Binary Search

Modules
	Vectorized Searches
Functions
template<class ForwardIterator , class LessThanComparable >
ForwardIterator	thrust::lower_bound (ForwardIterator first, ForwardIterator last, const LessThanComparable &value)
template<class ForwardIterator , class T , class StrictWeakOrdering >
ForwardIterator	thrust::lower_bound (ForwardIterator first, ForwardIterator last, const T &value, StrictWeakOrdering comp)
template<class ForwardIterator , class LessThanComparable >
ForwardIterator	thrust::upper_bound (ForwardIterator first, ForwardIterator last, const LessThanComparable &value)
template<class ForwardIterator , class T , class StrictWeakOrdering >
ForwardIterator	thrust::upper_bound (ForwardIterator first, ForwardIterator last, const T &value, StrictWeakOrdering comp)
template<class ForwardIterator , class LessThanComparable >
bool	thrust::binary_search (ForwardIterator first, ForwardIterator last, const LessThanComparable &value)
template<class ForwardIterator , class T , class StrictWeakOrdering >
bool	thrust::binary_search (ForwardIterator first, ForwardIterator last, const T &value, StrictWeakOrdering comp)
template<class ForwardIterator , class LessThanComparable >
thrust::pair< ForwardIterator, ForwardIterator >	thrust::equal_range (ForwardIterator first, ForwardIterator last, const LessThanComparable &value)
template<class ForwardIterator , class T , class StrictWeakOrdering >
thrust::pair< ForwardIterator, ForwardIterator >	thrust::equal_range (ForwardIterator first, ForwardIterator last, const T &value, StrictWeakOrdering comp)

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Function Documentation

template<class ForwardIterator , class LessThanComparable >

bool thrust::binary_search	(	ForwardIterator	first,
		ForwardIterator	last,
		const LessThanComparable &	value
	)

binary_search is a version of binary search: it attempts to find the element value in an ordered range [first, last). It returns true if an element that is equivalent to value is present in [first, last) and false if no such element exists. Specifically, this version returns true if and only if there exists an iterator i in [first, last) such that *i < value and value < *i are both false.

Parameters:

first	The beginning of the ordered sequence.
last	The end of the ordered sequence.
value	The value to be searched.

Returns:

true if an equivalent element exists in [first, last), otherwise false.

Template Parameters:

ForwardIterator	is a model of Forward Iterator.
LessThanComparable	is a model of LessThanComparable.

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

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

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

  thrust::binary_search(input.begin(), input.end(), 0); // returns true
  thrust::binary_search(input.begin(), input.end(), 1); // returns false
  thrust::binary_search(input.begin(), input.end(), 2); // returns true
  thrust::binary_search(input.begin(), input.end(), 3); // returns false
  thrust::binary_search(input.begin(), input.end(), 8); // returns true
  thrust::binary_search(input.begin(), input.end(), 9); // returns false

See also:

http://www.sgi.com/tech/stl/binary_search.html

lower_bound

upper_bound

equal_range

template<class ForwardIterator , class T , class StrictWeakOrdering >

bool thrust::binary_search	(	ForwardIterator	first,
		ForwardIterator	last,
		const T &	value,
		StrictWeakOrdering	comp
	)

binary_search is a version of binary search: it attempts to find the element value in an ordered range [first, last). It returns true if an element that is equivalent to value is present in [first, last) and false if no such element exists. Specifically, this version returns true if and only if there exists an iterator i in [first, last) such that comp(*i, value) and comp(value, *i) are both false.

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.

Returns:

true if an equivalent element exists in [first, last), otherwise false.

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.

The following code snippet demonstrates how to use binary_search 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::binary_search(input.begin(), input.end(), 0, thrust::less<int>()); // returns true
  thrust::binary_search(input.begin(), input.end(), 1, thrust::less<int>()); // returns false
  thrust::binary_search(input.begin(), input.end(), 2, thrust::less<int>()); // returns true
  thrust::binary_search(input.begin(), input.end(), 3, thrust::less<int>()); // returns false
  thrust::binary_search(input.begin(), input.end(), 8, thrust::less<int>()); // returns true
  thrust::binary_search(input.begin(), input.end(), 9, thrust::less<int>()); // returns false

See also:

http://www.sgi.com/tech/stl/binary_search.html

lower_bound

upper_bound

equal_range

template<class ForwardIterator , class T , class StrictWeakOrdering >

thrust::pair<ForwardIterator, ForwardIterator> thrust::equal_range	(	ForwardIterator	first,
		ForwardIterator	last,
		const T &	value,
		StrictWeakOrdering	comp
	)

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). i is the furthermost iterator in [first, last) such that, for every iterator k in [first, i), comp(*k, value) is true. j is the furthermost iterator in [first, last) such that, for every iterator k in [first, last), comp(value, *k) is false. For every iterator k in [i, j), neither comp(value, *k) nor comp(*k, value) is true.

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.

Returns:

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

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.

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

See also:

http://www.sgi.com/tech/stl/equal_range.html

lower_bound

upper_bound

binary_search

template<class ForwardIterator , class LessThanComparable >

thrust::pair<ForwardIterator, ForwardIterator> thrust::equal_range	(	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.

Parameters:

first	The beginning of the ordered sequence.
last	The end of the ordered sequence.
value	The value to be searched.

Returns:

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

Template Parameters:

ForwardIterator	is a model of Forward Iterator.
LessThanComparable	is a model of LessThanComparable.

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

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

See also:

http://www.sgi.com/tech/stl/equal_range.html

lower_bound

upper_bound

binary_search

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.

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.

Returns:

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

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.

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:

http://www.sgi.com/tech/stl/lower_bound.html

upper_bound

equal_range

binary_search

template<class ForwardIterator , class LessThanComparable >

ForwardIterator thrust::lower_bound	(	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.

Parameters:

first	The beginning of the ordered sequence.
last	The end of the ordered sequence.
value	The value to be searched.

Returns:

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

Template Parameters:

ForwardIterator	is a model of Forward Iterator.
LessThanComparable	is a model of LessThanComparable.

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

See also:

http://www.sgi.com/tech/stl/lower_bound.html

upper_bound

equal_range

binary_search

template<class ForwardIterator , class LessThanComparable >

ForwardIterator thrust::upper_bound	(	ForwardIterator	first,
		ForwardIterator	last,
		const LessThanComparable &	value
	)

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

Parameters:

first	The beginning of the ordered sequence.
last	The end of the ordered sequence.
value	The value to be searched.

Returns:

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

Template Parameters:

ForwardIterator	is a model of Forward Iterator.
LessThanComparable	is a model of LessThanComparable.

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

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

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

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

See also:

http://www.sgi.com/tech/stl/upper_bound.html

lower_bound

equal_range

binary_search

template<class ForwardIterator , class T , class StrictWeakOrdering >

ForwardIterator thrust::upper_bound	(	ForwardIterator	first,
		ForwardIterator	last,
		const T &	value,
		StrictWeakOrdering	comp
	)

upper_bound is a version of binary search: it attempts to find the element value in an ordered range [first, last). Specifically, it returns the last position where value could be inserted without violating the ordering. This version of upper_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(value, *j) is false.

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.

Returns:

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

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.

The following code snippet demonstrates how to use upper_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::upper_bound(input.begin(), input.end(), 0, thrust::less<int>()); // returns input.begin() + 1
  thrust::upper_bound(input.begin(), input.end(), 1, thrust::less<int>()); // returns input.begin() + 1
  thrust::upper_bound(input.begin(), input.end(), 2, thrust::less<int>()); // returns input.begin() + 2
  thrust::upper_bound(input.begin(), input.end(), 3, thrust::less<int>()); // returns input.begin() + 2
  thrust::upper_bound(input.begin(), input.end(), 8, thrust::less<int>()); // returns input.end()
  thrust::upper_bound(input.begin(), input.end(), 9, thrust::less<int>()); // returns input.end()

See also:

http://www.sgi.com/tech/stl/upper_bound.html

lower_bound

equal_range

binary_search