Asking for help on a basic excersize

I start a small cuda program (only test the correctness)
and I can get correct result when using device emulation mode
but when I turn to GPU mode, the result is wrong.

Can anyone help me? Thank you in advance.

The program is only to sum ten numbers.

The following is my program. (On windows XP, Geforece 8800GT, cuda2.0)

#include <stdio.h>
#define THREAD_NUM 1

global void sump_on_device(int* number,int size, int *sum)
{
const int tid=threadIdx.x;

int myfrom,myend,avgsize;


avgsize=size/THREAD_NUM;

myfrom=tid*avgsize;
if(myfrom>=size) myend=myfrom;
myend=myfrom+avgsize;
if(tid==(THREAD_NUM-1)) myend=size;	

int p=0;	
for(int i=myfrom;i<myend;i++)
	p+=number[i];

sum[tid]=p;

// printf("%d %d\n",tid,sum[tid]);

return;

}

extern “C” void SUMP_ON_DEVICE(int* number, int* size, int* sum)
{
int* numberD;
int* sumD;

int* result;

result=(int *)malloc(sizeof(int)*THREAD_NUM);

cudaMalloc( (void **)&numberD,(*size)*sizeof(int));
cudaMalloc( (void **)&sumD,sizeof(int)*THREAD_NUM);

cudaMemcpy(numberD,number,(*size)*sizeof(int),cudaMemcpyHost

ToDevice);

sump_on_device<<<1,THREAD_NUM,0>>>(numberD,*size,sumD);

cudaMemcpy(result,sumD,THREAD_NUM*sizeof(int),cudaMemcpyDevi

ceToHost);

*sum=0;
for(int i=0;i<THREAD_NUM;i++)
	*sum+=result[i];


cudaFree(numberD);
cudaFree(sumD);
free(result);

}

int main(void)
{

int data_size=10;
int *number;

number=new int[data_size];

for(int i=0;i<data_size;i++)
{
	number[i]=i;
	printf("%d %d\n",i,number[i]);
}

int SumP_Host=0;

for(int i=0;i<data_size;i++)
	SumP_Host+=number[i];

printf("Results on host: %d \n",SumP_Host);

int SumP_Device;	
SUMP_ON_DEVICE(number, &data_size, &SumP_Device);

printf("Results on device: %d \n",SumP_Device);

delete []number;

return 0;

}

The running result on device emulation mode*
0 0
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
Results on host: 45
Results on device: 45

The running result on real GPU mode
0 0
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
Results on host: 45
Results on device: 3824584

ok.
I have found the reason.
The cuda device can not be found.

In fact, i have a Geforce 8800GT, and I have been using it for cuda programming.
But today it told me it can not be found. so my program can not run correctly

But why the device lost?

Have you tried reinstalling drivers?

Make sure you have the correct driver version installed.

Thank you all very much.
I reinstall the driver, and now it works properly.