Cuda Thrust Custom function

Question

How can I impliment this function in Thrust?

for (i=0;i

Answer 1

You need to create a binary functor to apply the operation, then use a counting iterator as the second input. You can pass pos and value into the functor's constructor. It'd look something like:

struct inv1_functor
{
  const int pos;
  const double value;

  inv1_functor(double _value, int _pos) : value(_value), pos(_pos) {}

  __host__ __device__
  double operator()(const double &x, const int &i) const {
    if (i == pos)
      return 1.0/x;
    else
      return -x/value;
  }
};

//...

thrust::transform(d_vec.begin(), d_vec.end(), thrust::counting_iterator<int>(),  d_vec.begin(), inv1_functor(value, pos));