Template Function thrust::inclusive_scan(InputIterator, InputIterator, OutputIterator)

Function Documentation

template<typename InputIterator, typename OutputIterator>
OutputIterator thrust::inclusive_scan(InputIterator first, InputIterator last, OutputIterator result)

inclusive_scan computes an inclusive prefix sum operation. The term ‘inclusive’ means that each result includes the corresponding input operand in the partial sum. More precisely, *first is assigned to *result and the sum of *first and *(first + 1) is assigned to *(result + 1), and so on. This version of inclusive_scan assumes plus as the associative operator. When the input and output sequences are the same, the scan is performed in-place.

inclusive_scan is similar to std::partial_sum in the STL. The primary difference between the two functions is that std::partial_sum guarantees a serial summation order, while inclusive_scan requires associativity of the binary operation to parallelize the prefix sum.

The following code snippet demonstrates how to use

inclusive_scan
Return

The end of the output sequence.

Pre

first may equal result but the range [first, last) and the range [result, result + (last - first)) shall not overlap otherwise.

Parameters

  • first: The beginning of the input sequence.

  • last: The end of the input sequence.

  • result: The beginning of the output sequence.

Template Parameters

  • InputIterator: is a model of Input Iterator and InputIterator's value_type is convertible to OutputIterator's value_type.

  • OutputIterator: is a model of Output Iterator, and if x and y are objects of OutputIterator's value_type, then x + y is defined. If T is OutputIterator's value_type, then T(0) is defined.

#include <thrust/scan.h>

int data[6] = {1, 0, 2, 2, 1, 3};

thrust::inclusive_scan(data, data + 6, data); // in-place scan

// data is now {1, 1, 3, 5, 6, 9}

See

http://www.sgi.com/tech/stl/partial_sum.html