hello_world.cu

// This is the REAL "hello world" for CUDA!
// It takes the string "Hello ", prints it, then passes it to CUDA
// with an array of offsets. Then the offsets are added in parallel
// to produce the string "World!"
// By Ingemar Ragnemalm 2010

// nvcc hello-world.cu -L /usr/local/cuda/lib -lcudart -o hello-world

#include <stdio.h>

const int N = 16; 
const int blocksize = 16; 

__global__ 
void hello(char *a, int *b) 
{
	a[threadIdx.x] += b[threadIdx.x];
}

int main()
{
	char a[N] = "Hello \0\0\0\0\0\0";
	int b[N] = {15, 10, 6, 0, -11, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

	char *ad;
	int *bd;
	const int csize = N*sizeof(char);
	const int isize = N*sizeof(int);

	printf("%s", a);

	cudaMalloc( (void**)&ad, csize ); 
	cudaMalloc( (void**)&bd, isize ); 
	cudaMemcpy( ad, a, csize, cudaMemcpyHostToDevice ); 
	cudaMemcpy( bd, b, isize, cudaMemcpyHostToDevice ); 
	
	dim3 dimBlock( blocksize, 1 );
	dim3 dimGrid( 1, 1 );
	hello<<<dimGrid, dimBlock>>>(ad, bd);
	cudaMemcpy( a, ad, csize, cudaMemcpyDeviceToHost ); 
	cudaFree( ad );
	cudaFree( bd );
	
	printf("%s\n", a);
	sleep(1);
	return EXIT_SUCCESS;
}