从device_vector中删除元素 [英] removing elements from an device_vector

问题描述

thrust :: device_vector值

thrust::device_vector values

thrust :: device_vector键;

thrust::device_vector keys;

初始化后，元素等于-1。我想删除键中值和相同位置的元素。

After initialization, keys contains some elements equal to -1. I wanted to delete the elements in keys and in the same position of values.

但我不知道如何处理它并行？

But I do not know how to deal with it parallel?

推荐答案

有很多方法可以做到这一点。一种可能的方式：

There are probably many ways to do this. One possible way:

1. 使用模板版本 thrust :: remove_if a href =http://thrust.github.io/doc/group__stream__compaction.html#ga557e8dd3130229b1a6193b3acc82ee5e =nofollow>文档），将键用作模板，删除值中的元素，其中相应的键为-1。您将需要为谓词测试创建函子。


2. 使用 thrust :: remove （文档），以删除值为-1的

1. use the stencil version of thrust::remove_if (documentation), with the keys as your stencil, removing the elements in values where the corresponding key is -1. You will need to create a functor for the predicate test.
2. use thrust::remove (documentation) on the keys to remove the values that are -1

$ b 示例：

Here's an example:

#include <iostream>
#include <thrust/device_vector.h>
#include <thrust/copy.h>
#include <thrust/remove.h>
#include <thrust/sequence.h>

#define N 12
typedef thrust::device_vector<int>::iterator dintiter;

struct is_minus_one
{
  __host__ __device__
  bool operator()(const int x)
  {
    return (x == -1);
  }
};

int main(){

  thrust::device_vector<int> keys(N);
  thrust::device_vector<int> values(N);

  thrust::sequence(keys.begin(), keys.end());
  thrust::sequence(values.begin(), values.end());

  keys[3] = -1;
  keys[9] = -1;

  dintiter nve = thrust::remove_if(values.begin(), values.end(), keys.begin(), is_minus_one());
  dintiter nke = thrust::remove(keys.begin(), keys.end(), -1);

  std::cout << "results  values:" << std::endl;
  thrust::copy(values.begin(), nve, std::ostream_iterator<int>( std::cout, " "));
  std::cout << std::endl << "results keys:" << std::endl;
  thrust::copy(keys.begin(), nke, std::ostream_iterator<int>( std::cout, " "));
  std::cout << std::endl;

  return 0;
}

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