推力::序列 - 如何在每个 N 个元素之后增加步长 [英] thrust::sequence - how to increase the step after each N elements

问题描述

我正在使用

thrust::sequence(myvector.begin(), myvector.end(), 0, 1)

并获得良好的有序列表，例如:

and achieve good ordered list like:

0, 1, 2, 3, 4

我的问题是如何实现下面的这样一个列表(最好的方法?)

My question is how can I achieve such a list below (the best way?)

0, 0, 0, 1, 1, 1, 2, 2 ,2, 3, 3, 3

我知道怎么用函子来做，所以请不要试图用函子来回答.我想了解在 Thrust 中是否有针对它的优化方法，或者我是否缺少一种简单的方法..

I know how to make it with functors, so please do not try to answer it with functor. I want to learn if there is an optimized way for it in Thrust, or am I missing a simple way..

推荐答案

类似这样的:

thrust::device_vector<int> myvector(N);

thrust::transform( thrust::make_counting_iterator(0),
                   thrust::make_counting_iterator(N),
                   thrust::make_constant_iterator(3),
                   myvector.begin(),
                   thrust::divides<int>() );

(免责声明，用浏览器编写，从未编译或测试过，使用风险自负)

(disclaimer, written in browser, never compiled or tested, use at own risk)

应该通过计算 [0..N]//3 并在 myvector 上输出结果来为您提供您正在寻找的序列.

should give you the sequence you are looking for by computing [0..N]//3 and outputting the result on myvector.

鉴于您在编译版本时遇到问题，这里有一个完整的编译和运行示例:

Seeing as you are having trouble compiling your version, here is a complete example which compiles and runs:

#include <thrust/device_vector.h>
#include <thrust/transform.h>
#include <thrust/functional.h>
#include <thrust/iterator/counting_iterator.h>
#include <thrust/iterator/constant_iterator.h>
#include <cstdio>

int main(void)
{
    const int N = 18, M = 3;
    thrust::device_vector<int> myvector(N);

    thrust::transform(  thrust::make_counting_iterator(0),
                        thrust::make_counting_iterator(N),
                        thrust::make_constant_iterator(M),
                        myvector.begin(),
                        thrust::divides<int>() );

    for(int i=0; i<N; i++) {
        int val = myvector[i];
        printf("%d %d
", i, val);
    }
    return 0;
}

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