thrust::count

Defined in thrust/count.h

template<typename DerivedPolicy, typename InputIterator, typename EqualityComparable> thrust::detail::it_difference_t<InputIterator> thrust::count(const thrust::detail::execution_policy_base<DerivedPolicy> &exec, InputIterator first, InputIterator last, const EqualityComparable &value)

count finds the number of elements in [first,last) that are equal to value. More precisely, count returns the number of iterators i in [first, last) such that *i == value.

The algorithm’s execution is parallelized as determined by exec.

The following code snippet demonstrates how to use count to count the number of instances in a range of a value of interest using the thrust::device execution policy:

#include <thrust/count.h>
#include <thrust/device_vector.h>
#include <thrust/execution_policy.h>
...
// put 3 1s in a device_vector
thrust::device_vector<int> vec(5,0);
vec[1] = 1;
vec[3] = 1;
vec[4] = 1;

// count the 1s
int result = thrust::count(thrust::device, vec.begin(), vec.end(), 1);
// result == 3