OpenACC - Start

OpenACC: Quick reference, home page, tutorial (Dr.Dobb's)

The compilers by PGI have to be used, see trial version. Release information.
C++ classes:  by Rob Farber, PGI 14.4, PGI notes §2.6.4,

Compiling Code:

How to OpenACC parallelize the inner product:

Original code for inner product: 
double scalar(const int N, const double x[], const double y[])
{
 double sum = 0.0;
 for (int i=0; i<N; ++i)
 {
    sum += x[i]*y[i];
 }
 return sum;
}

int main()
{
  ...
  double s = scalar(n,a,b);
  ... 
}


OpenACC code for inner product: 
// local sequential inner product
double scalar(const int N, const double x[], const double y[])
{
 double sum = 0.0;
#pragma acc kernels loop present_or_copyin(x[0:N], y[0:N]) independent reduction(+:sum)
 for (int i=0; i<N; ++i)   
     sum += x[i]*y[i];
 return sum;
}

int main(int argc, char* argv[])
{
  ...

  #pragma acc data copyin(a[0:nnode],b[0:nnode])
  {
    ...
    double s = scalar(n,a,b);
    ...
  }
  ...
}

and  compile the code with one of the available compilers