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Fix issue official-stockfish#1268

If the search is quit before skill.pick_best is called,
skill.best_move might be MOVE_NONE.

Ensure skill.best is always assigned anyhow.

Also retire the tricky best_move() and let the underlying
semantic to be clear and explicit.

No functional change.
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vondele authored and mcostalba committed Oct 11, 2017
1 parent 43c186c commit 9d791386825ef9797e62706654df8af8d36b6268
Showing with 4 additions and 5 deletions.
  1. +4 −5 src/search.cpp
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@@ -87,10 +87,9 @@ namespace {
// Skill structure is used to implement strength limit
struct Skill {
Skill(int l) : level(l) {}
explicit Skill(int l) : level(l) {}
bool enabled() const { return level < 20; }
bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
Move best_move(size_t multiPV) { return best ? best : pick_best(multiPV); }
Move pick_best(size_t multiPV);
int level;
@@ -514,8 +513,8 @@ void Thread::search() {
// If skill level is enabled, swap best PV line with the sub-optimal one
if (skill.enabled())
std::swap(rootMoves[0], *std::find(rootMoves.begin(),
rootMoves.end(), skill.best_move(multiPV)));
std::swap(rootMoves[0], *std::find(rootMoves.begin(), rootMoves.end(),
skill.best ? skill.best : skill.pick_best(multiPV)));
}
@@ -1451,7 +1450,7 @@ namespace {
int push = ( weakness * int(topScore - rootMoves[i].score)
+ delta * (rng.rand<unsigned>() % weakness)) / 128;
if (rootMoves[i].score + push > maxScore)
if (rootMoves[i].score + push >= maxScore)
{
maxScore = rootMoves[i].score + push;
best = rootMoves[i].pv[0];

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