title: using OpenACC ,error information displays :[if not already present]
body: <p>When I compiled the code with OpenACC,I got the error information:[if not already present]</p>
  <pre><code>#include&lt;iostream&gt;
  
  #include&lt;openacc.h&gt;
  
  using namespace std;
  
  
  int main(){
  int i,j,sum=0;
  #pragma acc parallel loop copyin(i,j) copyout(sum)
  for(int i=0;i&lt;100;i++){
             #pragma acc loop
      for(int j=0;j&lt;200;j++){
             sum=i+j;
      }
  
    }
    cout&lt;&lt;sum&lt;&lt;endl;
  }
  </code></pre>
  <p>Result shows:</p>
  <blockquote>
  <p>main:</p>
  <pre><code> 8, Generating copyin(i) [if not already present]
      Generating copyout(sum) [if not already present]
      Generating copyin(j) [if not already present]
      Generating NVIDIA GPU code
     10, #pragma acc loop gang, vector(96) /* blockIdx.x &gt;threadIdx.x */
      12, #pragma acc loop seq
  13, Accelerator restriction: induction variable live-out from loop: sum
  </code></pre>
  </blockquote>
  <p>I don't quite understand why the error shows induction variable live-out from loop: sum.</p>