thrust::equal_range

Defined in thrust/binary_search.h

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

equal_range is a version of binary search: it attempts to find the element value in an ordered range [first, last). The value returned by equal_range is essentially a combination of the values returned by lower_bound and upper_bound: it returns a pair of iterators i and j such that i is the first position where value could be inserted without violating the ordering and j is the last position where value could be inserted without violating the ordering. It follows that every element in the range [i, j) is equivalent to value, and that [i, j) is the largest subrange of [first, last) that has this property.

This version of equal_range returns a pair of iterators [i, j), where i is the furthermost iterator in [first, last) such that, for every iterator k in [first, i), *k < value. j is the furthermost iterator in [first, last) such that, for every iterator k in [first, j), value < *k is false. For every iterator k in [i, j), neither value < *k nor *k < value is true.

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

The following code snippet demonstrates how to use equal_range 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::equal_range(thrust::device, input.begin(), input.end(), 0); // returns [input.begin(), input.begin() + 1)
 thrust::equal_range(thrust::device, input.begin(), input.end(), 1); // returns [input.begin() + 1, input.begin() +
1) thrust::equal_range(thrust::device, input.begin(), input.end(), 2); // returns [input.begin() + 1, input.begin() +
2) thrust::equal_range(thrust::device, input.begin(), input.end(), 3); // returns [input.begin() + 2, input.begin() +
2) thrust::equal_range(thrust::device, input.begin(), input.end(), 8); // returns [input.begin() + 4, input.end)
 thrust::equal_range(thrust::device, input.begin(), input.end(), 9); // returns [input.end(), input.end)

See also

lower_bound

See also

upper_bound

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

A pair of iterators [i, j) that define the range of equivalent elements.