__GNU_PARALLEL::_SETTINGS(3)

💖 __gnu_parallel::_Settings(3) 💖

okay so this is the __gnu_parallel::_Settings(3) page from the Library Functions Manual, and it's literally the settings class for parallel mode. No cap, it's giving “tunable parameters” energy ✨

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🌸 NAME 🌸

__gnu_parallel::_Settings — class _Settings. Run-time settings for the parallel mode including all tunable parameters.

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✨ SYNOPSIS ✨

#include <settings.h>

💅 Static Public Member Functions

• static const _Settings & get () throw () — Get the global settings.
• static void set (_Settings &) throw () — Set the global settings.

🎀 Public Attributes

• _SequenceIndex accumulate_minimal_n — Minimal input size for accumulate.
• unsigned int adjacent_difference_minimal_n — Minimal input size for adjacent_difference.
• _AlgorithmStrategy algorithm_strategy
• unsigned int cache_line_size — Overestimation of cache line size. Used to avoid false sharing, i.e. elements of different threads are at least this amount apart.
• _SequenceIndex count_minimal_n — Minimal input size for count and count_if.
• _SequenceIndex fill_minimal_n — Minimal input size for fill.
• _FindAlgorithm find_algorithm
• double find_increasing_factor — Block size increase factor for find.
• _SequenceIndex find_initial_block_size — Initial block size for find.
• _SequenceIndex find_maximum_block_size — Maximal block size for find.
• float find_scale_factor — Block size scale-down factor with respect to current position.
• _SequenceIndex find_sequential_search_size — Start with looking for this many elements sequentially, for find.
• _SequenceIndex for_each_minimal_n — Minimal input size for for_each.
• _SequenceIndex generate_minimal_n — Minimal input size for generate.
• unsigned long long L1_cache_size — size of the L1 cache in bytes (underestimation).
• unsigned long long L2_cache_size — size of the L2 cache in bytes (underestimation).
• _SequenceIndex max_element_minimal_n — Minimal input size for max_element.
• _SequenceIndex merge_minimal_n — Minimal input size for merge.
• unsigned int merge_oversampling — Oversampling factor for merge.
• _SplittingAlgorithm merge_splitting
• _SequenceIndex min_element_minimal_n — Minimal input size for min_element.
• _MultiwayMergeAlgorithm multiway_merge_algorithm
• int multiway_merge_minimal_k — Oversampling factor for multiway_merge.
• _SequenceIndex multiway_merge_minimal_n — Minimal input size for multiway_merge.
• unsigned int multiway_merge_oversampling — Oversampling factor for multiway_merge.
• _SplittingAlgorithm multiway_merge_splitting
• _SequenceIndex nth_element_minimal_n — Minimal input size for nth_element.
• _SequenceIndex partial_sort_minimal_n — Minimal input size for partial_sort.
• _PartialSumAlgorithm partial_sum_algorithm
• float partial_sum_dilation — Ratio for partial_sum. Assume sumandwriteresult"tobethisfactorslowerthanjustsum.
• unsigned int partial_sum_minimal_n — Minimal input size for partial_sum.
• double partition_chunk_share — Chunk size for partition, relative to input size. If > 0.0, this value overrides partition_chunk_size.
• _SequenceIndex partition_chunk_size — Chunk size for partition.
• _SequenceIndex partition_minimal_n — Minimal input size for partition.
• _SequenceIndex qsb_steals — The number of stolen ranges in load-balanced quicksort.
• unsigned int random_shuffle_minimal_n — Minimal input size for random_shuffle.
• _SequenceIndex replace_minimal_n — Minimal input size for replace and replace_if.
• _SequenceIndex search_minimal_n — Minimal input size for search and search_n.
• _SequenceIndex set_difference_minimal_n — Minimal input size for set_difference.
• _SequenceIndex set_intersection_minimal_n — Minimal input size for set_intersection.
• _SequenceIndex set_symmetric_difference_minimal_n — Minimal input size for set_symmetric_difference.
• _SequenceIndex set_union_minimal_n — Minimal input size for set_union.
• _SortAlgorithm sort_algorithm
• _SequenceIndex sort_minimal_n — Minimal input size for parallel sorting.
• unsigned int sort_mwms_oversampling — Oversampling factor for parallel std::sort (MWMS).
• unsigned int sort_qs_num_samples_preset — Such many samples to take to find a good pivot (quicksort).
• _SequenceIndex sort_qsb_base_case_maximal_n — Maximal subsequence __length to switch to unbalanced __base case. Applies to std::sort with dynamically load-balanced quicksort.
• _SplittingAlgorithm sort_splitting
• unsigned int TLB_size — size of the Translation Lookaside Buffer (underestimation).
• _SequenceIndex transform_minimal_n — Minimal input size for parallel std::transform.
• _SequenceIndex unique_copy_minimal_n — Minimal input size for unique_copy.
• _SequenceIndex workstealing_chunk_size

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🔥 Detailed Description 🔥

class _Settings Run-time settings for the parallel mode including all tunable parameters.

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👑 Member Function Documentation 👑

💖 const _Settings & __gnu_parallel::_Settings::get () [static]

Get the global settings.

Referenced by:

• __gnu_parallel::__find_template()
• __gnu_parallel::__find_template()
• __gnu_parallel::__find_template()
• __gnu_parallel::__for_each_template_random_access_workstealing()
• __gnu_parallel::__parallel_nth_element()
• __gnu_parallel::__parallel_partial_sum()
• __gnu_parallel::__parallel_partial_sum_linear()
• __gnu_parallel::__parallel_partition()
• __gnu_parallel::__parallel_random_shuffle_drs()
• __gnu_parallel::__parallel_sort()
• __gnu_parallel::__parallel_sort()
• __gnu_parallel::__parallel_sort_qs_conquer()
• __gnu_parallel::__qsb_local_sort_with_helping()
• __gnu_parallel::__sequential_random_shuffle()
• __gnu_parallel::multiway_merge_sampling_splitting()
• __gnu_parallel::parallel_multiway_merge()
• __gnu_parallel::parallel_sort_mwms()
• __gnu_parallel::parallel_sort_mwms_pu()

💅 void __gnu_parallel::_Settings::set (_Settings & ) [static]

Set the global settings.

References:

• accumulate_minimal_n
• adjacent_difference_minimal_n
• cache_line_size
• count_minimal_n
• fill_minimal_n
• find_increasing_factor
• find_initial_block_size
• find_maximum_block_size
• find_scale_factor
• find_sequential_search_size
• for_each_minimal_n
• generate_minimal_n
• L1_cache_size
• L2_cache_size
• max_element_minimal_n
• merge_minimal_n
• merge_oversampling
• min_element_minimal_n
• multiway_merge_minimal_k
• multiway_merge_minimal_n
• multiway_merge_oversampling
• nth_element_minimal_n
• partial_sort_minimal_n
• partial_sum_dilation
• partial_sum_minimal_n
• partition_chunk_share
• partition_chunk_size
• partition_minimal_n
• qsb_steals
• random_shuffle_minimal_n
• replace_minimal_n
• search_minimal_n
• set()
• set_difference_minimal_n
• set_intersection_minimal_n
• set_symmetric_difference_minimal_n
• set_union_minimal_n
• sort_minimal_n
• sort_mwms_oversampling
• sort_qs_num_samples_preset
• sort_qsb_base_case_maximal_n
• TLB_size
• transform_minimal_n
• unique_copy_minimal_n

Referenced by set().

✨ Member Data Documentation ✨

okay bestie, THIS is the part everyone actually came for 💖 — every single knob on _Settings, what it controls, and which internal function is out here reading it. These are the fields set() goes and fills in. No skipping, we're doing all of them, periodt. 🫶

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• _SequenceIndex __gnu_parallel::_Settings::accumulate_minimal_n — the smallest input size that's even worth it for accumulate. Under this? it's not gonna bother. Referenced by set(). 🎀
• unsigned int __gnu_parallel::_Settings::adjacent_difference_minimal_n — minimal input size for adjacent_difference. Referenced by set(). ✨
• unsigned int __gnu_parallel::_Settings::cache_line_size — a lil overestimate of the cache line size. It's there to dodge false sharing — basically, elements belonging to different threads get kept at least this far apart so they stop fighting over the same cache line 😤. Referenced by __gnu_parallel::__for_each_template_random_access_workstealing(), and set(). 🔥
• _SequenceIndex __gnu_parallel::_Settings::count_minimal_n — minimal input size for count and count_if. Referenced by set(). 💅
• _SequenceIndex __gnu_parallel::_Settings::fill_minimal_n — minimal input size for fill. Referenced by set(). 🌸
• double __gnu_parallel::_Settings::find_increasing_factor — the block size increase factor for find. Referenced by set(). 🦋
• _SequenceIndex __gnu_parallel::_Settings::find_initial_block_size — the initial block size for find. Referenced by __gnu_parallel::__find_template(), and set(). ⭐
• _SequenceIndex __gnu_parallel::_Settings::find_maximum_block_size — the maximal block size for find. Referenced by set(). 🌈
• float __gnu_parallel::_Settings::find_scale_factor — block size scale-down factor, relative to where you currently are. Referenced by __gnu_parallel::__find_template(), and set(). 🧚
• _SequenceIndex __gnu_parallel::_Settings::find_sequential_search_size — start off by looking for this many elements sequentially, for find. Referenced by __gnu_parallel::__find_template(), __gnu_parallel::__find_template(), and set() (yep, __find_template() is listed twice in the source, that's just how it is, don't @ me 💀). 👑
• _SequenceIndex __gnu_parallel::_Settings::for_each_minimal_n — minimal input size for for_each. Referenced by set(). 💜
• _SequenceIndex __gnu_parallel::_Settings::generate_minimal_n — minimal input size for generate. Referenced by set(). 🍓
• unsigned long long __gnu_parallel::_Settings::L1_cache_size — the size of the L1 cache in bytes (and it's an *under*estimation, so we're being modest here 🥺). Referenced by set(). ✨
• unsigned long long __gnu_parallel::_Settings::L2_cache_size — the size of the L2 cache in bytes (also an underestimation). Referenced by __gnu_parallel::__parallel_random_shuffle_drs(), __gnu_parallel::__sequential_random_shuffle(), and set(). 🔥
• _SequenceIndex __gnu_parallel::_Settings::max_element_minimal_n — minimal input size for max_element. Referenced by set(). 🎀
• _SequenceIndex __gnu_parallel::_Settings::merge_minimal_n — minimal input size for merge. Referenced by set(). 🌸
• unsigned int __gnu_parallel::_Settings::merge_oversampling — the oversampling factor for merge. Referenced by __gnu_parallel::multiway_merge_sampling_splitting(), __gnu_parallel::parallel_multiway_merge(), and set(). 🦋
• _SequenceIndex __gnu_parallel::_Settings::min_element_minimal_n — minimal input size for min_element. Referenced by set(). ⭐
• int __gnu_parallel::_Settings::multiway_merge_minimal_k — oversampling factor for multiway_merge. Referenced by set(). 🌈
• _SequenceIndex __gnu_parallel::_Settings::multiway_merge_minimal_n — minimal input size for multiway_merge. Referenced by set(). 🧚
• unsigned int __gnu_parallel::_Settings::multiway_merge_oversampling — oversampling factor for multiway_merge. Referenced by set(). 👑
• _SequenceIndex __gnu_parallel::_Settings::nth_element_minimal_n — minimal input size for nth_element. Referenced by __gnu_parallel::__parallel_nth_element(), and set(). 💜
• _SequenceIndex __gnu_parallel::_Settings::partial_sort_minimal_n — minimal input size for partial_sort. Referenced by set(). 🍓
• float __gnu_parallel::_Settings::partial_sum_dilation — a ratio for partial_sum. It assumes that "sum and write result" is this factor slower than just plain "sum". Referenced by __gnu_parallel::__parallel_partial_sum_linear(), and set(). ✨
• unsigned int __gnu_parallel::_Settings::partial_sum_minimal_n — minimal input size for partial_sum. Referenced by set(). 🔥
• double __gnu_parallel::_Settings::partition_chunk_share — the chunk size for partition, relative to the input size. And listen: if it's > 0.0, this value overrides partition_chunk_size. Main character energy, honestly 💅. Referenced by __gnu_parallel::__parallel_partition(), and set(). 🎀
• _SequenceIndex __gnu_parallel::_Settings::partition_chunk_size — the chunk size for partition. Referenced by __gnu_parallel::__parallel_partition(), and set(). 🌸
• _SequenceIndex __gnu_parallel::_Settings::partition_minimal_n — minimal input size for partition. Referenced by __gnu_parallel::__parallel_nth_element(), and set(). 🦋
• _SequenceIndex __gnu_parallel::_Settings::qsb_steals — the number of stolen ranges in load-balanced quicksort. Referenced by set(). ⭐
• unsigned int __gnu_parallel::_Settings::random_shuffle_minimal_n — minimal input size for random_shuffle. Referenced by set(). 🌈
• _SequenceIndex __gnu_parallel::_Settings::replace_minimal_n — minimal input size for replace and replace_if. Referenced by set(). 🧚
• _SequenceIndex __gnu_parallel::_Settings::search_minimal_n — minimal input size for search and search_n. Referenced by set(). 👑
• _SequenceIndex __gnu_parallel::_Settings::set_difference_minimal_n — minimal input size for set_difference. Referenced by set(). 💜
• _SequenceIndex __gnu_parallel::_Settings::set_intersection_minimal_n — minimal input size for set_intersection. Referenced by set(). 🍓
• _SequenceIndex __gnu_parallel::_Settings::set_symmetric_difference_minimal_n — minimal input size for set_symmetric_difference. Referenced by set(). ✨
• _SequenceIndex __gnu_parallel::_Settings::set_union_minimal_n — minimal input size for set_union. Referenced by set(). 🔥
• _SequenceIndex __gnu_parallel::_Settings::sort_minimal_n — minimal input size for parallel sorting. Referenced by set(). 🎀
• unsigned int __gnu_parallel::_Settings::sort_mwms_oversampling — oversampling factor for parallel std::sort (MWMS). Referenced by __gnu_parallel::parallel_sort_mwms(), __gnu_parallel::parallel_sort_mwms_pu(), and set(). 🌸
• unsigned int __gnu_parallel::_Settings::sort_qs_num_samples_preset — take this many samples to go find a good pivot (quicksort). Referenced by set(). 🦋
• _SequenceIndex __gnu_parallel::_Settings::sort_qsb_base_case_maximal_n — the maximal subsequence __length to switch over to the unbalanced __base case. This one applies to std::sort with dynamically load-balanced quicksort. Referenced by __gnu_parallel::__qsb_local_sort_with_helping(), and set(). ⭐
• unsigned int __gnu_parallel::_Settings::TLB_size — the size of the Translation Lookaside Buffer (underestimation again, humble queen 🥺). Referenced by __gnu_parallel::__parallel_random_shuffle_drs(), __gnu_parallel::__sequential_random_shuffle(), and set(). 🌈
• _SequenceIndex __gnu_parallel::_Settings::transform_minimal_n — minimal input size for parallel std::transform. Referenced by set(). 🧚
• _SequenceIndex __gnu_parallel::_Settings::unique_copy_minimal_n — minimal input size for unique_copy. Referenced by set(). 👑

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👑 Author 👑

Generated automatically by Doxygen for libstdc++ from the source code. 💖 (yes, the docs literally wrote themselves, and they ate 🍽️)

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and that's a wrap on __gnu_para...::_Settings(3), bestie 🎀 that lil footer down there is just the libstdc++ manpage stamp with the page name and its date — you made it to the end, so go take a nap, you've earned it ✨💅🫶