thrust::constant_iterator#

template<typename Value, typename Incrementable = use_default, typename System = use_default> class constant_iterator : public thrust::iterator_adaptor<constant_iterator<Value, use_default, use_default>, base_iterator, Value, iterator_system_t<base_iterator>, iterator_traversal_t<base_iterator>, Value>#

constant_iterator is an iterator which represents a pointer into a range of constant values.

This iterator is useful for creating a range filled with the same value without explicitly storing it in memory. Using constant_iterator saves both memory capacity and bandwidth.

The following code snippet demonstrates how to create a constant_iterator whose value_type is int and whose value is 10.

#include <thrust/iterator/constant_iterator.h>

thrust::constant_iterator<int> iter(10);

*iter;    // returns 10
iter[0];  // returns 10
iter[1];  // returns 10
iter[13]; // returns 10

// and so on...

This next example demonstrates how to use a constant_iterator with the thrust::transform function to increment all elements of a sequence by the same value. We will create a temporary constant_iterator with the function make_constant_iterator function in order to avoid explicitly specifying its type:

#include <thrust/iterator/constant_iterator.h>
#include <thrust/transform.h>
#include <thrust/functional.h>
#include <thrust/device_vector.h>

int main()
{
  thrust::device_vector<int> data{3, 7, 2, 5};

  // add 10 to all values in data
  thrust::transform(data.begin(), data.end(),
                    thrust::make_constant_iterator(10),
                    data.begin(),
                    ::cuda::std::plus<int>());

  // data is now [13, 17, 12, 15]

  return 0;
}