推力减小结果在设备存储器 [英] thrust reduction result on device memory

问题描述

是否可以在设备分配的内存中保留thrust :: reduce操作的返回值？如果是，是否就像将值分配给cudaMalloc区域一样简单，或者应该使用thrust :: device_ptr？

Is it possible to leave the return value of a thrust::reduce operation in device-allocated memory? In case it is, is it just as easy as assigning the value to a cudaMalloc'ed area, or should I use a thrust::device_ptr?

推荐答案

是否可以在设备分配的内存中保留thrust :: reduce操作的返回值？

Is it possible to leave the return value of a thrust::reduce operation in device-allocated memory?

简短的答案是否定的。

thrust减少返回一个数量，减少的结果。此数量必须存储在主机常驻变量中：

thrust reduce returns a quantity, the result of the reduction. This quantity must be deposited in a host resident variable:

例如，reduce是同步的，
总是将结果返回给CPU：

Take for example reduce, which is synchronous and always returns its result to the CPU:

template<typename Iterator, typename T> 
T reduce(Iterator first, Iterator last, T init); 

一旦操作结果返回到CPU，就可以将其复制到GPU if您喜欢：

Once the result of the operation has been returned to the CPU, you can copy it to the GPU if you like:

#include <iostream>
#include <thrust/device_vector.h>
#include <thrust/reduce.h>

int main(){

    thrust::device_vector<int> data(256, 1);
    thrust::device_vector<int> result(1);
    result[0] = thrust::reduce(data.begin(), data.end());
    std::cout << "result = " << result[0] << std::endl;
    return 0;
}

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