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template<typename InputIterator >
thrust::iterator_traits < InputIterator >::value_type	thrust::reduce (InputIterator first, InputIterator last)
template<typename InputIterator , typename T >
T	thrust::reduce (InputIterator first, InputIterator last, T init)
template<typename InputIterator , typename T , typename BinaryFunction >
T	thrust::reduce (InputIterator first, InputIterator last, T init, BinaryFunction binary_op)
template<typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 >
thrust::pair< OutputIterator1, OutputIterator2 >	thrust::reduce_by_key (InputIterator1 keys_first, InputIterator1 keys_last, InputIterator2 values_first, OutputIterator1 keys_output, OutputIterator2 values_output)
template<typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 , typename BinaryPredicate >
thrust::pair< OutputIterator1, OutputIterator2 >	thrust::reduce_by_key (InputIterator1 keys_first, InputIterator1 keys_last, InputIterator2 values_first, OutputIterator1 keys_output, OutputIterator2 values_output, BinaryPredicate binary_pred)
template<typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 , typename BinaryPredicate , typename BinaryFunction >
thrust::pair< OutputIterator1, OutputIterator2 >	thrust::reduce_by_key (InputIterator1 keys_first, InputIterator1 keys_last, InputIterator2 values_first, OutputIterator1 keys_output, OutputIterator2 values_output, BinaryPredicate binary_pred, BinaryFunction binary_op)

Detailed Description

// searching

// end sorting

Function Documentation

template<typename InputIterator >

thrust::iterator_traits<InputIterator>::value_type thrust::reduce	(	InputIterator	first,
		InputIterator	last
	)

reduce is a generalization of summation: it computes the sum (or some other binary operation) of all the elements in the range [first, last). This version of reduce uses 0 as the initial value of the reduction. reduce is similar to the C++ Standard Template Library's std::accumulate. The primary difference between the two functions is that std::accumulate guarantees the order of summation, while reduce requires associativity of the binary operation to parallelize the reduction.

Note that reduce also assumes that the binary reduction operator (in this case operator+) is commutative. If the reduction operator is not commutative then thrust::reduce should not be used. Instead, one could use inclusive_scan (which does not require commutativity) and select the last element of the output array.

Parameters:

first	The beginning of the sequence.
last	The end of the sequence.

Returns:: The result of the reduction.

Template Parameters:

InputIterator is a model of Input Iterator and if x and y are objects of InputIterator's value_type, then x + y is defined and is convertible to InputIterator's value_type. If T is InputIterator's value_type, then T(0) is defined.

The following code snippet demonstrates how to use reduce to compute the sum of a sequence of integers.

  #include <thrust/reduce.h>
  ...
  int data[6] = {1, 0, 2, 2, 1, 3};
  int result = thrust::reduce(data, data + 6);

  // result == 9

See also:: http://www.sgi.com/tech/stl/accumulate.html

template<typename InputIterator , typename T >

T thrust::reduce	(	InputIterator	first,
		InputIterator	last,
		T	init
	)

reduce is a generalization of summation: it computes the sum (or some other binary operation) of all the elements in the range [first, last). This version of reduce uses init as the initial value of the reduction. reduce is similar to the C++ Standard Template Library's std::accumulate. The primary difference between the two functions is that std::accumulate guarantees the order of summation, while reduce requires associativity of the binary operation to parallelize the reduction.

Note that reduce also assumes that the binary reduction operator (in this case operator+) is commutative. If the reduction operator is not commutative then thrust::reduce should not be used. Instead, one could use inclusive_scan (which does not require commutativity) and select the last element of the output array.

Parameters:

first	The beginning of the input sequence.
last	The end of the input sequence.
init	The initial value.

Returns:: The result of the reduction.

Template Parameters:

InputIterator	is a model of Input Iterator and if `x` and `y` are objects of `InputIterator's` `value_type`, then `x + y` is defined and is convertible to `T`.
T	is convertible to `InputIterator's` `value_type`.

The following code snippet demonstrates how to use reduce to compute the sum of a sequence of integers including an intialization value.

  #include <thrust/reduce.h>
  ...
  int data[6] = {1, 0, 2, 2, 1, 3};
  int result = thrust::reduce(data, data + 6, 1);

  // result == 10

See also:: http://www.sgi.com/tech/stl/accumulate.html

template<typename InputIterator , typename T , typename BinaryFunction >

T thrust::reduce	(	InputIterator	first,
		InputIterator	last,
		T	init,
		BinaryFunction	binary_op
	)

reduce is a generalization of summation: it computes the sum (or some other binary operation) of all the elements in the range [first, last). This version of reduce uses init as the initial value of the reduction and binary_op as the binary function used for summation. reduce is similar to the C++ Standard Template Library's std::accumulate. The primary difference between the two functions is that std::accumulate guarantees the order of summation, while reduce requires associativity of binary_op to parallelize the reduction.

Note that reduce also assumes that the binary reduction operator (in this case binary_op) is commutative. If the reduction operator is not commutative then thrust::reduce should not be used. Instead, one could use inclusive_scan (which does not require commutativity) and select the last element of the output array.

Parameters:

first	The beginning of the input sequence.
last	The end of the input sequence.
init	The initial value.
binary_op	The binary function used to 'sum' values.

Returns:: The result of the reduction.

Template Parameters:

InputIterator	is a model of Input Iterator and `InputIterator's` `value_type` is convertible to `T`.
T	is a model of Assignable, and is convertible to `BinaryFunction's` `first_argument_type` and `second_argument_type`.
BinaryFunction	is a model of Binary Function, and `BinaryFunction's` `result_type` is convertible to `OutputType`.

The following code snippet demonstrates how to use reduce to compute the maximum value of a sequence of integers.

  #include <thrust/reduce.h>
  #include <thrust/functional.h>
  ...
  int data[6] = {1, 0, 2, 2, 1, 3};
  int result = thrust::reduce(data, data + 6,
                              -1,
                              thrust::maximum<int>());
  // result == 3

See also:: http://www.sgi.com/tech/stl/accumulate.html; transform_reduce

template<typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 >

thrust::pair<OutputIterator1,OutputIterator2> thrust::reduce_by_key	(	InputIterator1	keys_first,
		InputIterator1	keys_last,
		InputIterator2	values_first,
		OutputIterator1	keys_output,
		OutputIterator2	values_output
	)

reduce_by_key is a generalization of reduce to key-value pairs. For each group of consecutive keys in the range [keys_first, keys_last) that are equal, reduce_by_key copies the first element of the group to the keys_output. The corresponding values in the range are reduced using the plus and the result copied to values_output.

This version of reduce_by_key uses the function object equal_to to test for equality and plus to reduce values with equal keys.

Parameters:

keys_first	The beginning of the input key range.
keys_last	The end of the input key range.
values_first	The beginning of the input value range.
keys_output	The beginning of the output key range.
values_output	The beginning of the output value range.

Returns:: A pair of iterators at end of the ranges [keys_output, keys_output_last) and [values_output, values_output_last).

Template Parameters:

InputIterator1	is a model of Input Iterator,
InputIterator2	is a model of Input Iterator,
OutputIterator1	is a model of Output Iterator and and `InputIterator1's` `value_type` is convertible to `OutputIterator1's` `value_type`.
OutputIterator2	is a model of Output Iterator and and `InputIterator2's` `value_type` is convertible to `OutputIterator2's` `value_type`.

The following code snippet demonstrates how to use reduce_by_key to compact a sequence of key/value pairs and sum values with equal keys.

  #include <thrust/reduce.h>
  ...
  const int N = 7;
  int A[N] = {1, 3, 3, 3, 2, 2, 1}; // input keys
  int B[N] = {9, 8, 7, 6, 5, 4, 3}; // input values
  int C[N];                         // output keys
  int D[N];                         // output values

  thrust::pair<int*,int*> new_end;
  new_end = thrust::reduce_by_key(A, A + N, B, C, D);

  // The first four keys in C are now {1, 3, 2, 1} and new_end.first - C is 4.
  // The first four values in D are now {9, 21, 9, 3} and new_end.second - D is 4.

See also:: reduce; unique_copy; unique_by_key; unique_by_key_copy

template<typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 , typename BinaryPredicate >

thrust::pair<OutputIterator1,OutputIterator2> thrust::reduce_by_key	(	InputIterator1	keys_first,
		InputIterator1	keys_last,
		InputIterator2	values_first,
		OutputIterator1	keys_output,
		OutputIterator2	values_output,
		BinaryPredicate	binary_pred
	)

reduce_by_key is a generalization of reduce to key-value pairs. For each group of consecutive keys in the range [keys_first, keys_last) that are equal, reduce_by_key copies the first element of the group to the keys_output. The corresponding values in the range are reduced using the plus and the result copied to values_output.

This version of reduce_by_key uses the function object binary_pred to test for equality and plus to reduce values with equal keys.

Parameters:

keys_first	The beginning of the input key range.
keys_last	The end of the input key range.
values_first	The beginning of the input value range.
keys_output	The beginning of the output key range.
values_output	The beginning of the output value range.
binary_pred	The binary predicate used to determine equality.

Returns:: A pair of iterators at end of the ranges [keys_output, keys_output_last) and [values_output, values_output_last).

Template Parameters:

InputIterator1	is a model of Input Iterator,
InputIterator2	is a model of Input Iterator,
OutputIterator1	is a model of Output Iterator and and `InputIterator1's` `value_type` is convertible to `OutputIterator1's` `value_type`.
OutputIterator2	is a model of Output Iterator and and `InputIterator2's` `value_type` is convertible to `OutputIterator2's` `value_type`.
BinaryPredicate	is a model of Binary Predicate.

The following code snippet demonstrates how to use reduce_by_key to compact a sequence of key/value pairs and sum values with equal keys.

  #include <thrust/reduce.h>
  ...
  const int N = 7;
  int A[N] = {1, 3, 3, 3, 2, 2, 1}; // input keys
  int B[N] = {9, 8, 7, 6, 5, 4, 3}; // input values
  int C[N];                         // output keys
  int D[N];                         // output values

  thrust::pair<int*,int*> new_end;
  thrust::equal_to<int> binary_pred;
  new_end = thrust::reduce_by_key(A, A + N, B, C, D, binary_pred);

  // The first four keys in C are now {1, 3, 2, 1} and new_end.first - C is 4.
  // The first four values in D are now {9, 21, 9, 3} and new_end.second - D is 4.

See also:: reduce; unique_copy; unique_by_key; unique_by_key_copy

template<typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 , typename BinaryPredicate , typename BinaryFunction >

thrust::pair<OutputIterator1,OutputIterator2> thrust::reduce_by_key	(	InputIterator1	keys_first,
		InputIterator1	keys_last,
		InputIterator2	values_first,
		OutputIterator1	keys_output,
		OutputIterator2	values_output,
		BinaryPredicate	binary_pred,
		BinaryFunction	binary_op
	)

reduce_by_key is a generalization of reduce to key-value pairs. For each group of consecutive keys in the range [keys_first, keys_last) that are equal, reduce_by_key copies the first element of the group to the keys_output. The corresponding values in the range are reduced using the BinaryFunction binary_op and the result copied to values_output. Specifically, if consecutive key iterators i and (i + 1) are such that binary_pred(*i, *(i+1)) is true, then the corresponding values are reduced to a single value with binary_op.

This version of reduce_by_key uses the function object binary_pred to test for equality and binary_op to reduce values with equal keys.

Parameters:

keys_first	The beginning of the input key range.
keys_last	The end of the input key range.
values_first	The beginning of the input value range.
keys_output	The beginning of the output key range.
values_output	The beginning of the output value range.
binary_pred	The binary predicate used to determine equality.
binary_op	The binary function used to accumulate values.

Returns:: A pair of iterators at end of the ranges [keys_output, keys_output_last) and [values_output, values_output_last).

Template Parameters:

InputIterator1	is a model of Input Iterator,
InputIterator2	is a model of Input Iterator,
OutputIterator1	is a model of Output Iterator and and `InputIterator1's` `value_type` is convertible to `OutputIterator1's` `value_type`.
OutputIterator2	is a model of Output Iterator and and `InputIterator2's` `value_type` is convertible to `OutputIterator2's` `value_type`.
BinaryPredicate	is a model of Binary Predicate.
BinaryFunction	is a model of Binary Function and `BinaryFunction's` `result_type` is convertible to `OutputIterator2's` `value_type`.

The following code snippet demonstrates how to use reduce_by_key to compact a sequence of key/value pairs and sum values with equal keys.

  #include <thrust/reduce.h>
  ...
  const int N = 7;
  int A[N] = {1, 3, 3, 3, 2, 2, 1}; // input keys
  int B[N] = {9, 8, 7, 6, 5, 4, 3}; // input values
  int C[N];                         // output keys
  int D[N];                         // output values

  thrust::pair<int*,int*> new_end;
  thrust::equal_to<int> binary_pred;
  thrust::plus<int> binary_op;
  new_end = thrust::reduce_by_key(A, A + N, B, C, D, binary_pred, binary_op);

  // The first four keys in C are now {1, 3, 2, 1} and new_end.first - C is 4.
  // The first four values in D are now {9, 21, 9, 3} and new_end.second - D is 4.

See also:: reduce; unique_copy; unique_by_key; unique_by_key_copy

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