thrust::lower_bound

Defined in thrust/binary_search.h

template<class ForwardIterator, class T, class StrictWeakOrdering> ForwardIterator thrust::lower_bound(ForwardIterator first, ForwardIterator last, const T &value, StrictWeakOrdering comp)

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 function object comp for comparison and returns the furthermost iterator i in [first, last) such that, for every iterator j in [first, i), comp(*j, value) is true.

The following code snippet demonstrates how to use lower_bound to search for values in a ordered range.

#include <thrust/binary_search.h>
#include <thrust/device_vector.h>
#include <thrust/functional.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(input.begin(), input.end(), 0, thrust::less<int>()); // returns input.begin()
thrust::lower_bound(input.begin(), input.end(), 1, thrust::less<int>()); // returns input.begin() + 1
thrust::lower_bound(input.begin(), input.end(), 2, thrust::less<int>()); // returns input.begin() + 1
thrust::lower_bound(input.begin(), input.end(), 3, thrust::less<int>()); // returns input.begin() + 2
thrust::lower_bound(input.begin(), input.end(), 8, thrust::less<int>()); // returns input.begin() + 4
thrust::lower_bound(input.begin(), input.end(), 9, thrust::less<int>()); // returns input.end()

See also

upper_bound

See also

equal_range

See also

Binary Search

Parameters

first – The beginning of the ordered sequence.
last – The end of the ordered sequence.
value – The value to be searched.
comp – The comparison operator.

Template Parameters

ForwardIterator – is a model of Forward Iterator.
T – is comparable to ForwardIterator's value_type.
StrictWeakOrdering – is a model of Strict Weak Ordering.

Returns

The furthermost iterator i, such that comp(*i, value) is true.