error: no viable conversion from 'std::array<int, n>' to 'const void *' using SYCL/DPC++

Question

我是 SYCL/DPC++ 的初学者。我使用 USM（统一共享内存）编写了代码，并采用了两个数组主机和设备数组，我想在其中将主机数组值复制到设备数组并执行基本操作并打印值。但是在编译的时候，报错了。

这是我的代码。

#include <CL/sycl.hpp>
#include <array>
#include<iostream>
using namespace std;
using namespace sycl;
const int n = 6;

int main() {
  queue q;

  std::array<int,n> h_a;
  int *d_a = malloc_device<int>(n, q);
  for (int i = 0; i < n; i++)
    h_a[i] = n;

  q.submit([&](handler& h) {
      h.memcpy(d_a,h_a,n * sizeof(int));
    });
  q.wait();

  q.submit([&](handler& h) {
      h.parallel_for(n, [=](id<1> i) {
          d_a[i] = d_a[i] * 2;
          d_a[i] = d_a[i] + 2;
          d_a[i] = d_a[i] - 2;
          d_a[i] = d_a[i] + 2;
        });
    });
  q.wait();

  q.submit([&](handler& h) {
      h.memcpy(h_a,d_a,n * sizeof(int));
    });
  q.wait();
  for(int i = 0;i < n;i++){
    cout<<h_a[i]<<" "<<d_a[i]<<" ";
  }
  cout<<"\n";

  free(d_a, q);
  return 0;
}

编译错误

simpleope.cpp:17:20: error: no viable conversion from 'std::array<int, n>' to 'const void *'
      h.memcpy(d_a,h_a,n * sizeof(int));
                   
/opt/intel/oneapi/compiler/2021.3.0/linux/bin/../include/sycl/CL/sycl/handler.hpp:2171:39: note: passing argument to parameter 'Src' here
  void memcpy(void *Dest, const void *Src, size_t Count);
                                      
simpleope.cpp:32:16: error: no viable conversion from 'std::array<int, n>' to 'void *'
      h.memcpy(h_a,d_a,n * sizeof(int));
               
/opt/intel/oneapi/compiler/2021.3.0/linux/bin/../include/sycl/CL/sycl/handler.hpp:2171:21: note: passing argument to parameter 'Dest' here
  void memcpy(void *Dest, const void *Src, size_t Count);
                    
2 errors generated.

谁能帮我看看哪里出错了？

提前致谢。

Answer 1

memcpy() 的语法是

`void memcpy(void *Dest, const void *Src, size_t Count);`

您需要通过引用传递而不是值传递来传递第二个参数。您可以将 &h_a（或）&h_a[0]（或）h_a.data() 中的任何一个作为参数传递，以消除代码中的这些错误。修改后的代码为

#include <CL/sycl.hpp>
#include <array>
#include<iostream>
using namespace std;
using namespace sycl;
const int n = 6; int main() {
  queue q;   std::array<int,n> h_a;
  int *d_a = malloc_device<int>(n, q);
  for (int i = 0; i < n; i++)
    h_a[i] = n;   
q.submit([&](handler& h) {
      h.memcpy(d_a,&h_a,n * sizeof(int));
    });
  q.wait();   
q.submit([&](handler& h) {
      h.parallel_for(n, [=](id<1> i) {
          d_a[i] = d_a[i] * 2;
          d_a[i] = d_a[i] + 2;
          d_a[i] = d_a[i] - 2;
          d_a[i] = d_a[i] + 2;
        });
    });

  q.wait();   
q.submit([&](handler& h) {
      h.memcpy(&h_a,d_a,n * sizeof(int));
    });
  q.wait();
  for(int i = 0;i < n;i++){
    cout<<h_a[i]<<" "<<d_a[i]<<" ";
  }
  cout<<"\n";   free(d_a, q);
  return 0;
}

error: no viable conversion from 'std::array<int, n>' to 'const void *' using SYCL/DPC++

error: no viable conversion from 'std::array<int, n>' to 'const void *' using SYCL/DPC++

c++

parallel-processing

sycl

intel-oneapi

dpc++