Fix stochastic rounding and clipping

official-stockfish · Apr 7, 2024 · 7f0bfb0 · 7f0bfb0
1 parent 7f9ce2d
commit 7f0bfb0
Showing 1 changed file with 7 additions and 7 deletions.
diff --git a/server/fishtest/rundb.py b/server/fishtest/rundb.py
@@ -1505,8 +1505,8 @@ def purge_run(self, run, p=0.001, res=7.0, iters=1):
             self.buffer(run, True)
         return message
 
-    def spsa_param_clip(self, param, increment):
-        return min(max(param["theta"] + increment, param["min"]), param["max"])
+    def spsa_param_clip(self, param, increment, r):
+        return min(max(param["theta"] + increment + r, param["min"]), param["max"])
 
     # Store SPSA parameters for each worker
     spsa_params = {}
@@ -1556,15 +1556,15 @@ def generate_spsa(self, run):
             r = random.uniform(0, 1)
             flip = 1 if random.getrandbits(1) else -1
             # Stochastic rounding and probability for float N.p: (N, 1-p); (N+1, p)
-            w_value = math.floor(self.spsa_param_clip(param, c * flip) + r)
-            b_value = math.floor(self.spsa_param_clip(param, -c * flip) + r)
+            w_value = math.floor(self.spsa_param_clip(param, c * flip, r))
+            b_value = math.floor(self.spsa_param_clip(param, -c * flip, r))
             result["w_params"].append(
                 {
                     "name": param["name"],
                     "value": w_value,
                     "R": param["a"] / (spsa["A"] + iter_local) ** spsa["alpha"] / c**2,
-                    #Set c to the real delta after stochastic rounding is applied
-                    "c": abs(w_value - b_value),
+                    # Set c to the real delta after stochastic rounding is applied
+                    "c": abs(w_value - b_value) / 2,
                     "flip": flip,
                 }
             )
@@ -1600,7 +1600,7 @@ def update_spsa(self, worker, run, spsa_results):
             R = w_params[idx]["R"]
             c = w_params[idx]["c"]
             flip = w_params[idx]["flip"]
-            param["theta"] = self.spsa_param_clip(param, R * c * result * flip)
+            param["theta"] = self.spsa_param_clip(param, R * c * result * flip, 0)
             if grow_summary:
                 summary.append({"theta": param["theta"], "R": R, "c": c})