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759b3c79cf
To more clearly distinguish them from "const" local variables, this patch defines compile-time local constants as constexpr. This is consistent with the definition of PvNode as constexpr in search() and qsearch(). It also makes the code more robust, since the compiler will now check that those constants are indeed compile-time constants. We can go even one step further and define all the evaluation and search compile-time constants as constexpr. In generate_castling() I replaced "K" with "step", since K was incorrectly capitalised (in the Chess960 case). In timeman.cpp I had to make the non-local constants MaxRatio and StealRatio constepxr, since otherwise gcc would complain when calculating TMaxRatio and TStealRatio. (Strangely, I did not have to make Is64Bit constexpr even though it is used in ucioption.cpp in the calculation of constexpr MaxHashMB.) I have renamed PieceCount to pieceCount in material.h, since the values of the array are not compile-time constants. Some compile-time constants in tbprobe.cpp were overlooked. Sides and MaxFile are not compile-time constants, so were renamed to sides and maxFile. Non-functional change.
122 lines
3.7 KiB
C++
122 lines
3.7 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef TT_H_INCLUDED
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#define TT_H_INCLUDED
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#include "misc.h"
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#include "types.h"
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/// TTEntry struct is the 10 bytes transposition table entry, defined as below:
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///
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/// key 16 bit
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/// move 16 bit
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/// value 16 bit
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/// eval value 16 bit
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/// generation 6 bit
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/// bound type 2 bit
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/// depth 8 bit
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struct TTEntry {
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Move move() const { return (Move )move16; }
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Value value() const { return (Value)value16; }
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Value eval() const { return (Value)eval16; }
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Depth depth() const { return (Depth)(depth8 * int(ONE_PLY)); }
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Bound bound() const { return (Bound)(genBound8 & 0x3); }
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void save(Key k, Value v, Bound b, Depth d, Move m, Value ev, uint8_t g) {
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assert(d / ONE_PLY * ONE_PLY == d);
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// Preserve any existing move for the same position
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if (m || (k >> 48) != key16)
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move16 = (uint16_t)m;
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// Don't overwrite more valuable entries
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if ( (k >> 48) != key16
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|| d / ONE_PLY > depth8 - 4
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/* || g != (genBound8 & 0xFC) // Matching non-zero keys are already refreshed by probe() */
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|| b == BOUND_EXACT)
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{
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key16 = (uint16_t)(k >> 48);
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value16 = (int16_t)v;
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eval16 = (int16_t)ev;
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genBound8 = (uint8_t)(g | b);
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depth8 = (int8_t)(d / ONE_PLY);
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}
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}
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private:
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friend class TranspositionTable;
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uint16_t key16;
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uint16_t move16;
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int16_t value16;
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int16_t eval16;
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uint8_t genBound8;
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int8_t depth8;
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};
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/// A TranspositionTable consists of a power of 2 number of clusters and each
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/// cluster consists of ClusterSize number of TTEntry. Each non-empty entry
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/// contains information of exactly one position. The size of a cluster should
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/// divide the size of a cache line size, to ensure that clusters never cross
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/// cache lines. This ensures best cache performance, as the cacheline is
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/// prefetched, as soon as possible.
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class TranspositionTable {
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static constexpr int CacheLineSize = 64;
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static constexpr int ClusterSize = 3;
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struct Cluster {
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TTEntry entry[ClusterSize];
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char padding[2]; // Align to a divisor of the cache line size
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};
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static_assert(CacheLineSize % sizeof(Cluster) == 0, "Cluster size incorrect");
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public:
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~TranspositionTable() { free(mem); }
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void new_search() { generation8 += 4; } // Lower 2 bits are used by Bound
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uint8_t generation() const { return generation8; }
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TTEntry* probe(const Key key, bool& found) const;
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int hashfull() const;
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void resize(size_t mbSize);
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void clear();
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// The 32 lowest order bits of the key are used to get the index of the cluster
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TTEntry* first_entry(const Key key) const {
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return &table[(uint32_t(key) * uint64_t(clusterCount)) >> 32].entry[0];
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}
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private:
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size_t clusterCount;
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Cluster* table;
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void* mem;
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uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
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};
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extern TranspositionTable TT;
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#endif // #ifndef TT_H_INCLUDED
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