Template Function thrust::exclusive_scan(InputIterator, InputIterator, OutputIterator, T, AssociativeOperator)

Function Documentation

template<typename InputIterator, typename OutputIterator, typename T, typename AssociativeOperator>
OutputIterator thrust::exclusive_scan(InputIterator first, InputIterator last, OutputIterator result, T init, AssociativeOperator binary_op)

exclusive_scan computes an exclusive prefix sum operation. The term ‘exclusive’ means that each result does not include the corresponding input operand in the partial sum. More precisely, init is assigned to *result and the value binary_op(init, *first) is assigned to *(result + 1), and so on. This version of the function requires both an associative operator and an initial value init. When the input and output sequences are the same, the scan is performed in-place.

The following code snippet demonstrates how to use

exclusive_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.

  • init: The initial value.

  • binary_op: The associatve operator used to ‘sum’ values.

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 OutputIterator's value_type is convertible to both AssociativeOperator's first_argument_type and second_argument_type.

  • T: is convertible to OutputIterator's value_type.

  • AssociativeOperator: is a model of Binary Function and AssociativeOperator's result_type is convertible to OutputIterator's value_type.

#include <thrust/scan.h>
#include <thrust/functional.h>

int data[10] = {-5, 0, 2, -3, 2, 4, 0, -1, 2, 8};

thrust::maximum<int> binary_op;

thrust::exclusive_scan(data, data + 10, data, 1, binary_op); // in-place scan

// data is now {1, 1, 1, 2, 2, 2, 4, 4, 4, 4 }

See

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