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https://github.com/SerenityOS/serenity
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4e50079f36
Instead of each hash bucket being a SinglyLinkedList, switch to using closed hashing (open addressing). Buckets are chained together via double hashing (hashing the hash until we find an unused bucket.) This greatly reduces malloc traffic, since each added element no longer allocates a new linked list node. Appears performance neutral on test-js. Can definitely be tuned and could use proper management of load factor, etc.
76 lines
2.3 KiB
C
76 lines
2.3 KiB
C
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "Types.h"
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inline unsigned int_hash(u32 key)
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{
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key += ~(key << 15);
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key ^= (key >> 10);
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key += (key << 3);
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key ^= (key >> 6);
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key += ~(key << 11);
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key ^= (key >> 16);
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return key;
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}
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inline unsigned double_hash(u32 key)
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{
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key = ~key + (key >> 23);
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key ^= (key << 12);
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key ^= (key >> 7);
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key ^= (key << 2);
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key ^= (key >> 20);
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return key;
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}
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inline unsigned pair_int_hash(u32 key1, u32 key2)
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{
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return int_hash((int_hash(key1) * 209) ^ (int_hash(key2 * 413)));
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}
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inline unsigned u64_hash(u64 key)
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{
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u32 first = key & 0xFFFFFFFF;
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u32 last = key >> 32;
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return pair_int_hash(first, last);
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}
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inline unsigned ptr_hash(FlatPtr ptr)
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{
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if constexpr (sizeof(ptr) == 8)
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return u64_hash((u64)ptr);
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else
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return int_hash((u32)ptr);
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}
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inline unsigned ptr_hash(const void* ptr)
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{
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return ptr_hash((FlatPtr)(ptr));
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}
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