thrust::inner_product

Defined in thrust/inner_product.h

template<typename InputIterator1, typename InputIterator2, typename OutputType>
OutputType thrust::inner_product(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, OutputType init)

inner_product calculates an inner product of the ranges [first1, last1) and [first2, first2 + (last1 - first1)).

Specifically, this version of inner_product computes the sum init + (*first1 * *first2) + (*(first1+1) * *(first2+1)) + ...

Unlike the C++ Standard Template Library function std::inner_product, this version offers no guarantee on order of execution.

The following code demonstrates how to use inner_product to compute the dot product of two vectors.

#include <thrust/inner_product.h>
...
float vec1[3] = {1.0f, 2.0f, 5.0f};
float vec2[3] = {4.0f, 1.0f, 5.0f};

float result = thrust::inner_product(vec1, vec1 + 3, vec2, 0.0f);

// result == 31.0f

See also

https://en.cppreference.com/w/cpp/algorithm/inner_product

Parameters

• first1 – The beginning of the first sequence.

• last1 – The end of the first sequence.

• first2 – The beginning of the second sequence.

• init – Initial value of the result.

Template Parameters

• InputIterator1 – is a model of Input Iterator,

• InputIterator2 – is a model of Input Iterator,

• OutputType – is a model of Assignable, and if x is an object of type OutputType, and y is an object of InputIterator1's value_type, and z is an object of InputIterator2's value_type, then x + y * z is defined and is convertible to OutputType.

Returns

The inner product of sequences [first1, last1) and [first2, last2) plus init.