Thrust

◆ exclusive_scan() [2/6]

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

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, 0 is assigned to *result and the sum of 0 and *first is assigned to *(result + 1), and so on. This version of exclusive_scan assumes plus as the associative operator and 0 as the initial value. When the input and output sequences are the same, the scan is performed in-place.

Results are not deterministic for pseudo-associative operators (e.g., addition of floating-point types). Results for pseudo-associative operators may vary from run to run.

Parameters
firstThe beginning of the input sequence.
lastThe end of the input sequence.
resultThe beginning of the output sequence.
Returns
The end of the output sequence.
Template Parameters
InputIteratoris a model of Input Iterator and InputIterator's value_type is convertible to OutputIterator's value_type.
OutputIteratoris 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.
Precondition
first may equal result but the range [first, last) and the range [result, result + (last - first)) shall not overlap otherwise.

The following code snippet demonstrates how to use exclusive_scan

#include <thrust/scan.h>
int data[6] = {1, 0, 2, 2, 1, 3};
thrust::exclusive_scan(data, data + 6, data); // in-place scan
// data is now {0, 1, 1, 3, 5, 6}
See also
https://en.cppreference.com/w/cpp/algorithm/partial_sum