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catomiccuda

Some issue with Atomic add in CUDA kernel operation

I'm having a issue with my kernel.cu class

Calling nvcc -v kernel.cu -o kernel.o I'm getting this error:

kernel.cu(17): error: identifier "atomicAdd" is undefined

My code: 

#include "dot.h"
#include <cuda.h>
#include "device_functions.h" //might call atomicAdd

__global__ void dot (int *a, int *b, int *c){
    __shared__ int temp[THREADS_PER_BLOCK];
    int index = threadIdx.x + blockIdx.x * blockDim.x;
    temp[threadIdx.x] = a[index] * b[index];

    __syncthreads();

    if( 0 == threadIdx.x ){
        int sum = 0;
        for( int i = 0; i<THREADS_PER_BLOCK; i++)
            sum += temp[i];
        atomicAdd(c, sum);
    }
}

Some suggest?

Solution

  • You need to specify an architecture to nvcc which supports atomic memory operations (the default architecture is 1.0 which does not support atomics). Try:

    nvcc -arch=sm_11 -v kernel.cu -o kernel.o

    and see what happens.

    EDIT in 2015 to note that the default architecture in CUDA 7.0 is now 2.0, which supports atomic memory operations, so this should not be a problem in newer toolkit versions.