CUDA Programming: Compilation Error - linux

Question

I am making a CUDA program that implements the data parallel prefix sum calculation operating upon N numbers. My code is also supposed to generate the numbers on the host using a random number generator. However, I seem to always run into a "unrecognized token" and "expected a declaration" error on the ending bracket of int main when attempting to compile. I am running the code on Linux.
#include <stdio.h>
#include <cuda.h>
#include <stdlib.h>
#include <math.h>
__global__ void gpu_cal(int *a,int i, int n) {
int tid = blockIdx.x * blockDim.x + threadIdx.x;
if(tid>=i && tid < n) {
a[tid] = a[tid]+a[tid-i];
}
}
int main(void)
{
int key;
int *dev_a;
int N=10;//size of 1D array
int B=1;//blocks in the grid
int T=10;//threads in a block
do{
printf ("Some limitations:\n");
printf (" Maximum number of threads per block = 1024\n");
printf (" Maximum sizes of x-dimension of thread block = 1024\n");
printf (" Maximum size of each dimension of grid of thread blocks = 65535\n");
printf (" N<=B*T\n");
do{
printf("Enter size of array in one dimension, currently %d\n",N);
scanf("%d",&N);
printf("Enter size of blocks in the grid, currently %d\n",B);
scanf("%d",&B);
printf("Enter size of threads in a block, currently %d\n",T);
scanf("%d",&T);
if(N>B*T)
printf("N>B*T, this will result in an incorrect result generated by GPU, please try again\n");
if(T>1024)
printf("T>1024, this will result in an incorrect result generated by GPU, please try again\n");
}while((N>B*T)||(T>1024));
cudaEvent_t start, stop; // using cuda events to measure time
float elapsed_time_ms1, elapsed_time_ms3;
int a[N],gpu_result[N];//for result generated by GPU
int cpu_result[N];//CPU result
cudaMalloc((void**)&dev_a,N * sizeof(int));//allocate memory on GPU
int i,j;
srand(1); //initialize random number generator
for (i=0; i < N; i++) // load array with some numbers
a[i] = (int)rand() ;
cudaMemcpy(dev_a, a , N*sizeof(int),cudaMemcpyHostToDevice);//load data from host to device
cudaEventCreate(&start); // instrument code to measure start time
cudaEventCreate(&stop);
cudaEventRecord(start, 0);
//GPU computation
for(j=0;j<log(N)/log(2);j++){
gpu_cal<<<B,T>>>(dev_a,pow(2,j),N);
cudaThreadSynchronize();
}
cudaMemcpy(gpu_result,dev_a,N*sizeof(int),cudaMemcpyDeviceToHost);
cudaEventRecord(stop, 0); // instrument code to measue end time
cudaEventSynchronize(stop);
cudaEventElapsedTime(&elapsed_time_ms1, start, stop );
printf("\n\n\nTime to calculate results on GPU: %f ms.\n", elapsed_time_ms1); // print out execution time
//CPU computation
cudaEventRecord(start, 0);
for(i=0;i<N;i++)
{
cpu_result[i]=0;
for(j=0;j<=i;j++)
{
cpu_result[i]=cpu_result[i]+a[j];
}
}
cudaEventRecord(stop, 0); // instrument code to measue end time
cudaEventSynchronize(stop);
cudaEventElapsedTime(&elapsed_time_ms3, start, stop );
printf("Time to calculate results on CPU: %f ms.\n\n", elapsed_time_ms3); // print out execution time
//Error check
for(i=0;i < N;i++) {
if (gpu_result[i] != cpu_result[i] ) {
printf("ERROR!!! CPU and GPU create different answers\n");
break;
}
}
//Calculate speedup
printf("Speedup on GPU compared to CPU= %f\n", (float) elapsed_time_ms3 / (float) elapsed_time_ms1);
printf("\nN=%d",N);
printf("\nB=%d",B);
printf("\nT=%d",T);
printf("\n\n\nEnter '1' to repeat, or other integer to terminate\n");
scanf("%d",&key);
}while(key == 1);
cudaFree(dev_a);//deallocation
return 0;
}​

Answer 1

The very last } in your code is a Unicode character. If you delete this entire line, and retype the }, the error will be gone.

Answer 2

There are two compile errors in your code.
First, Last ending bracket is a unicode character, so you should resave your code as unicode or delete and rewrite the last ending bracket.
Second, int type variable N which used at this line - int a[N],gpu_result[N];//for result generated by GPU
was declared int type, but it's not allowed in c or c++ compiler, so you should change the N declaration as const int N.