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

1 files changed, 11 insertions, 10 deletions

diff --git a/include/zobrist.c b/include/zobrist.c
index 2922abf..5076fe1 100644
--- a/include/zobrist.c
+++ b/include/zobrist.c
@@ -50,18 +50,19 @@ void zobrist_free(void) {
 }
 
 
-// a position's value is from the perspective of the player to move, which flips
-// with parity, so we must track this
-#define PLY_PARITY_MAGIC 0x9E3779B97F4A7C15ULL
+uint64_t zobrist_cell(tak_state_p state, const uint8_t l) {
+  colour_stack_t c = state->colours[l];
+  const uint8_t count = COUNT_AT(state, l);
+  enum STONE_VARIANT s = STONE_AT(state, l);
+  uint64_t h = 0;
+  for (uint8_t hh = 0; hh < count; hh++, c >>= 1)
+    h ^= zobrist[l * (15 * 2 * 3) + hh * 2 * 3 + (c & 1) * 3 + s];
+  return h;
+}
 
 uint64_t zobrist_compute(tak_state_p state) {
   uint64_t hash = 0;
-  for (uint8_t l = 0; l < state->board_size * state->board_size; l++) {
-    colour_stack_t c = state->colours[l];
-    const uint8_t count = COUNT_AT(state, l);
-    enum STONE_VARIANT s = STONE_AT(state, l);
-    for (uint8_t h = 0; h < count; h++, c >>= 1)
-      hash ^= zobrist[l * (15 * 2 * 3) + h * 2 * 3 + (c & 1) * 3 + s];
-  }
+  for (uint8_t l = 0; l < state->board_size * state->board_size; l++)
+    hash ^= zobrist_cell(state, l);
   return hash ^ ((state->ply & 1) ? PLY_PARITY_MAGIC : 0);
 }