Template Function thrust::unique_by_key(ForwardIterator1, ForwardIterator1, ForwardIterator2, BinaryPredicate)

Function Documentation

template<typename ForwardIterator1, typename ForwardIterator2, typename BinaryPredicate>
thrust::pair<ForwardIterator1, ForwardIterator2> thrust::unique_by_key(ForwardIterator1 keys_first, ForwardIterator1 keys_last, ForwardIterator2 values_first, BinaryPredicate binary_pred)

unique_by_key is a generalization of unique to key-value pairs. For each group of consecutive keys in the range [keys_first, keys_last) that are equal, unique_by_key removes all but the first element of the group. Similarly, the corresponding values in the range [values_first, values_first + (keys_last - keys_first)) are also removed.

This version of unique_by_key uses the function object binary_pred to test for equality and project1st to reduce values with equal keys.

The following code snippet demonstrates how to use

unique_by_key to compact a sequence of key/value pairs to remove consecutive duplicates.
Return

The end of the unique range [first, new_last).

Pre

The range [keys_first, keys_last) and the range [values_first, values_first + (keys_last - keys_first)) shall not overlap.

Parameters

  • keys_first: The beginning of the key range.

  • keys_last: The end of the key range.

  • values_first: The beginning of the value range.

  • binary_pred: The binary predicate used to determine equality.

Template Parameters

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

thrust::pair<int*,int*> new_end;
thrust::equal_to<int> binary_pred;
new_end = thrust::unique_by_key(keys, keys + N, values, binary_pred);

// The first four keys in A are now {1, 3, 2, 1} and new_end.first - A is 4.
// The first four values in B are now {9, 8, 5, 3} and new_end.second - B is 4.

See

unique

See

unique_by_key_copy

See

reduce_by_key