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Device function pointers as structure elements

I have this (working) processor code:

#define NF 3
int ND;

typedef double (*POT)(double x, double y);

typedef struct {
    POT pot[NF];
} DATAMPOT;

DATAMPOT *datampot;

double func0(double x, double y);
double func1(double x, double y);
double func2(double x, double y);


int main(void)
{
    int i;

    ND=5;
    datampot=(DATAMPOT *)malloc(ND*sizeof(DATAMPOT));

    for(i=0;i<ND;i++){
        datampot[i].pot[0]=func0;
        datampot[i].pot[1]=func1;
        datampot[i].pot[2]=func2;
    }

    return 0;
}

Now I will try a GPU version like this

#define NF 3
int ND;

typedef double (*POT)(double x, double y);

typedef struct {
    POT pot[NF];
} DATAMPOT;

DATAMPOT *dev_datampot;

__device__ double z_func0(double x, double y);
__device__ double z_func1(double x, double y);
__device__ double z_func2(double x, double y);

__global__ void assign(DATAMPOT *dmp, int n)
{
    int i;

    for(i=0;i<n;i++){
        (dmp+i)->pot[0]=z_func0;
        (dmp+i)->pot[1]=z_func1;
        (dmp+i)->pot[2]=z_func2;
    }

}

int main(void)
{
    int i;

    ND=5;
    cudaMalloc((void**)&dev_datampot,ND*sizeof(DATAMPOT));

    assign<<<1,1>>>(dev_datampot,ND);

    return 0;
}

but the assignment of device function pointers does not work. Where is the mistake? And how can this be fixed? Thank you very much in advance. Michelle

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3 answers


Hope this helps someone



#define NF 3
int ND;

typedef double (*POT)(double x, double y);

typedef struct {
    POT pot[NF];
} DATAMPOT;

DATAMPOT *dev_datampot;

__device__ double z_func0(double x, double y);
__device__ double z_func1(double x, double y);
__device__ double z_func2(double x, double y);

//Static pointers to the above device functions    
__device__ POT z_func0_pointer=z_func0;  
__device__ POT z_func1_pointer=z_func1;
__device__ POT z_func2_pointer=z_func2;



int main(void)
{
    int i;
    POT pot_pointer;

    ND=5;
    cudaMalloc((void**)&dev_datampot,ND*sizeof(DATAMPOT));

    for(i=0;i<ND;++i){  
     cudaMemcpyFromSymbol( &pot_pointer,z_func0_pointer, sizeof( POT ) );
  cudaMemcpy(&dev_datampot[i].pot[0]),&pot_pointer,sizeof(POT),cudaMemcpyHostToDevice);

     cudaMemcpyFromSymbol( &pot_pointer,z_func1_pointer, sizeof( POT ) );
  cudaMemcpy(&dev_datampot[i].pot[1]),&pot_pointer,sizeof(POT),cudaMemcpyHostToDevice);

     cudaMemcpyFromSymbol( &pot_pointer,z_func2_pointer, sizeof( POT ) );
  cudaMemcpy(&dev_datampot[i].pot[2]),&pot_pointer,sizeof(POT),cudaMemcpyHostToDevice);
    }

    return 0;
}
+1


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According to the CUDA C Programming Guide ,

D.2.4.3 Function pointers

Function pointers are __global__

supported in host code but not device code.

Function pointers to functions are __device__

supported only in device code compiled for devices with 2.x computability.

You cannot accept a function address __device__

in the main code.



I am assuming you are compiling for computational power that is below 2.0.

+1


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What's your compiler option? On a device with a computing power of 1.3 or below, the device function must be built-in, so you cannot use the device function pointer.

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