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Diffstat (limited to 'benchmarks/others/hopscotch_growth_policy.h')
| -rw-r--r-- | benchmarks/others/hopscotch_growth_policy.h | 346 |
1 files changed, 346 insertions, 0 deletions
diff --git a/benchmarks/others/hopscotch_growth_policy.h b/benchmarks/others/hopscotch_growth_policy.h new file mode 100644 index 00000000..8c9f9694 --- /dev/null +++ b/benchmarks/others/hopscotch_growth_policy.h @@ -0,0 +1,346 @@ +/** + * MIT License + * + * Copyright (c) 2018 Thibaut Goetghebuer-Planchon <[email protected]> + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in all + * copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ +#ifndef TSL_HOPSCOTCH_GROWTH_POLICY_H +#define TSL_HOPSCOTCH_GROWTH_POLICY_H + + +#include <algorithm> +#include <array> +#include <climits> +#include <cmath> +#include <cstddef> +#include <cstdint> +#include <iterator> +#include <limits> +#include <ratio> +#include <stdexcept> + + +/** + * Only activate tsl_hh_assert if TSL_DEBUG is defined. + * This way we avoid the performance hit when NDEBUG is not defined with assert as tsl_hh_assert is used a lot + * (people usually compile with "-O3" and not "-O3 -DNDEBUG"). + */ +#ifdef TSL_DEBUG +# define tsl_hh_assert(expr) assert(expr) +#else +# define tsl_hh_assert(expr) (static_cast<void>(0)) +#endif + + +/** + * If exceptions are enabled, throw the exception passed in parameter, otherwise call std::terminate. + */ +#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || (defined (_MSC_VER) && defined (_CPPUNWIND))) && !defined(TSL_NO_EXCEPTIONS) +# define TSL_HH_THROW_OR_TERMINATE(ex, msg) throw ex(msg) +#else +# define TSL_HH_NO_EXCEPTIONS +# ifdef NDEBUG +# define TSL_HH_THROW_OR_TERMINATE(ex, msg) std::terminate() +# else +# include <iostream> +# define TSL_HH_THROW_OR_TERMINATE(ex, msg) do { std::cerr << msg << std::endl; std::terminate(); } while(0) +# endif +#endif + + +namespace tsl { +namespace hh { + +/** + * Grow the hash table by a factor of GrowthFactor keeping the bucket count to a power of two. It allows + * the table to use a mask operation instead of a modulo operation to map a hash to a bucket. + * + * GrowthFactor must be a power of two >= 2. + */ +template<std::size_t GrowthFactor> +class power_of_two_growth_policy { +public: + /** + * Called on the hash table creation and on rehash. The number of buckets for the table is passed in parameter. + * This number is a minimum, the policy may update this value with a higher value if needed (but not lower). + * + * If 0 is given, min_bucket_count_in_out must still be 0 after the policy creation and + * bucket_for_hash must always return 0 in this case. + */ + explicit power_of_two_growth_policy(std::size_t& min_bucket_count_in_out) { + if(min_bucket_count_in_out > max_bucket_count()) { + TSL_HH_THROW_OR_TERMINATE(std::length_error, "The hash table exceeds its maximum size."); + } + + if(min_bucket_count_in_out > 0) { + min_bucket_count_in_out = round_up_to_power_of_two(min_bucket_count_in_out); + m_mask = min_bucket_count_in_out - 1; + } + else { + m_mask = 0; + } + } + + /** + * Return the bucket [0, bucket_count()) to which the hash belongs. + * If bucket_count() is 0, it must always return 0. + */ + std::size_t bucket_for_hash(std::size_t hash) const noexcept { + return hash & m_mask; + } + + /** + * Return the bucket count to use when the bucket array grows on rehash. + */ + std::size_t next_bucket_count() const { + if((m_mask + 1) > max_bucket_count() / GrowthFactor) { + TSL_HH_THROW_OR_TERMINATE(std::length_error, "The hash table exceeds its maximum size."); + } + + return (m_mask + 1) * GrowthFactor; + } + + /** + * Return the maximum number of buckets supported by the policy. + */ + std::size_t max_bucket_count() const { + // Largest power of two. + return (std::numeric_limits<std::size_t>::max() / 2) + 1; + } + + /** + * Reset the growth policy as if it was created with a bucket count of 0. + * After a clear, the policy must always return 0 when bucket_for_hash is called. + */ + void clear() noexcept { + m_mask = 0; + } + +private: + static std::size_t round_up_to_power_of_two(std::size_t value) { + if(is_power_of_two(value)) { + return value; + } + + if(value == 0) { + return 1; + } + + --value; + for(std::size_t i = 1; i < sizeof(std::size_t) * CHAR_BIT; i *= 2) { + value |= value >> i; + } + + return value + 1; + } + + static constexpr bool is_power_of_two(std::size_t value) { + return value != 0 && (value & (value - 1)) == 0; + } + +private: + static_assert(is_power_of_two(GrowthFactor) && GrowthFactor >= 2, "GrowthFactor must be a power of two >= 2."); + + std::size_t m_mask; +}; + + +/** + * Grow the hash table by GrowthFactor::num / GrowthFactor::den and use a modulo to map a hash + * to a bucket. Slower but it can be useful if you want a slower growth. + */ +template<class GrowthFactor = std::ratio<3, 2>> +class mod_growth_policy { +public: + explicit mod_growth_policy(std::size_t& min_bucket_count_in_out) { + if(min_bucket_count_in_out > max_bucket_count()) { + TSL_HH_THROW_OR_TERMINATE(std::length_error, "The hash table exceeds its maximum size."); + } + + if(min_bucket_count_in_out > 0) { + m_mod = min_bucket_count_in_out; + } + else { + m_mod = 1; + } + } + + std::size_t bucket_for_hash(std::size_t hash) const noexcept { + return hash % m_mod; + } + + std::size_t next_bucket_count() const { + if(m_mod == max_bucket_count()) { + TSL_HH_THROW_OR_TERMINATE(std::length_error, "The hash table exceeds its maximum size."); + } + + const double next_bucket_count = std::ceil(double(m_mod) * REHASH_SIZE_MULTIPLICATION_FACTOR); + if(!std::isnormal(next_bucket_count)) { + TSL_HH_THROW_OR_TERMINATE(std::length_error, "The hash table exceeds its maximum size."); + } + + if(next_bucket_count > double(max_bucket_count())) { + return max_bucket_count(); + } + else { + return std::size_t(next_bucket_count); + } + } + + std::size_t max_bucket_count() const { + return MAX_BUCKET_COUNT; + } + + void clear() noexcept { + m_mod = 1; + } + +private: + static constexpr double REHASH_SIZE_MULTIPLICATION_FACTOR = 1.0 * GrowthFactor::num / GrowthFactor::den; + static const std::size_t MAX_BUCKET_COUNT = + std::size_t(double( + std::numeric_limits<std::size_t>::max() / REHASH_SIZE_MULTIPLICATION_FACTOR + )); + + static_assert(REHASH_SIZE_MULTIPLICATION_FACTOR >= 1.1, "Growth factor should be >= 1.1."); + + std::size_t m_mod; +}; + + + +namespace detail { + +#if SIZE_MAX >= ULLONG_MAX +#define TSL_HH_NB_PRIMES 51 +#elif SIZE_MAX >= ULONG_MAX +#define TSL_HH_NB_PRIMES 40 +#else +#define TSL_HH_NB_PRIMES 23 +#endif + +static constexpr const std::array<std::size_t, TSL_HH_NB_PRIMES> PRIMES = {{ + 1u, 5u, 17u, 29u, 37u, 53u, 67u, 79u, 97u, 131u, 193u, 257u, 389u, 521u, 769u, 1031u, + 1543u, 2053u, 3079u, 6151u, 12289u, 24593u, 49157u, +#if SIZE_MAX >= ULONG_MAX + 98317ul, 196613ul, 393241ul, 786433ul, 1572869ul, 3145739ul, 6291469ul, 12582917ul, + 25165843ul, 50331653ul, 100663319ul, 201326611ul, 402653189ul, 805306457ul, 1610612741ul, + 3221225473ul, 4294967291ul, +#endif +#if SIZE_MAX >= ULLONG_MAX + 6442450939ull, 12884901893ull, 25769803751ull, 51539607551ull, 103079215111ull, 206158430209ull, + 412316860441ull, 824633720831ull, 1649267441651ull, 3298534883309ull, 6597069766657ull, +#endif +}}; + +template<unsigned int IPrime> +static constexpr std::size_t mod(std::size_t hash) { return hash % PRIMES[IPrime]; } + +// MOD_PRIME[iprime](hash) returns hash % PRIMES[iprime]. This table allows for faster modulo as the +// compiler can optimize the modulo code better with a constant known at the compilation. +static constexpr const std::array<std::size_t(*)(std::size_t), TSL_HH_NB_PRIMES> MOD_PRIME = {{ + &mod<0>, &mod<1>, &mod<2>, &mod<3>, &mod<4>, &mod<5>, &mod<6>, &mod<7>, &mod<8>, &mod<9>, &mod<10>, + &mod<11>, &mod<12>, &mod<13>, &mod<14>, &mod<15>, &mod<16>, &mod<17>, &mod<18>, &mod<19>, &mod<20>, + &mod<21>, &mod<22>, +#if SIZE_MAX >= ULONG_MAX + &mod<23>, &mod<24>, &mod<25>, &mod<26>, &mod<27>, &mod<28>, &mod<29>, &mod<30>, &mod<31>, &mod<32>, + &mod<33>, &mod<34>, &mod<35>, &mod<36>, &mod<37> , &mod<38>, &mod<39>, +#endif +#if SIZE_MAX >= ULLONG_MAX + &mod<40>, &mod<41>, &mod<42>, &mod<43>, &mod<44>, &mod<45>, &mod<46>, &mod<47>, &mod<48>, &mod<49>, + &mod<50>, +#endif +}}; + +} + +/** + * Grow the hash table by using prime numbers as bucket count. Slower than tsl::hh::power_of_two_growth_policy in + * general but will probably distribute the values around better in the buckets with a poor hash function. + * + * To allow the compiler to optimize the modulo operation, a lookup table is used with constant primes numbers. + * + * With a switch the code would look like: + * \code + * switch(iprime) { // iprime is the current prime of the hash table + * case 0: hash % 5ul; + * break; + * case 1: hash % 17ul; + * break; + * case 2: hash % 29ul; + * break; + * ... + * } + * \endcode + * + * Due to the constant variable in the modulo the compiler is able to optimize the operation + * by a series of multiplications, substractions and shifts. + * + * The 'hash % 5' could become something like 'hash - (hash * 0xCCCCCCCD) >> 34) * 5' in a 64 bits environment. + */ +class prime_growth_policy { +public: + explicit prime_growth_policy(std::size_t& min_bucket_count_in_out) { + auto it_prime = std::lower_bound(detail::PRIMES.begin(), + detail::PRIMES.end(), min_bucket_count_in_out); + if(it_prime == detail::PRIMES.end()) { + TSL_HH_THROW_OR_TERMINATE(std::length_error, "The hash table exceeds its maximum size."); + } + + m_iprime = static_cast<unsigned int>(std::distance(detail::PRIMES.begin(), it_prime)); + if(min_bucket_count_in_out > 0) { + min_bucket_count_in_out = *it_prime; + } + else { + min_bucket_count_in_out = 0; + } + } + + std::size_t bucket_for_hash(std::size_t hash) const noexcept { + return detail::MOD_PRIME[m_iprime](hash); + } + + std::size_t next_bucket_count() const { + if(m_iprime + 1 >= detail::PRIMES.size()) { + TSL_HH_THROW_OR_TERMINATE(std::length_error, "The hash table exceeds its maximum size."); + } + + return detail::PRIMES[m_iprime + 1]; + } + + std::size_t max_bucket_count() const { + return detail::PRIMES.back(); + } + + void clear() noexcept { + m_iprime = 0; + } + +private: + unsigned int m_iprime; + + static_assert(std::numeric_limits<decltype(m_iprime)>::max() >= detail::PRIMES.size(), + "The type of m_iprime is not big enough."); +}; + +} +} + +#endif |