Template Function thrust::reduce(InputIterator, InputIterator, T)¶
Function Documentation¶
-
template<typename
InputIterator
, typenameT
>
Tthrust
::
reduce
(InputIterator first, InputIterator last, T init) reduce
is a generalization of summation: it computes the sum (or some other binary operation) of all the elements in the range[first, last)
. This version ofreduce
usesinit
as the initial value of the reduction.reduce
is similar to the C++ Standard Template Library’sstd::accumulate
. The primary difference between the two functions is thatstd::accumulate
guarantees the order of summation, whilereduce
requires associativity of the binary operation to parallelize the reduction.Note that
reduce
also assumes that the binary reduction operator (in this case operator+) is commutative. If the reduction operator is not commutative thenthrust::reduce
should not be used. Instead, one could useinclusive_scan
(which does not require commutativity) and select the last element of the output array.The following code snippet demonstrates how to use
reduce
to compute the sum of a sequence of integers including an intialization value.- Return
The result of the reduction.
- Parameters
first
: The beginning of the input sequence.last
: The end of the input sequence.init
: The initial value.
- Template Parameters
InputIterator
: is a model of Input Iterator and ifx
andy
are objects ofInputIterator's
value_type
, thenx + y
is defined and is convertible toT
.T
: is convertible toInputIterator's
value_type
.
#include <thrust/reduce.h> ... int data[6] = {1, 0, 2, 2, 1, 3}; int result = thrust::reduce(data, data + 6, 1); // result == 10