Add "clear_cache" command.

No lz- prefix as this command existed in GNU Go as well.

Pull request leela-zero#2344.

src/GTP.cpp

@@ -399,6 +399,7 @@ const std::string GTP::s_commands[] = {
     "fixed_handicap",
     "last_move",
     "move_history",
+    "clear_cache",
     "place_free_handicap",
     "set_free_handicap",
     "loadsgf",
@@ -918,6 +919,10 @@ void GTP::execute(GameState & game, const std::string& xinput) {
         }
         gtp_printf_raw("\n");
         return;
+    } else if (command.find("clear_cache") == 0) {
+        s_network->nncache_clear();
+        gtp_printf(id, "");
+        return;
     } else if (command.find("place_free_handicap") == 0) {
         std::istringstream cmdstream(command);
         std::string tmp;

src/NNCache.cpp

@@ -86,6 +86,11 @@ void NNCache::resize(int size) {
     }
 }
 
+void NNCache::clear() {
+    m_cache.clear();
+    m_order.clear();
+}
+
 void NNCache::set_size_from_playouts(int max_playouts) {
     // cache hits are generally from last several moves so setting cache
     // size based on playouts increases the hit rate while balancing memory

src/NNCache.h

@@ -74,6 +74,7 @@ class NNCache {
 
     // Resize NNCache
     void resize(int size);
+    void clear();
 
     // Try and find an existing entry.
     bool lookup(std::uint64_t hash, Netresult & result);

src/Network.cpp

@@ -1033,3 +1033,7 @@ size_t Network::get_estimated_cache_size() {
 void Network::nncache_resize(int max_count) {
     return m_nncache.resize(max_count);
 }
+
+void Network::nncache_clear() {
+    m_nncache.clear();
+}

src/Network.h

@@ -104,6 +104,7 @@ class Network {
     size_t get_estimated_size();
     size_t get_estimated_cache_size();
     void nncache_resize(int max_count);
+    void nncache_clear();
 
 private:
     std::pair<int, int> load_v1_network(std::istream& wtfile);