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Add a second level of follow-up moves
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STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 6438 W: 1229 L: 1077 D: 4132

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 4000 W: 605 L: 473 D: 2922

bench: 7378965

Resolves #636
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@loco-loco @zamar
loco-loco authored and zamar committed Apr 17, 2016
1 parent 7eaea38 commit ec6aab0
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Showing 4 changed files with 72 additions and 51 deletions.
33 changes: 20 additions & 13 deletions src/movepick.cpp
View file
Expand Up @@ -67,22 +67,21 @@ namespace {
/// search captures, promotions, and some checks) and how important good move
/// ordering is at the current node.

MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h,
const CounterMoveStats& cmh, const CounterMoveStats& fmh,
Move cm, Search::Stack* s)
: pos(p), history(h), counterMoveHistory(&cmh),
followupMoveHistory(&fmh), ss(s), countermove(cm), depth(d) {
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, Search::Stack* s)
: pos(p), ss(s), depth(d) {

assert(d > DEPTH_ZERO);

Square prevSq = to_sq((ss-1)->currentMove);
countermove = pos.this_thread()->counterMoves[pos.piece_on(prevSq)][prevSq];

stage = pos.checkers() ? EVASION : MAIN_SEARCH;
ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
endMoves += (ttMove != MOVE_NONE);
}

MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
const HistoryStats& h, Square s)
: pos(p), history(h) {
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, Square s)
: pos(p) {

assert(d <= DEPTH_ZERO);

Expand All @@ -106,8 +105,8 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
endMoves += (ttMove != MOVE_NONE);
}

MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, Value th)
: pos(p), history(h), threshold(th) {
MovePicker::MovePicker(const Position& p, Move ttm, Value th)
: pos(p), threshold(th) {

assert(!pos.checkers());

Expand Down Expand Up @@ -142,17 +141,25 @@ void MovePicker::score<CAPTURES>() {
template<>
void MovePicker::score<QUIETS>() {

const HistoryStats& history = pos.this_thread()->history;

const CounterMoveStats* cm = (ss-1)->counterMoves;
const CounterMoveStats* fm = (ss-2)->counterMoves;
const CounterMoveStats* f2 = (ss-4)->counterMoves;

for (auto& m : *this)
m.value = history[pos.moved_piece(m)][to_sq(m)]
+ (*counterMoveHistory )[pos.moved_piece(m)][to_sq(m)]
+ (*followupMoveHistory)[pos.moved_piece(m)][to_sq(m)];
m.value = history[pos.moved_piece(m)][to_sq(m)]
+ (cm ? (*cm)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO)
+ (fm ? (*fm)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO)
+ (f2 ? (*f2)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO);
}

template<>
void MovePicker::score<EVASIONS>() {
// Try winning and equal captures ordered by MVV/LVA, then non-captures ordered
// by history value, then bad captures and quiet moves with a negative SEE ordered
// by SEE value.
const HistoryStats& history = pos.this_thread()->history;
Value see;

for (auto& m : *this)
Expand Down
12 changes: 4 additions & 8 deletions src/movepick.h
View file
Expand Up @@ -79,10 +79,9 @@ class MovePicker {
MovePicker(const MovePicker&) = delete;
MovePicker& operator=(const MovePicker&) = delete;

MovePicker(const Position&, Move, const HistoryStats&, Value);
MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
MovePicker(const Position&, Move, Depth, const HistoryStats&,
const CounterMoveStats&, const CounterMoveStats&, Move, Search::Stack*);
MovePicker(const Position&, Move, Value);
MovePicker(const Position&, Move, Depth, Square);
MovePicker(const Position&, Move, Depth, Search::Stack*);

Move next_move();

Expand All @@ -93,10 +92,7 @@ class MovePicker {
ExtMove* end() { return endMoves; }

const Position& pos;
const HistoryStats& history;
const CounterMoveStats* counterMoveHistory;
const CounterMoveStats* followupMoveHistory;
Search::Stack* ss;
const Search::Stack* ss;
Move countermove;
Depth depth;
Move ttMove;
Expand Down
74 changes: 44 additions & 30 deletions src/search.cpp
View file
Expand Up @@ -380,12 +380,12 @@ void MainThread::search() {

void Thread::search() {

Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2)
Stack stack[MAX_PLY+7], *ss = stack+5; // To allow referencing (ss-5) and (ss+2)
Value bestValue, alpha, beta, delta;
Move easyMove = MOVE_NONE;
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);

std::memset(ss-2, 0, 5 * sizeof(Stack));
std::memset(ss-5, 0, 8 * sizeof(Stack));

bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
Expand Down Expand Up @@ -657,6 +657,7 @@ namespace {
assert(0 <= ss->ply && ss->ply < MAX_PLY);

ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
ss->counterMoves = nullptr;
(ss+1)->skipEarlyPruning = false;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;

Expand Down Expand Up @@ -780,6 +781,7 @@ namespace {
&& pos.non_pawn_material(pos.side_to_move()))
{
ss->currentMove = MOVE_NULL;
ss->counterMoves = nullptr;

assert(eval - beta >= 0);

Expand Down Expand Up @@ -828,13 +830,14 @@ namespace {
assert((ss-1)->currentMove != MOVE_NONE);
assert((ss-1)->currentMove != MOVE_NULL);

MovePicker mp(pos, ttMove, thisThread->history, PieceValue[MG][pos.captured_piece_type()]);
MovePicker mp(pos, ttMove, PieceValue[MG][pos.captured_piece_type()]);
CheckInfo ci(pos);

while ((move = mp.next_move()) != MOVE_NONE)
if (pos.legal(move, ci.pinned))
{
ss->currentMove = move;
ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)];
pos.do_move(move, st, pos.gives_check(move, ci));
value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
Expand All @@ -860,12 +863,9 @@ namespace {
moves_loop: // When in check search starts from here

Square prevSq = to_sq((ss-1)->currentMove);
Square ownPrevSq = to_sq((ss-2)->currentMove);
Move cm = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
const CounterMoveStats& cmh = CounterMoveHistory[pos.piece_on(prevSq)][prevSq];
const CounterMoveStats& fmh = CounterMoveHistory[pos.piece_on(ownPrevSq)][ownPrevSq];

MovePicker mp(pos, ttMove, depth, thisThread->history, cmh, fmh, cm, ss);
MovePicker mp(pos, ttMove, depth, ss);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
improving = ss->staticEval >= (ss-2)->staticEval
Expand Down Expand Up @@ -992,6 +992,7 @@ namespace {
}

ss->currentMove = move;
ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)];

// Step 14. Make the move
pos.do_move(move, st, givesCheck);
Expand Down Expand Up @@ -1153,13 +1154,17 @@ namespace {
&& !bestMove
&& !inCheck
&& !pos.captured_piece_type()
&& is_ok((ss - 1)->currentMove)
&& is_ok((ss - 2)->currentMove))
&& is_ok((ss-1)->currentMove))
{
Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1);
Square prevPrevSq = to_sq((ss - 2)->currentMove);
CounterMoveStats& prevCmh = CounterMoveHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
prevCmh.update(pos.piece_on(prevSq), prevSq, bonus);
if ((ss-2)->counterMoves)
(ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus);

if ((ss-3)->counterMoves)
(ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus);

if ((ss-5)->counterMoves)
(ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus);
}

tte->save(posKey, value_to_tt(bestValue, ss->ply),
Expand Down Expand Up @@ -1280,7 +1285,7 @@ namespace {
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
// be generated.
MovePicker mp(pos, ttMove, depth, pos.this_thread()->history, to_sq((ss-1)->currentMove));
MovePicker mp(pos, ttMove, depth, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);

// Loop through the moves until no moves remain or a beta cutoff occurs
Expand Down Expand Up @@ -1434,42 +1439,51 @@ namespace {
Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1);

Square prevSq = to_sq((ss-1)->currentMove);
Square ownPrevSq = to_sq((ss-2)->currentMove);
CounterMoveStats& cmh = CounterMoveHistory[pos.piece_on(prevSq)][prevSq];
CounterMoveStats& fmh = CounterMoveHistory[pos.piece_on(ownPrevSq)][ownPrevSq];
CounterMoveStats* cmh = (ss-1)->counterMoves;
CounterMoveStats* fmh = (ss-2)->counterMoves;
CounterMoveStats* fmh2 = (ss-4)->counterMoves;
Thread* thisThread = pos.this_thread();

thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus);

if (is_ok((ss-1)->currentMove))
if (cmh)
{
thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move);
cmh.update(pos.moved_piece(move), to_sq(move), bonus);
cmh->update(pos.moved_piece(move), to_sq(move), bonus);
}

if (is_ok((ss-2)->currentMove))
fmh.update(pos.moved_piece(move), to_sq(move), bonus);
if (fmh)
fmh->update(pos.moved_piece(move), to_sq(move), bonus);

if (fmh2)
fmh2->update(pos.moved_piece(move), to_sq(move), bonus);

// Decrease all the other played quiet moves
for (int i = 0; i < quietsCnt; ++i)
{
thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);

if (is_ok((ss-1)->currentMove))
cmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
if (cmh)
cmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);

if (is_ok((ss-2)->currentMove))
fmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
if (fmh)
fmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);

if (fmh2)
fmh2->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
}

// Extra penalty for a quiet TT move in previous ply when it gets refuted
if ( (ss-1)->moveCount == 1
&& !pos.captured_piece_type()
&& is_ok((ss-2)->currentMove))
if ((ss-1)->moveCount == 1 && !pos.captured_piece_type())
{
Square prevPrevSq = to_sq((ss-2)->currentMove);
CounterMoveStats& prevCmh = CounterMoveHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
prevCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY);
if ((ss-2)->counterMoves)
(ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY);

if ((ss-3)->counterMoves)
(ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY);

if ((ss-5)->counterMoves)
(ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY);
}
}

Expand Down
4 changes: 4 additions & 0 deletions src/search.h
View file
Expand Up @@ -28,6 +28,9 @@
#include "position.h"
#include "types.h"

template<typename T, bool CM> struct Stats;
typedef Stats<Value, true> CounterMoveStats;

namespace Search {

/// Stack struct keeps track of the information we need to remember from nodes
Expand All @@ -43,6 +46,7 @@ struct Stack {
Value staticEval;
bool skipEarlyPruning;
int moveCount;
CounterMoveStats* counterMoves;
};

/// RootMove struct is used for moves at the root of the tree. For each root move
Expand Down

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