abs acos acosh addressof adjacent_difference adjacent_difference adjacent_difference adjacent_difference advance all_of all_of any_of any_of arg asin asinh atan atanh bidirectional_host_iterator_tag binary_search binary_search binary_search binary_search binary_search binary_search binary_search binary_search conj conjunction conjunction_v conjunction_value_v copy copy copy_if copy_if copy_if copy_if copy_n copy_n cos cosh count count count_if count_if device device_delete device_free device_malloc device_new device_new device_new device_pointer_cast device_pointer_cast disjunction disjunction_v disjunction_value_v distance equal equal equal equal equal_range equal_range equal_range equal_range exclusive_scan exclusive_scan exclusive_scan exclusive_scan exclusive_scan exclusive_scan exclusive_scan_by_key exclusive_scan_by_key exclusive_scan_by_key exclusive_scan_by_key exclusive_scan_by_key exclusive_scan_by_key exclusive_scan_by_key exclusive_scan_by_key exp fill fill fill_n fill_n find find find_if find_if find_if_not find_if_not for_each for_each for_each_n for_each_n forward_host_iterator_tag free gather gather gather_if gather_if gather_if gather_if generate generate generate_n generate_n get get get_per_device_resource get_temporary_buffer host in_place inclusive_scan inclusive_scan inclusive_scan inclusive_scan inclusive_scan_by_key inclusive_scan_by_key inclusive_scan_by_key inclusive_scan_by_key inclusive_scan_by_key inclusive_scan_by_key index_sequence inner_product inner_product inner_product inner_product input_host_iterator_tag integer_sequence integer_sequence_push_back integer_sequence_push_front is_contiguous_iterator is_contiguous_iterator_v is_execution_policy is_execution_policy_v is_operator_greater_function_object is_operator_greater_function_object_v is_operator_less_function_object is_operator_less_function_object_v is_operator_less_or_greater_function_object is_operator_less_or_greater_function_object_v is_operator_plus_function_object is_operator_plus_function_object_v is_partitioned is_partitioned is_sorted is_sorted is_sorted is_sorted is_sorted_until is_sorted_until is_sorted_until is_sorted_until log log10 lower_bound lower_bound lower_bound lower_bound lower_bound lower_bound lower_bound lower_bound make_constant_iterator make_constant_iterator make_counting_iterator make_discard_iterator make_index_sequence make_integer_sequence make_pair make_permutation_iterator make_reverse_iterator make_reversed_index_sequence make_reversed_integer_sequence make_transform_input_output_iterator make_transform_iterator make_transform_output_iterator make_tuple make_tuple make_zip_function make_zip_iterator make_zip_iterator malloc malloc max_element max_element max_element max_element merge merge merge merge merge_by_key merge_by_key merge_by_key merge_by_key min_element min_element min_element min_element minmax_element minmax_element minmax_element minmax_element mismatch mismatch mismatch mismatch negation negation_v negation_value_v none_of none_of norm not1 not2 nullopt operator!= operator!= operator!= operator!= operator!= operator!= operator!= operator!= operator!= operator!= operator!= operator* operator* operator* operator+ operator+ operator+ operator+ operator- operator- operator- operator- operator/ operator/ operator/ operator< operator< operator< operator< operator< operator< operator<< operator<< operator<< operator<= operator<= operator<= operator<= operator<= operator<= operator== operator== operator== operator== operator== operator== operator== operator== operator== operator== operator== operator> operator> operator> operator> operator> operator> operator>= operator>= operator>= operator>= operator>= operator>= operator>> output_host_iterator_tag partition partition partition partition partition_copy partition_copy partition_copy partition_copy partition_point partition_point polar pow pow pow proj random_access_host_iterator_tag raw_pointer_cast raw_reference_cast raw_reference_cast reduce reduce reduce reduce reduce reduce reduce_by_key reduce_by_key reduce_by_key reduce_by_key reduce_by_key reduce_by_key remove remove remove_copy remove_copy remove_copy_if remove_copy_if remove_copy_if remove_copy_if remove_cvref_t remove_if remove_if remove_if remove_if replace replace replace_copy replace_copy replace_copy_if replace_copy_if replace_copy_if replace_copy_if replace_if replace_if replace_if replace_if return_temporary_buffer reverse reverse reverse_copy reverse_copy scatter scatter scatter_if scatter_if scatter_if scatter_if sequence sequence sequence sequence sequence sequence set_difference set_difference set_difference set_difference set_difference_by_key set_difference_by_key set_difference_by_key set_difference_by_key set_intersection set_intersection set_intersection set_intersection set_intersection_by_key set_intersection_by_key set_intersection_by_key set_intersection_by_key set_symmetric_difference set_symmetric_difference set_symmetric_difference set_symmetric_difference set_symmetric_difference_by_key set_symmetric_difference_by_key set_symmetric_difference_by_key set_symmetric_difference_by_key set_union set_union set_union set_union set_union_by_key set_union_by_key set_union_by_key set_union_by_key shuffle shuffle shuffle_copy shuffle_copy sin sinh sort sort sort sort sort_by_key sort_by_key sort_by_key sort_by_key sqrt stable_partition stable_partition stable_partition stable_partition stable_partition_copy stable_partition_copy stable_partition_copy stable_partition_copy stable_sort stable_sort stable_sort stable_sort stable_sort_by_key stable_sort_by_key stable_sort_by_key stable_sort_by_key swap swap swap swap swap swap swap swap_ranges swap_ranges tabulate tabulate tan tanh THRUST_PREVENT_MACRO_SUBSTITUTION THRUST_PREVENT_MACRO_SUBSTITUTION THRUST_PREVENT_MACRO_SUBSTITUTION THRUST_PREVENT_MACRO_SUBSTITUTION tie tie transform transform transform transform transform_exclusive_scan transform_exclusive_scan transform_if transform_if transform_if transform_if transform_if transform_if transform_inclusive_scan transform_inclusive_scan transform_reduce transform_reduce uninitialized_copy uninitialized_copy uninitialized_copy_n uninitialized_copy_n uninitialized_fill uninitialized_fill uninitialized_fill_n uninitialized_fill_n unique unique unique unique unique_by_key unique_by_key unique_by_key unique_by_key unique_by_key_copy unique_by_key_copy unique_by_key_copy unique_by_key_copy unique_copy unique_copy unique_copy unique_copy unique_count unique_count unique_count unique_count universal_ptr upper_bound upper_bound upper_bound upper_bound upper_bound upper_bound upper_bound upper_bound

reduce_by_key() [1/6] template<typename DerivedPolicy , typename InputIterator1 , typename InputIterator2 , typename OutputIterator1 , typename OutputIterator2 > __host__ __device__ thrust::pair<OutputIterator1,OutputIterator2> thrust::reduce_by_key ( const thrust::detail::execution_policy_base< DerivedPolicy > &  exec, 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. The algorithm's execution is parallelized as determined by exec. Parameters exec The execution policy to use for parallelization. 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 DerivedPolicy The name of the derived execution policy. 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. Precondition The input ranges shall not overlap either output range. 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 using the thrust::host execution policy for parallelization: #include <thrust/reduce.h> #include <thrust/execution_policy.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(thrust::host, 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