814ec7c2d0
* src/misc/hash.hh (ptr_hash): Use knuth32_hash. * src/tgba/tgbabddconcretefactory.hh (tgba_bdd_concrete_factory): Use ltl::formula_ptr_hash for acc_map_.
65 lines
2.1 KiB
C++
65 lines
2.1 KiB
C++
// Copyright (C) 2004, 2005 Laboratoire d'Informatique de Paris 6 (LIP6),
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// département Systèmes Répartis Coopératifs (SRC), Université Pierre
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// et Marie Curie.
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//
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// This file is part of Spot, a model checking library.
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//
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// Spot is free software; you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// Spot is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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// License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Spot; see the file COPYING. If not, write to the Free
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// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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// 02111-1307, USA.
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#ifndef SPOT_MISC_HASHFUNC_HH
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# define SPOT_MISC_HASHFUNC_HH
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# include <cstddef>
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namespace spot
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{
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/// \addtogroup hash_funcs Hashing functions
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/// \ingroup misc_tools
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/// @{
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/// \brief Thomas Wang's 32 bit hash function.
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///
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/// Hash an integer amongst the integers.
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/// http://www.concentric.net/~Ttwang/tech/inthash.htm
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inline size_t
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wang32_hash(size_t key)
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{
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// We assume that size_t has at least 32bits.
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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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/// \brief Knuth's Multiplicative hash function.
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///
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/// This function is suitable for hashing values whose
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/// high order bits do not vary much (ex. addresses of
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/// memory objects). Prefer spot::wang32_hash() otherwise.
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/// http://www.concentric.net/~Ttwang/tech/addrhash.htm
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inline size_t
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knuth32_hash(size_t key)
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{
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// 2654435761 is the golden ratio of 2^32. The right shift of 3
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// bits assumes that all objects are aligned on a 8 byte boundary.
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return (key >> 3) * 2654435761U;
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}
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/// @}
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}
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#endif // SPOT_MISC_HASHFUNC_HH
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