Merge pull request #16 from bakwc/speedOptimize

Improved performance

Author: bakwc

README.md

@@ -42,7 +42,7 @@ JamSpell is a spell checking library with following features:
     <td>79.53%</td>
     <td>84.10%</td>
     <td>0.64%</td>
-    <td>1833</td>
+    <td>4854</td>
   </tr>
   <tr>
     <td>Norvig</td>
@@ -103,7 +103,7 @@ To ensure that our model is not too overfitted for wikipedia+news we checked it
     <td>72.03%</td>
     <td>79.73%</td>
     <td>0.50%</td>
-    <td>1764</td>
+    <td>5524</td>
   </tr>
   <tr>
     <td>Norvig</td>

contrib/CMakeLists.txt

@@ -3,4 +3,4 @@ add_subdirectory(handypack)
 add_subdirectory(phf)
 add_subdirectory(cityhash)
 add_subdirectory(bloom)
-
+add_subdirectory(tsl)

contrib/tsl/CMakeLists.txt

@@ -0,0 +1 @@
+add_library(tsl robin_map.cpp robin_map.h robin_hash.h robin_set.h)

contrib/tsl/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2017 Tessil
+
+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.

contrib/tsl/robin_growth_policy.h

@@ -0,0 +1,270 @@
+/**
+ * MIT License
+ * 
+ * Copyright (c) 2017 Tessil
+ * 
+ * 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_ROBIN_GROWTH_POLICY_H
+#define TSL_ROBIN_GROWTH_POLICY_H 
+
+
+#include <algorithm>
+#include <array>
+#include <climits>
+#include <cmath>
+#include <cstddef>
+#include <iterator>
+#include <limits>
+#include <ratio>
+#include <stdexcept>
+
+
+namespace tsl {
+namespace rh {
+    
+/**
+ * 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).
+     */
+    power_of_two_growth_policy(std::size_t& min_bucket_count_in_out) {
+        if(min_bucket_count_in_out > max_bucket_count()) {
+            throw std::length_error("The hash table exceeds its maxmimum size.");
+        }
+        
+        static_assert(MIN_BUCKETS_SIZE > 0, "MIN_BUCKETS_SIZE must be > 0.");
+        const std::size_t min_bucket_count = MIN_BUCKETS_SIZE;
+        
+        min_bucket_count_in_out = std::max(min_bucket_count, min_bucket_count_in_out);
+        min_bucket_count_in_out = round_up_to_power_of_two(min_bucket_count_in_out);
+        m_mask = min_bucket_count_in_out - 1;
+    }
+    
+    /**
+     * Return the bucket [0, bucket_count()) to which the hash belongs.
+     */
+    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) {
+            throw std::length_error("The hash table exceeds its maxmimum 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;
+    }
+    
+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;
+    }
+    
+protected:
+    static const std::size_t MIN_BUCKETS_SIZE = 2;
+    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 usefull if you want a slower growth.
+ */
+template<class GrowthFactor = std::ratio<3, 2>>
+class mod_growth_policy {
+public:
+    mod_growth_policy(std::size_t& min_bucket_count_in_out) {
+        if(min_bucket_count_in_out > max_bucket_count()) {
+            throw std::length_error("The hash table exceeds its maxmimum size.");
+        }
+        
+        static_assert(MIN_BUCKETS_SIZE > 0, "MIN_BUCKETS_SIZE must be > 0.");
+        const std::size_t min_bucket_count = MIN_BUCKETS_SIZE;
+        
+        min_bucket_count_in_out = std::max(min_bucket_count, min_bucket_count_in_out);
+        m_bucket_count = min_bucket_count_in_out;
+    }
+    
+    std::size_t bucket_for_hash(std::size_t hash) const noexcept {
+        return hash % m_bucket_count;
+    }
+    
+    std::size_t next_bucket_count() const {
+        if(m_bucket_count == max_bucket_count()) {
+            throw std::length_error("The hash table exceeds its maxmimum size.");
+        }
+        
+        const double next_bucket_count = std::ceil(double(m_bucket_count) * REHASH_SIZE_MULTIPLICATION_FACTOR);
+        if(!std::isnormal(next_bucket_count)) {
+            throw std::length_error("The hash table exceeds its maxmimum 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;
+    }
+    
+private:
+    static const std::size_t MIN_BUCKETS_SIZE = 2;
+    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_bucket_count;
+};
+
+
+
+namespace detail {
+
+static constexpr const std::array<std::size_t, 39> PRIMES = {{
+    5ul, 17ul, 29ul, 37ul, 53ul, 67ul, 79ul, 97ul, 131ul, 193ul, 257ul, 389ul, 521ul, 769ul, 1031ul, 1543ul, 2053ul, 
+    3079ul, 6151ul, 12289ul, 24593ul, 49157ul, 98317ul, 196613ul, 393241ul, 786433ul, 1572869ul, 3145739ul, 
+    6291469ul, 12582917ul, 25165843ul, 50331653ul, 100663319ul, 201326611ul, 402653189ul, 805306457ul, 
+    1610612741ul, 3221225473ul, 4294967291ul
+}};
+
+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), 39> 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>, &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>
+}};
+
+}
+
+/**
+ * Grow the hash table by using prime numbers as bucket count. Slower than tsl::rh::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 environement.
+ */
+class prime_growth_policy {
+public:
+    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()) {
+            throw std::length_error("The hash table exceeds its maxmimum size.");
+        }
+        
+        m_iprime = static_cast<unsigned int>(std::distance(detail::PRIMES.begin(), it_prime));
+        min_bucket_count_in_out = *it_prime;
+    }
+    
+    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()) {
+            throw std::length_error("The hash table exceeds its maxmimum size.");
+        }
+        
+        return detail::PRIMES[m_iprime + 1];
+    }   
+    
+    std::size_t max_bucket_count() const {
+        return detail::PRIMES.back();
+    }
+    
+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