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Add policy mix option to value-only mode. #2004

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Add policy mix option to value-only mode. #2004

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33 changes: 29 additions & 4 deletions src/engine.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
#include "mcts/stoppers/factory.h"
#include "utils/commandline.h"
#include "utils/configfile.h"
#include "utils/fastmath.h"
#include "utils/logging.h"

namespace lczero {
Expand Down Expand Up @@ -71,6 +72,9 @@ const OptionId kValueOnly{
"In value only mode all search parameters are ignored and the position is "
"evaluated by getting the valuation of every child position and choosing "
"the worst for the opponent."};
const OptionId kPolicyMix{
"policy-mix", "PolicyMix",
"Amount to mix policy into the value in value-only mode."};
const OptionId kClearTree{"", "ClearTree",
"Clear the tree before the next search."};

Expand Down Expand Up @@ -131,6 +135,7 @@ void EngineController::PopulateOptions(OptionsParser* options) {

options->Add<BoolOption>(kPreload) = false;
options->Add<BoolOption>(kValueOnly) = false;
options->Add<FloatOption>(kPolicyMix, -2.0f, 2.0f) = 0.0f;
options->Add<ButtonOption>(kClearTree);
options->HideOption(kClearTree);
}
Expand Down Expand Up @@ -281,6 +286,9 @@ void ValueOnlyGo(NodeTree* tree, Network* network, const OptionsDict& options,
tree->GetCurrentHead()->CreateEdges(legal_moves);
PositionHistory history = tree->GetPositionHistory();
std::vector<InputPlanes> planes;
int transform;
planes.emplace_back(EncodePositionForNN(
input_format, history, 8, FillEmptyHistory::FEN_ONLY, &transform));
for (auto edge : tree->GetCurrentHead()->Edges()) {
history.Append(edge.GetMove());
if (history.ComputeGameResult() == GameResult::UNDECIDED) {
Expand All @@ -293,21 +301,36 @@ void ValueOnlyGo(NodeTree* tree, Network* network, const OptionsDict& options,
std::vector<float> comp_q;
int batch_size = options.Get<int>(SearchParams::kMiniBatchSizeId);
if (batch_size == 0) batch_size = network->GetMiniBatchSize();

bool policy_done = false;
std::vector<float> pol;
float max_p = 0.0f;
for (size_t i = 0; i < planes.size(); i += batch_size) {
auto comp = network->NewComputation();
for (int j = 0; j < batch_size; j++) {
comp->AddInput(std::move(planes[i + j]));
if (i + j + 1 == planes.size()) break;
}
comp->ComputeBlocking();

for (int j = 0; j < batch_size; j++) comp_q.push_back(comp->GetQVal(j));
int start = 0;
if (!policy_done) {
for (auto edge : tree->GetCurrentHead()->Edges()) {
pol.push_back(comp->GetPVal(0, edge.GetMove().as_nn_index(transform)));
if (pol.back() > max_p) max_p = pol.back();
}
start = 1;
policy_done = true;
}
for (int j = start; j < batch_size; j++) comp_q.push_back(comp->GetQVal(j));
}
float sum=0.0f;
for (int i=0; i < pol.size(); i++) {
pol[i] = FastExp(pol[i]-max_p)/options.Get<float>(SearchParams::kPolicySoftmaxTempId);
sum += pol[i];
}

Move best;
int comp_idx = 0;
float max_q = std::numeric_limits<float>::lowest();
int polidx=0;
for (auto edge : tree->GetCurrentHead()->Edges()) {
history.Append(edge.GetMove());
auto result = history.ComputeGameResult();
Expand All @@ -324,11 +347,13 @@ void ValueOnlyGo(NodeTree* tree, Network* network, const OptionsDict& options,
// win.
q = 1;
}
q += (pol[polidx])/sum*options.Get<float>(kPolicyMix);
if (q >= max_q) {
max_q = q;
best = edge.GetMove(tree->GetPositionHistory().IsBlackToMove());
}
history.Pop();
polidx++;
}
std::vector<ThinkingInfo> infos;
ThinkingInfo thinking;
Expand Down