CUDA推拉zip_iterator元组transform_reduce

Question

我想为向量和计算，其中表示向量的大小。由于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，因此它应该是高度可并行化的任务。我在Windows 10上使用Cuda和Thrust，通过Cygwin .Cuda和Thrust都在工作。

下面的代码编译并运行（使用nvcc），但这只是因为我在main的底部注释了三行，我认为每行都应该有效但不行。 func::operator()(tup t)认为我传递的参数实际上并不是tup类型。

为了使其更有可能至少编译，我还注释了运算符的实际主体。运算符应该找到输入tup的元素之间的平方差异。来自unary_op的减少transform_reduce（在这种情况下为func()）将添加这些，给出了向量差异的范数平方。

#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;
}

我收到此错误:(我的程序名为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".

Answer 1

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

#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;
}