Cuda 内核返回向量 [英] Cuda kernel returning vectors

问题描述

我有一个单词列表，我的目标是匹配一个非常长的短语中的每个单词.我在匹配每个单词时没有问题，我唯一的问题是返回一个包含每个匹配信息的结构向量.

I have a list of words, my goal is to match each word in a very very long phrase. I'm having no problem in matching each word, my only problem is to return a vector of structures containing informations about each match.

在代码中:

typedef struct {
    int A, B, C; } Match;

__global__ void Find(veryLongPhrase * _phrase, Words * _word_list, vector<Match> * _matches)
{
    int a, b, c;

    [...] //Parallel search for each word in the phrase

    if(match) //When an occurrence is found
    {
        _matches.push_back(new Match{ A = a, B = b, C = c }); //Here comes the unknown, what should I do here???
    }
}

main()
{
    [...]

    veryLongPhrase * myPhrase = "The quick brown fox jumps over the lazy dog etc etc etc..."

    Words * wordList = {"the", "lazy"};

    vector<Match> * matches; //Obviously I can't pass a vector to a kernel

    Find<<< X, Y >>>(myPhrase, wordList, matches);

    [...]

}

我已经尝试过 Thrust 库，但没有成功，你能给我建议任何类型的解决方案吗?

I have tried Thrust library but without any success, can you suggest me any kind of solution?

非常感谢.

推荐答案

这样的事情应该可以工作(在浏览器中编码，未测试):

something like this should work (coded in browser, not tested):

// N is the maximum number of structs to insert
#define N 10000

typedef struct {
    int A, B, C; } Match;

__device__ Match dev_data[N];
__device__ int dev_count = 0;

__device__ int my_push_back(Match * mt) {
  int insert_pt = atomicAdd(&dev_count, 1);
  if (insert_pt < N){
    dev_data[insert_pt] = *mt;
    return insert_pt;}
  else return -1;}

__global__ void Find(veryLongPhrase * _phrase, Words * _word_list, vector<Match> * _matches)
{
    int a, b, c;

    [...] //Parallel search for each word in the phrase

    if(match) //When an occurrence is found
    {
        my_push_back(new Match{ A = a, B = b, C = c });    }
}


main()
{
    [...]

    veryLongPhrase * myPhrase = "The quick brown fox jumps over the lazy dog etc etc etc..."

    Words * wordList = {"the", "lazy"};

    Find<<< X, Y >>>(myPhrase, wordList);

    int dsize;
    cudaMemcpyFromSymbol(&dsize, dev_count, sizeof(int));
    vector<Match> results(dsize);
    cudaMemcpyFromSymbol(&(results[0]), dev_data, dsize*sizeof(Match));

    [...]

}

这将需要原子操作的计算能力 1.1 或更高.

This will require compute capability 1.1 or better for the atomic operation.

nvcc -arch=sm_11 ...

这是一个有效的例子:

$ cat t347.cu
#include <iostream>
#include <vector>

// N is the maximum number of structs to insert
#define N 10000

typedef struct {
    int A, B, C; } Match;

__device__ Match dev_data[N];
__device__ int dev_count = 0;

__device__ int my_push_back(Match & mt) {
  int insert_pt = atomicAdd(&dev_count, 1);
  if (insert_pt < N){
    dev_data[insert_pt] = mt;
    return insert_pt;}
  else return -1;}

__global__ void Find()
{

    if(threadIdx.x < 10) //Simulate a found occurrence
    {
        Match a = { .A = 1, .B = 2, .C = 3 };
        my_push_back(a);    }
}


main()
{

    Find<<< 2, 256 >>>();

    int dsize;
    cudaMemcpyFromSymbol(&dsize, dev_count, sizeof(int));
    if (dsize >= N) {printf("overflow error
"); return 1;}
    std::vector<Match> results(dsize);
    cudaMemcpyFromSymbol(&(results[0]), dev_data, dsize*sizeof(Match));
    std::cout << "number of matches = " << dsize << std::endl;
    std::cout << "A  =  " << results[dsize-1].A << std:: endl;
    std::cout << "B  =  " << results[dsize-1].B << std:: endl;
    std::cout << "C  =  " << results[dsize-1].C << std:: endl;

}
$ nvcc -arch=sm_11 -o t347 t347.cu
$ ./t347
number of matches = 20
A  =  1
B  =  2
C  =  3
$

注意，在这种情况下，我的Match结果结构创建是不同的，我是通过引用传递的，但概念是一样的.

Note that in this case my Match result struct creation is different, and I am passing by reference, but the concept is the same.

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