thrust::lower_bound

Defined in thrust/binary_search.h

template<typename DerivedPolicy, typename ForwardIterator, typename LessThanComparable> ForwardIterator thrust::lower_bound(const thrust::detail::execution_policy_base<DerivedPolicy> &exec, ForwardIterator first, ForwardIterator last, const LessThanComparable &value)

lower_bound is a version of binary search: it attempts to find the element value in an ordered range [first, last). Specifically, it returns the first position where value could be inserted without violating the ordering. This version of lower_bound uses operator< for comparison and returns the furthermost iterator i in [first, last) such that, for every iterator j in [first, i), *j < value.

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

The following code snippet demonstrates how to use lower_bound to search for values in a ordered range using the thrust::device execution policy for parallelization:

#include <thrust/binary_search.h>
#include <thrust/device_vector.h>
#include <thrust/execution_policy.h>
...
thrust::device_vector<int> input(5);

input[0] = 0;
input[1] = 2;
input[2] = 5;
input[3] = 7;
input[4] = 8;

thrust::lower_bound(thrust::device, input.begin(), input.end(), 0); // returns input.begin()
thrust::lower_bound(thrust::device, input.begin(), input.end(), 1); // returns input.begin() + 1
thrust::lower_bound(thrust::device, input.begin(), input.end(), 2); // returns input.begin() + 1
thrust::lower_bound(thrust::device, input.begin(), input.end(), 3); // returns input.begin() + 2
thrust::lower_bound(thrust::device, input.begin(), input.end(), 8); // returns input.begin() + 4
thrust::lower_bound(thrust::device, input.begin(), input.end(), 9); // returns input.end()

See also

upper_bound

See also

equal_range

See also

Binary Search

Parameters

exec – The execution policy to use for parallelization.
first – The beginning of the ordered sequence.
last – The end of the ordered sequence.
value – The value to be searched.

Template Parameters

DerivedPolicy – The name of the derived execution policy.
ForwardIterator – is a model of Forward Iterator.
LessThanComparable – is a model of LessThanComparable.

Returns

The furthermost iterator i, such that *i < value.