将char数组传递给CUDA内核

Question

I am trying to pass an char array containing 10000 words read from a txt file in the main function to CUDA kernel function.

The words are transferred from the host to device like this:

(main function code:)

//.....
     const int text_length = 20;

     char (*wordList)[text_length] = new char[10000][text_length];
     char *dev_wordList;

     for(int i=0; i<number_of_words; i++)
     {
         file>>wordList[i];
         cout<<wordList[i]<<endl;
     }

     cudaMalloc((void**)&dev_wordList, 20*number_of_words*sizeof(char));
     cudaMemcpy(dev_wordList, &(wordList[0][0]), 20 * number_of_words * sizeof(char), cudaMemcpyHostToDevice);

    //Setup execution parameters
    int n_blocks = (number_of_words + 255)/256;
    int threads_per_block = 256;


    dim3 grid(n_blocks, 1, 1);
    dim3 threads(threads_per_block, 1, 1);


    cudaPrintfInit();
    testKernel<<<grid, threads>>>(dev_wordList);
    cudaDeviceSynchronize();
    cudaPrintfDisplay(stdout,true);
    cudaPrintfEnd();

(kernel function code:)

__global__ void testKernel(char* d_wordList)
{
    //access thread id
    const unsigned int bid = blockIdx.x;
    const unsigned int tid = threadIdx.x;
    const unsigned int index = bid * blockDim.x + tid;

    cuPrintf("!! %c%c%c%c%c%c%c%c%c%c \n" , d_wordList[index * 20 + 0],
                                            d_wordList[index * 20 + 1],
                                            d_wordList[index * 20 + 2],
                                            d_wordList[index * 20 + 3],
                                            d_wordList[index * 20 + 4],
                                            d_wordList[index * 20 + 5],
                                            d_wordList[index * 20 + 6],
                                            d_wordList[index * 20 + 7],
                                            d_wordList[index * 20 + 8],
                                            d_wordList[index * 20 + 9]);
}

Is there a way to manipulate them easier? (I would like to have a word per element/position) I tried with <string> , but I can't use them in CUDA device code.

Answer 1

cuPrintf("%s\n", d_wordlist+(index*20));

should work? (provided your strings are zero-terminated)

Update:

This line:

char (*wordList)[text_length] = new char[10000][text_length];

looks strange to me. In general, array of pointers to char would be allocated like this:

char** wordList = new char*[10000];
for (int i=0;i<10000;i++) wordList[i] = new char[20];

In this case, wordList[i] would be a pointer to string number i.

Update #2:

If you need to store your strings as a consecutive block, and you are sure that none of your strings exceeds text_length+1, then you can do like that:

char *wordList = new char[10000*text_length];

for(int i=0; i<number_of_words; i++)
     {
         file>>wordList+(i*text_length);
         cout<<wordList+(i*text_length)<<endl;
     }

In that case, wordList + (i*text_length) will point to the beginning of your string number i, and it will be 0-terminated because that's how you read it from the file, and you will be able to print it out with the way specified in this answer. If any of your strings is longer than text_length-1, however, you will still get issues.