~25% speedup in selfplay due to: incremental zobrist hashing, smarter road checking, re-using the input computed for the NN

1 files changed, 2 insertions, 1 deletions

diff --git a/include/negamax.c b/include/negamax.c
index 6c29481..c86eeab 100644
--- a/include/negamax.c
+++ b/include/negamax.c
@@ -100,6 +100,7 @@ float negamax_generate(tak_state_p state) {
 
   // this is constant across iterative deepening
   const uint64_t root_hash = zobrist_compute(state);
+  state->hash = root_hash; // anchor the incremental hash at the root
 #ifdef RECORD_PV
   pv_leaf_t iteration_leaf;
 #endif
@@ -197,7 +198,7 @@ static float negamax(tak_state_p state, const uint8_t cur_depth,
 
     action_take(state, actions[idx]);
 
-    const uint64_t child_hash = zobrist_compute(state);
+    const uint64_t child_hash = state->hash;
 
     // Compute the value of the node and retain the leaf that produced it.
     float node_value;