HBeonGpgpu

Hello world on a GPU is quite interesting as generally people dop not work on character processing on GPUs. The foillowing code is an example :          

/*

** Hello World using CUDA

**

** The string "Hello World!" is mangled then restored using a common CUDA idiom

**

** Byron Galbraith

** 2009-02-18

*/

#include <cuda.h>

#include <stdio.h>

// Prototypes

__global__ void helloWorld(char*);

// Host function

int

main(int argc, char** argv)

{

int i;

// desired output

char str[] = "Hello World!";

// mangle contents of output

// the null character is left intact for simplicity

for(i = 0; i < 12; i++)

str[i] -= i;

// allocate memory on the device

char *d_str;

size_t size = sizeof(str);

cudaMalloc((void**)&d_str, size);

// copy the string to the device

cudaMemcpy(d_str, str, size, cudaMemcpyHostToDevice);

// set the grid and block sizes

dim3 dimGrid(2); // one block per word

dim3 dimBlock(6); // one thread per character

// invoke the kernel

helloWorld<<< dimGrid, dimBlock >>>(d_str);

// retrieve the results from the device

cudaMemcpy(str, d_str, size, cudaMemcpyDeviceToHost);

// free up the allocated memory on the device

cudaFree(d_str);

// everyone's favorite part

printf("%s\n", str);

return 0;

}

// Device kernel

__global__ void

helloWorld(char* str)

{

// determine where in the thread grid we are

int idx = blockIdx.x * blockDim.x + threadIdx.x;

// unmangle output

str[idx] += idx;

}

Have a look at this for more detail:

http://forums.nvidia`.com/index.php?showtopic=90044