half(address, val); }

#if __CUDA_ARCH__ < 600 || defined(USE_ROCM)
__device__ __forceinline__ void atomicAdd(half2* address, half2 val) { atomicAdd_half2(address, val); }
#endif

#endif
#endif

#endif