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alphabeta.d
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import tango.core.Memory;
import tango.core.sync.Mutex;
import tango.util.Convert;
import goalsearch;
import logging;
import position;
import staticeval;
import trapmoves;
static const int MAX_EVAL_SCORE = 63979;
static const int MIN_WIN_SCORE = 63980;
static const int WIN_SCORE = 64000;
static const int MAX_SCORE = 65000;
static const int MIN_SCORE = -MAX_SCORE;
static const int ABORT_SCORE = MAX_SCORE+100;
enum SType { EXACT, ALPHA, BETA }
struct TTNode
{
ulong zobrist;
int depth;
int score;
SType type;
Step beststep;
bool aged;
void set(Position pos, int newdepth, int newscore, SType newtype, Step newbstep)
{
if (aged
|| depth < newdepth
|| zobrist == pos.zobrist)
{
zobrist = pos.zobrist;
depth = newdepth;
score = newscore;
type = newtype;
beststep = newbstep;
aged = false;
}
}
}
class TransTable
{
Logger log;
TTNode[] store;
long hits, miss, collisions;
this (Logger l, int size)
{
log = l;
set_size(size);
hits = miss = collisions = 0;
}
void set_size(int size)
{
store.length = 0;
store.length = (size*1024*1024) / TTNode.sizeof;
store.length = store.length < 1 ? 1 : store.length;
GC.setAttr(cast(void*)store, GC.BlkAttr.NO_SCAN);
age();
log.log("Set transposition table size to {}MB ({} entries)", size, store.length);
}
TTNode* get(Position pos)
{
int key = pos.zobrist % store.length;
TTNode* node = &store[key];
if (store[key].zobrist != pos.zobrist)
{
key = (key + 1) % store.length;
if (store[key].zobrist == pos.zobrist)
{
node = &store[key];
} else {
if (!node.aged && node.depth > store[key].depth)
{
node = &store[key];
}
key = (key + 1) % store.length;
if (store[key].zobrist == pos.zobrist)
{
node = &store[key];
} else {
if (!node.aged && node.depth > store[key].depth)
{
node = &store[key];
}
key = (key + 1) % store.length;
if (store[key].zobrist == pos.zobrist
|| (!node.aged && node.depth > store[key].depth))
{
node = &store[key];
}
}
}
}
if (node.zobrist == pos.zobrist)
{
hits += 1;
}
else if (node.aged)
{
miss += 1;
} else {
collisions += 1;
}
return node;
}
void age()
{
for (int i=0; i < store.length; i++)
{
store[i].aged = true;
}
}
}
class HistoryHeuristic
{
uint[64][64][2] score;
uint[2] pass_score;
uint get_score(Position pos, Step step)
{
if (step.frombit == INV_STEP)
return pass_score[pos.side];
return score[pos.side][step.fromix][step.toix];
}
void update(Position pos, Step step, int depth)
{
if (step.frombit == INV_STEP)
pass_score[pos.side] += depth + 1;
else
score[pos.side][step.fromix][step.toix] += depth + 1;
}
void age()
{
for (int s=0; s < 2; s++)
{
for (int f=0; f < 64; f++)
{
for (int t=0; t < 64; t++)
{
score[s][f][t] /= 10;
}
}
pass_score[s] /= 10;
}
}
}
class KillerHeuristic
{
const static int MAX_HEIGHT = 20;
Step[2][2][MAX_HEIGHT] steps;
uint[64][64][2][MAX_HEIGHT] history;
uint[2][2][MAX_HEIGHT] max_history;
void set_killer(int height, Side side, Step step)
{
if (height >= MAX_HEIGHT)
return;
int step_history = history[height][side][step.fromix][step.toix]++;
if (step_history > max_history[height][side][0])
{
Step* first = &steps[height][side][0];
if (*first != step)
{
if (first.frombit != 0 || first.tobit != 0)
{
steps[height][side][1] = *first;
max_history[height][side][1] = max_history[height][side][0];
}
*first = step;
}
max_history[height][side][0] = step_history;
} else if (step_history > max_history[height][side][1])
{
if (steps[height][side][1] != step)
{
steps[height][side][1] = step;
}
max_history[height][side][1] = step_history;
}
}
void age()
{
for (int d=0; d < MAX_HEIGHT; d++)
{
for (int s=0; s < 2; s++)
{
for (int n=0; n < 2; n++)
{
max_history[d][s][n] = 0;
steps[d][s][n].clear();
}
for (int f=0; f < 64; f++)
{
for (int t=0; t < 64; t++)
{
history[d][s][f][t] = 0;
}
}
}
}
}
}
class StepSorter
{
private static Mutex cache_lock;
private static StepSorter[] reserve;
private static int reservesize;
static this()
{
cache_lock = new Mutex();
}
static StepSorter allocate(ABSearch s, int d, Position p, Step* b, Step* l)
{
synchronized (cache_lock)
{
if (reservesize)
{
reservesize--;
StepSorter ss = reserve[reservesize];
reserve[reservesize] = null;
ss.init(s, d, p, b, l);
return ss;
}
}
return new StepSorter(s, d, p, b, l);
}
static void free(StepSorter s)
{
synchronized (cache_lock)
{
if (reserve.length == reservesize)
{
reserve.length = (reserve.length+1) * 2;
}
reserve[reservesize++] = s;
}
}
static bool use_killers = true;
static bool use_history = true;
static bool capture_first = true;
static bool prune_unrelated = true;
ABSearch parent;
int height;
Position pos;
StepList steps;
Step best;
bool remove_unrelated;
Step* last;
private ulong last_tneighbors;
StepList capture_steps;
bool captures_generated;
int capture_num;
private ulong considered[64];
int num;
int stage;
int history_num;
int sub_ix;
this(ABSearch s, int d, Position p, Step* b, Step* l)
{
init(s, d, p, b, l);
}
void init(ABSearch s, int h, Position p, Step* b, Step* l)
{
parent = s;
height = h;
pos = p;
if (steps is null)
steps = StepList.allocate();
else
steps.clear();
p.get_steps(steps);
if (b !is null)
{
best = *b;
} else {
best.clear();
}
last = l;
if (last !is null)
last_tneighbors = neighbors_of(last.tobit);
if (prune_unrelated
&& pos.stepsLeft == 3
&& !pos.inpush
&& last !is null)
remove_unrelated = true;
else
remove_unrelated = false;
num = 0;
stage = 0;
captures_generated = 0;
history_num = 0;
sub_ix = 0;
for (int i=0; i < 64; i++)
considered[i] = 0UL;
}
private bool is_related(Step* s)
{
// using this to check only the second step in a move still misses
// some 3 step combos where the 3rd step depends on the first 2 steps
// but neither of the first two depend on each other
ulong to = s.tobit;
ulong from = s.frombit;
if (from == INV_STEP)
return false;
// Allow a step if:
// Piece steps into last from
// Same piece as last step
// Last step supported this step onto a trap
// Last step was to a neighbor of this from
// Last step allowed this piece to step away from a trap
if ((((to | from) & (last.tobit | last_tneighbors))
&& ((to == last.frombit) || (last.tobit == from)
|| ((to & TRAPS & last_tneighbors)
&& !(pos.placement[pos.side]
& neighbors_of(to)
& ~from & ~last.tobit))
|| (from & last_tneighbors)))
|| (last_tneighbors & neighbors_of(from) & TRAPS
& pos.placement[pos.side])
|| ((last.frombit & TRAPS)
&& (from & neighbors_of(last.frombit)
& pos.placement[pos.side])
&& !(neighbors_of(last.frombit)
& pos.placement[pos.side]
& ~from & ~last.tobit)))
return true;
return false;
}
Step* next_step()
{
if (num >= steps.numsteps)
{
return null;
}
Step* step;
switch (stage)
{
case 0:
if (best.frombit != 0 || best.tobit != 0)
{
int bix = 0;
while (bix < steps.numsteps && steps.steps[bix] != best)
{
bix++;
}
if (bix < steps.numsteps)
{
steps.steps[bix] = steps.steps[0];
steps.steps[0] = best;
num++;
step = &best;
stage++;
break;
}
debug (badhashstep)
{
parent.logger.log("step: f{} t{} p {}", ix_to_alg(best.fromix),
ix_to_alg(best.toix), best.push);
parent.logger.log("pos: {}{} {}", "gs"[pos.side],
pos.stepsLeft, pos.to_short_str());
}
if (best.push)
{
bix = 0;
while (bix < steps.numsteps
&& (steps.steps[bix].frombit != best.frombit
|| steps.steps[bix].tobit != best.tobit))
{
++bix;
}
if (bix < steps.numsteps)
{
parent.logger.warn("Hash step had push instead of pull.");
best.push = false;
steps.steps[bix] = steps.steps[0];
steps.steps[0] = best;
num++;
step = &best;
stage++;
break;
}
}
parent.logger.warn("Did not find hash step in step list");
}
stage++;
case 1:
if (capture_first && !pos.inpush)
{
if (!captures_generated)
{
parent.trap_search.find_captures(pos, pos.side);
if (capture_steps is null)
capture_steps = StepList.allocate();
else
capture_steps.clear();
for (int i=0; i < parent.trap_search.num_captures; i++)
{
if (parent.trap_search.captures[i].length <= pos.stepsLeft
&& parent.trap_search.captures[i].first_step != best)
{
Step* nstep = capture_steps.newstep();
*nstep = parent.trap_search.captures[i].first_step;
}
}
parent.trap_search.clear();
capture_num = 0;
captures_generated = true;
}
while (capture_num < capture_steps.numsteps)
{
Step* cstep = &capture_steps.steps[capture_num];
if (considered[cstep.fromix] & cstep.tobit)
{
capture_num++;
continue;
}
int bix = num;
while ((bix < steps.numsteps)
&& (steps.steps[bix] != *cstep))
{
bix++;
}
if (bix < steps.numsteps)
{
Step tmp = steps.steps[num];
steps.steps[num] = steps.steps[bix];
steps.steps[bix] = tmp;
step = &steps.steps[num++];
break;
} else {
bool had_pull = false; // had the move as a pull or already used in previous step
for (int i=num; i < steps.numsteps; i++)
{
if (cstep.frombit == steps.steps[i].frombit
&& (cstep.tobit == steps.steps[i].tobit))
{
had_pull = true;
break;
}
}
if (!had_pull)
{
debug (missing_captures)
{
writefln("%s\n%s", "wb"[pos.side], pos.to_long_str());
writefln("step %s, cnum %d, num %d, stepsleft %d lf %s%s",
cstep.toString(true),
capture_num-1, num, pos.stepsLeft,
"xRCDHMErcdhme"[pos.lastpiece], ix_to_alg(pos.lastfrom));
if (best.frombit != 0 || best.tobit != 0)
writefln("Have previous best");
else
writefln("No previous best");
writefln("Move steps:");
int sn = 0;
while (sn < steps.numsteps)
{
for (int i=0; i < 10; i++)
{
if (sn < steps.numsteps)
writef("%s ", steps.steps[sn++].toString(true));
else
break;
}
writef("\n");
}
writefln("Capture steps:");
sn = 0;
while (sn < capture_steps.numsteps)
{
for (int i=0; i < 10; i++)
{
if (sn < capture_steps.numsteps)
writef("%s ", capture_steps.steps[sn++].toString(true));
else
break;
}
writef("\n");
}
writefln("Did not find capture step in list");
assert (0);
}
parent.logger.warn("Did not find capture step in legal step list.");
}
capture_num++;
}
}
if (capture_num < capture_steps.numsteps)
{
capture_num++;
break;
} else {
StepList.free(capture_steps);
capture_steps = null;
}
}
stage++;
case 2:
if (use_killers && !pos.inpush && height < parent.killers.MAX_HEIGHT)
{
bool foundkiller = false;
while (sub_ix < 2)
{
Step* possible = &parent.killers.steps[height][pos.side][sub_ix++];
if (possible.frombit != 0 || possible.tobit != 0)
{
if (possible.frombit != INV_STEP
&& considered[possible.fromix] & possible.tobit)
continue;
if (remove_unrelated && !is_related(possible))
continue;
int bix = num;
while (bix < steps.numsteps && steps.steps[bix] != *possible)
{
bix++;
}
if (bix < steps.numsteps)
{
steps.steps[bix] = steps.steps[num];
steps.steps[num] = *possible;
num++;
step = possible;
if (sub_ix > 1)
{
stage++;
}
foundkiller = true;
break;
}
} else {
break;
}
}
if (foundkiller)
break;
}
stage++;
case 3:
if (remove_unrelated)
{
int s=num;
while (s < steps.numsteps)
{
Step* tstep = &steps.steps[s];
if ((tstep.frombit != INV_STEP
&& (considered[tstep.fromix] & tstep.tobit))
|| !is_related(tstep))
{
steps.numsteps--;
*tstep = steps.steps[steps.numsteps];
} else {
s++;
}
}
remove_unrelated = false;
if (num == steps.numsteps)
{
return null;
}
}
if (use_history)
{
uint score = parent.cuthistory.get_score(pos, steps.steps[num]);
int bix = num;
for (int i = num+1; i < steps.numsteps; i++)
{
int t = parent.cuthistory.get_score(pos, steps.steps[i]);
if (t > score)
{
score = t;
bix = i;
}
}
Step tmp = steps.steps[num];
steps.steps[num] = steps.steps[bix];
steps.steps[bix] = tmp;
step = &steps.steps[num++];
history_num++;
break;
}
stage++;
default:
step = &steps.steps[num++];
}
if (step.frombit != INV_STEP)
considered[step.fromix] |= step.tobit;
return step;
}
}
class ABSearch
{
Logger logger;
TransTable ttable;
HistoryHeuristic cuthistory;
KillerHeuristic killers;
TrapGenerator trap_search;
GoalSearchDT goal_search;
StepSorter[] sorters;
Position[] position_cache;
Position[] nullposition_cache;
Position nullmove;
int max_depth;
ulong nodes_searched;
ulong tthits;
ulong check_nodes;
uint check_interval = 100000;
bool delegate() should_abort;
bool use_lmr = true;
bool use_nmh = true;
bool use_early_beta = true;
this(Logger l, TransTable t)
{
logger = l;
ttable = t;
cuthistory = new HistoryHeuristic();
trap_search = new TrapGenerator();
goal_search = new GoalSearchDT();
killers = new KillerHeuristic();
nodes_searched = 0;
tthits = 0;
}
bool set_option(char[] option, char[] value)
{
bool handled = true;
switch (option)
{
case "history":
StepSorter.use_history = to!(bool)(value);
break;
case "capture_sort":
StepSorter.capture_first = to!(bool)(value);
break;
case "use_lmr":
use_lmr = to!(bool)(value);
break;
case "use_nmh":
use_nmh = to!(bool)(value);
break;
case "use_early_beta":
use_early_beta = to!(bool)(value);
break;
case "use_killers":
StepSorter.use_killers = to!(bool)(value);
break;
case "prune_unrelated":
StepSorter.prune_unrelated = to!(bool)(value);
break;
default:
handled = false;
break;
}
return handled;
}
int eval(Position pos, int alpha, int beta)
{
throw new Exception("eval must be implemented");
}
int static_eval(Position pos)
{
throw new Exception("eval must be implemented");
}
int logged_eval(Position pos)
{
throw new Exception("eval must be implemented");
}
int alphabeta(Position pos, int depth, int alpha, int beta, int height, Step* last_step = null)
{
nodes_searched++;
int score = MIN_SCORE;
if (pos.is_endstate() && (pos.stepsLeft == 4
|| !pos.is_goal(cast(Side)(pos.side^1))))
{
score = pos.endscore() * WIN_SCORE;
if (pos.side == Side.BLACK)
{
score = -score;
}
return score;
}
SType sflag = SType.ALPHA;
TTNode* node = ttable.get(pos);
Step* prev_best;
if (node.zobrist == pos.zobrist)
{
node.aged = false;
if (node.depth >= depth)
{
if (node.type == SType.EXACT
|| (node.type == SType.ALPHA && node.score <= alpha)
|| (node.type == SType.BETA && node.score >= beta))
{
tthits++;
return node.score;
}
}
prev_best = &node.beststep;
}
bool in_pv = (alpha+1) != beta;
Step new_best;
bool stop_search = false;
if (!pos.inpush && depth < 1)
{
if (in_pv && height <= max_depth + 8)
{
goal_search.set_start(pos);
goal_search.find_goals();
if (goal_search.shortest[pos.side^1] == goal_search.NOT_FOUND
|| goal_search.shortest[pos.side] <= pos.stepsLeft)
stop_search = true;
} else {
stop_search = true;
}
}
if (stop_search)
{
score = eval(pos, alpha, beta);
if (score == ABORT_SCORE
|| score == -ABORT_SCORE)
return ABORT_SCORE;
if (score > alpha)
{
alpha = score;
sflag = SType.EXACT;
if (score >= beta)
{
sflag = SType.BETA;
}
}
new_best.clear();
} else {
if (use_nmh && depth > 4 && !pos.inpush && pos.stepsLeft < 4)
{
Position mynull = nullmove;
nullmove = pos;
Position n = pos.dup;
n.do_step(NULL_STEP);
use_nmh = false;
int null_score = -alphabeta(n, depth-4, -beta, -alpha, height+1);
use_nmh = true;
Position.free(n);
nullmove = mynull;
if (score == -ABORT_SCORE
|| score == ABORT_SCORE)
return ABORT_SCORE;
if (null_score >= beta)
return null_score;
}
if (use_early_beta && depth < pos.stepsLeft)
{
int short_score = eval(pos, alpha, beta);
if (short_score >= beta)
return short_score;
}
StepSorter sorted_steps;
if (sorters.length > height)
{
sorted_steps = sorters[height];
sorted_steps.init(this, height, pos, prev_best, last_step);
} else {
sorted_steps = StepSorter.allocate(this, height, pos, prev_best, last_step);
sorters.length = height+1;
sorters[height] = sorted_steps;
}
if (depth > max_depth - 4 && depth > max_depth / 2)
sorted_steps.remove_unrelated = false;
Step* curstep = sorted_steps.next_step();
if (curstep is null)
{
// immobilized
return -WIN_SCORE;
}
Position npos;
if (position_cache.length > height)
{
npos = position_cache[height];
} else {
npos = Position.allocate();
position_cache.length = height+1;
position_cache[height] = npos;
}
Position nullreplace;
if (nullposition_cache.length > height)
{
nullreplace = nullposition_cache[height];
} else {
nullreplace = Position.allocate();
nullposition_cache.length = height+1;
nullposition_cache[height] = nullreplace;
}
while (curstep !is null)
{
int cal;
npos.copy(pos);
npos.do_step(*curstep);
if (npos == nullmove)
{
cal = -(WIN_SCORE+1); // Make this worse than a normal
// loss since it's actually an illegal move
} else {
bool had_nw = false;
int first_val;
if (use_lmr && !in_pv && depth > 2
&& sorted_steps.num > 3
&& sorted_steps.history_num > 1)
{
use_lmr = false;
if (npos.stepsLeft == 4)
{
Position mynull = nullmove;
nullreplace.copy(npos);
nullmove = nullreplace;
nullmove.do_step(NULL_STEP);
first_val = -alphabeta(npos, depth-2, -(alpha+1), -alpha, height+1, curstep);
nullmove = mynull;
} else {
first_val = alphabeta(npos, depth-2, alpha, alpha+1, height+1, curstep);
}
had_nw = true;
use_lmr = true;
}
else if (in_pv && sorted_steps.num > 1) // NegaScout
{
if (npos.stepsLeft == 4)
{
Position mynull = nullmove;
nullreplace.copy(npos);
nullmove = nullreplace;
nullmove.do_step(NULL_STEP);
first_val = -alphabeta(npos, depth-1, -(alpha+1), -alpha, height+1, curstep);
nullmove = mynull;
} else {
first_val = alphabeta(npos, depth-1, alpha, alpha+1, height+1, curstep);
}
had_nw = true;
}
if (first_val == ABORT_SCORE || first_val == -ABORT_SCORE)
{
score = ABORT_SCORE;
break;
}
if (!had_nw)
{
if (npos.stepsLeft == 4)
{
Position mynull = nullmove;
nullreplace.copy(npos);
nullmove = nullreplace;
nullmove.do_step(NULL_STEP);
cal = -alphabeta(npos, depth-1, -beta, -alpha, height+1, curstep);
nullmove = mynull;
} else {
cal = alphabeta(npos, depth-1, alpha, beta, height+1, curstep);
}
}
else if (first_val > alpha)
{
if (npos.stepsLeft == 4)
{
Position mynull = nullmove;
nullreplace.copy(npos);
nullmove = nullreplace;
nullmove.do_step(NULL_STEP);
cal = -alphabeta(npos, depth-1, -beta, -(first_val-1), height+1, curstep);
nullmove = mynull;
} else {
cal = alphabeta(npos, depth-1, first_val-1, beta, height+1, curstep);
}
} else {
cal = first_val;
}
}
if (cal == ABORT_SCORE
|| cal == -ABORT_SCORE)
{
score = ABORT_SCORE;
break;
}
if (cal > score)
{
score = cal;
new_best = *curstep;
if (cal > alpha)
{
alpha = cal;
sflag = SType.EXACT;
if (cal >= beta)
{
sflag = SType.BETA;
break;
}
}
}
curstep = sorted_steps.next_step();
}
if (sflag != SType.ALPHA && !pos.inpush)
{
cuthistory.update(pos, new_best, depth);
killers.set_killer(height, pos.side, new_best);
}
if (score == ABORT_SCORE)
return ABORT_SCORE;
}
node.set(pos, depth, score, sflag, new_best);
if (nodes_searched > check_nodes)
{
if (should_abort())
{
return ABORT_SCORE;
}