Template Function thrust::exclusive_scan_by_key(InputIterator1, InputIterator1, InputIterator2, OutputIterator)

Function Documentation

template<typename InputIterator1, typename InputIterator2, typename OutputIterator>
OutputIterator thrust::exclusive_scan_by_key(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, OutputIterator result)

exclusive_scan_by_key computes an exclusive segmented prefix

This version of exclusive_scan_by_key uses the value 0 to initialize the exclusive scan operation.

This version of exclusive_scan_by_key assumes plus as the associative operator used to perform the prefix sum. When the input and output sequences are the same, the scan is performed in-place.

This version of exclusive_scan_by_key assumes equal_to as the binary predicate used to compare adjacent keys. Specifically, consecutive iterators i and i+1 in the range [first1, last1 belong to the same segment if *i == *(i+1), and belong to different segments otherwise.

Refer to the most general form of exclusive_scan_by_key for additional details.

The following code snippet demonstrates how to use

exclusive_scan_by_key.
Pre

first1 may equal result but the range [first1, last1) and the range [result, result + (last1 - first1)) shall not overlap otherwise.

Pre

first2 may equal result but the range [first2, first2 + (last1 - first1) and range [result, result + (last1 - first1)) shall not overlap otherwise.

Parameters

  • first1: The beginning of the key sequence.

  • last1: The end of the key sequence.

  • first2: The beginning of the input value sequence.

  • result: The beginning of the output value sequence.

#include <thrust/scan.h>

int keys[10] = {0, 0, 0, 1, 1, 2, 3, 3, 3, 3};
int vals[10] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1};

thrust::exclusive_scan_by_key(key, key + 10, vals, vals); // in-place scan

// vals is now {0, 1, 2, 0, 1, 0, 0, 1, 2, 3};

See

exclusive_scan