CUDA推力zip_iterator元组transform_reduce [英] CUDA thrust zip_iterator tuple transform_reduce

问题描述

我想计算 和，其中表示向量的大小。因为这涉及取两个向量的每个相应分量之间的差的平方和的平方根，所以它应当是高度可并行化的任务。我使用Cuda和Thrust，通过Cygwin，在Windows 10上。Cuda和Thrust一般都工作。

I want to compute for vectors and , where denotes the magnitude of the vector . Since this involves taking the square root of the sum of the squares of the differences between each corresponding component of the two vectors, it should be a highly parallelizable task. I am using Cuda and Thrust, through Cygwin, on Windows 10. Both Cuda and Thrust are in general working.

下面的代码编译和运行（使用nvcc），但是只是因为我已经注释掉了三行朝向 main 的底部，每个我认为应该工作，但不是。 func :: operator（）（tup t）认为我传递的参数实际上不是类型tup。

The below code compiles and runs (with nvcc), but only because I have commented out three lines toward the bottom of main, each of which I think should work but does not. func::operator()(tup t) thinks that the arguments I'm passing it are not in fact of type tup.

我也注释掉了操作符的实际主体，以便更有可能至少编译。运算符应该找到输入tup的元素之间的平方差。减少 unary_op 从 transform_reduce （在本例中为 func（））然后将添加这些，给我的向量的差异的范数平方。

I have also commented out the actual body of the operator, in the interest of making it more likely to at least compile. The operator is supposed to find the squared difference between the elements of the input tup. The reduction unary_op from transform_reduce (which in this case is func()) would then add these, giving me the norm squared of the difference of vectors.

#include <iostream>
#include <stdlib.h>
#include <thrust/device_vector.h>
#include <thrust/transform.h>
#include <thrust/tuple.h>
#include <thrust/transform_reduce.h>
#include <thrust/iterator/zip_iterator.h>

typedef thrust::device_vector<float> dvec;
typedef dvec::iterator iter;
typedef thrust::tuple<iter, iter> tup;

struct func: public thrust::unary_function<tup, float>
{
  __device__ float operator()(tup t) //difsq
  {
    // I've commented out these two lines for testing purposes:
    // float f = thrust::get<0>(t) - thrust::get<1>(t);
    // return f*f;
    return 3.14;
  }
};

int main()
{
  dvec a(40, 4.f);
  dvec b(40, 3.f);
  auto begin = thrust::make_zip_iterator(thrust::make_tuple(a.begin(), b.begin()));
  auto end = thrust::make_zip_iterator(thrust::make_tuple(a.end(), b.end()));

  //these two lines work
  thrust::get<0>(begin[0]);
  std::cout << thrust::get<0>(begin[0]) - thrust::get<1>(begin[0]);


  //these three lines do not
  //thrust::transform_reduce(begin, end, func(), 0.0f, thrust::plus<float>());
  //func()(begin[0]);
  //thrust::transform(begin, end, begin, func());


  std::cout << "done" << std::endl;
  return 0;
}

我得到这个错误:(我的程序叫 sandbox.cu ）

I get this error: (my program is called sandbox.cu)

C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v7.5\bin/../include\thrust/detail/tuple.inl(310): error: no instance of constructor "thrust::detail::normal_iterator<Pointer>::normal_iterator [with Pointer=thrust::device_ptr<float>]" matches the argument list
        argument types are: (const thrust::device_reference<float>)
      detected during:
        instantiation of "thrust::detail::cons<HT, TT>::cons(const thrust::detail::cons<HT2, TT2> &) [with HT=iter, TT=thrust::detail::cons<iter, thrust::null_type>, HT2=thrust::device_reference<float>, TT2=thrust::detail::cons<thrust::device_reference<float>, thrust::null_type>]"
C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v7.5\bin/../include\thrust/tuple.h(361): here
        instantiation of "thrust::tuple<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>::tuple(const thrust::detail::cons<U1, U2> &) [with T0=iter, T1=iter, T2=thrust::null_type, T3=thrust::null_type, T4=thrust::null_type, T5=thrust::null_type, T6=thrust::null_type, T7=thrust::null_type, T8=thrust::null_type, T9=thrust::null_type, U1=thrust::device_reference<float>, U2=thrust::detail::cons<thrust::device_reference<float>, thrust::null_type>]"
sandbox.cu(37): here

C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v7.5\bin/../include\thrust/detail/tuple.inl(411): error: no instance of constructor "thrust::detail::normal_iterator<Pointer>::normal_iterator [with Pointer=thrust::device_ptr<float>]" matches the argument list
            argument types are: (const thrust::device_reference<float>)
          detected during:
            instantiation of "thrust::detail::cons<HT, thrust::null_type>::cons(const thrust::detail::cons<HT2, thrust::null_type> &) [with HT=iter, HT2=thrust::device_reference<float>]"
(310): here
            instantiation of "thrust::detail::cons<HT, TT>::cons(const thrust::detail::cons<HT2, TT2> &) [with HT=iter, TT=thrust::detail::cons<iter, thrust::null_type>, HT2=thrust::device_reference<float>, TT2=thrust::detail::cons<thrust::device_reference<float>, thrust::null_type>]"
C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v7.5\bin/../include\thrust/tuple.h(361): here
            instantiation of "thrust::tuple<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9>::tuple(const thrust::detail::cons<U1, U2> &) [with T0=iter, T1=iter, T2=thrust::null_type, T3=thrust::null_type, T4=thrust::null_type, T5=thrust::null_type, T6=thrust::null_type, T7=thrust::null_type, T8=thrust::null_type, T9=thrust::null_type, U1=thrust::device_reference<float>, U2=thrust::detail::cons<thrust::device_reference<float>, thrust::null_type>]"
sandbox.cu(37): here

2 errors detected in the compilation of "C:/cygwin64/tmp/tmpxft_00001a90_00000000-10_sandbox.cpp1.ii".

推荐答案

tup 应该是 thrust :: tuple< float，float> ，而不是 thrust :: tuple< iter，iter> 。完整解决方案：

Solved! tup should have been thrust::tuple<float, float>, not thrust::tuple<iter, iter>. Full solution:

#include <iostream>
#include <stdlib.h>
#include <thrust/device_vector.h>
#include <thrust/transform.h>
#include <thrust/tuple.h>
#include <thrust/transform_reduce.h>
#include <thrust/iterator/zip_iterator.h>

typedef thrust::device_vector<float> dvec;
typedef thrust::tuple<float, float> tup;

struct func
{
  __device__ float operator()(tup t) //difsq
  {
     float f = thrust::get<0>(t) - thrust::get<1>(t);
     return f*f;
  }
};

int main()
{
  dvec a(4, 3.f);
  dvec b(4, 2.f);
  auto begin = thrust::make_zip_iterator(thrust::make_tuple(a.begin(), b.begin()));
  auto end = thrust::make_zip_iterator(thrust::make_tuple(a.end(), b.end()));
  std::cout << thrust::transform_reduce(begin, end, func(), 0.0f, thrust::plus<float>()) << std::endl;
  std::cout << "done" << std::endl;
  return 0;
}

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