[英]Get index of vector inside CUDA thrust::transform operator() function
In CUDA Thrust transform, is it possible to get the index of a vector, passed into the operator() function, inside the function? 在CUDA Thrust变换中,是否可以获取传递到operator()函数内的向量的索引?
say, we have, 说,我们有,
struct op{
float operator()(const float& f){
//do something like return the index
}
};
vector<float> v(100);
thrust::transform(v.begin(),v.end(),v.begin(),op());
how do i get the index of the vector inside the operator()? 如何获取operator()中向量的索引? basically i want a easy way to make a identity matrix in CUDA. 基本上我想在CUDA中制作身份矩阵的简单方法。
There are probably many ways to do this. 可能有很多方法可以做到这一点。 One approach would be: 一种方法是:
thrust::sequence
to create a vector of indices of the same length as your data vector (or instead just use a counting_iterator
) 使用thrust::sequence
创建一个索引向量,该索引的长度与数据向量的长度相同(或者只使用counting_iterator
) zip_iterator
to return a thrust::tuple
, combining the data vector and the index vector, returning a tuple of a data item plus its index 使用zip_iterator
返回thrust::tuple
,将数据向量和索引向量组合,返回数据项及其索引的元组 op()
to take the particular tuple as one of it's arguments 定义运算符op()
以将特定的元组作为其参数之一 thrust::get<>
to retrieve either the data element, or the index as needed, from the tuple 在运算符中,使用thrust::get<>
从元组中检索数据元素或索引(根据需要) You can read more about most of these concepts in the thrust quickstart guide . 您可以在推力快速入门指南中阅读更多有关这些概念的更多信息。
EDIT : In response to question below, here's a worked example. 编辑 :针对以下问题,这是一个可行的示例。 Although this doesn't actually use any device_vector
, if we were doing this on the GPU (using device_vector
) the only activity that would generate any significant GPU activity would be the call to thrust::transform
, ie. 尽管实际上并没有使用任何device_vector
,但是如果我们在GPU上执行该操作(使用device_vector
),则唯一会产生任何重要GPU活动的活动就是对thrust::transform
的调用。 there would be only 1 "pass" on the GPU. GPU上只有1次“通过”。
(Yes, the thrust::sequence call would also generate a GPU kernel, but I'm just using that to create some data for this example). (是的,推力:::序列调用也会生成一个GPU内核,但在此示例中,我只是使用它来创建一些数据)。
#include <thrust/host_vector.h>
#include <thrust/iterator/zip_iterator.h>
#include <thrust/iterator/counting_iterator.h>
#include <thrust/sequence.h>
#include <thrust/copy.h>
#define N 30
#define SELECT 3
typedef thrust::tuple<int, int> tpl2int;
typedef thrust::host_vector<int>::iterator intiter;
typedef thrust::counting_iterator<int> countiter;
typedef thrust::tuple<intiter, countiter> tpl2intiter;
typedef thrust::zip_iterator<tpl2intiter> idxzip;
struct select_unary_op : public thrust::unary_function<tpl2int, int>
{
__host__ __device__
int operator()(const tpl2int& x) const
{
if ((x.get<1>() %SELECT) == 0)
return x.get<0>();
else return -1;
}
};
int main() {
thrust::host_vector<int> A(N);
thrust::host_vector<int> result(N);
thrust::sequence(A.begin(), A.end());
thrust::counting_iterator<int> idxfirst(0);
thrust::counting_iterator<int> idxlast = idxfirst +N;
idxzip first = thrust::make_zip_iterator(thrust::make_tuple(A.begin(), idxfirst));
idxzip last = thrust::make_zip_iterator(thrust::make_tuple(A.end(), idxlast));
select_unary_op my_unary_op;
thrust::transform(first, last, result.begin(), my_unary_op);
std::cout << "Results :" << std::endl;
thrust::copy(result.begin(), result.end(), std::ostream_iterator<int>( std::cout, " "));
std::cout << std::endl;
return 0;
}
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