Change default hyperparameters

scripts/impala.py

@@ -110,11 +110,11 @@ class Args:
     """whether to use the PPO clipping to replace V-Trace surrogate clipping"""
     clip_coef: float = 0.25
     """the PPO surrogate clipping coefficient"""
-    dual_clip_coef: Optional[float] = None
-    """the dual surrogate clipping coefficient"""
+    dual_clip_coef: Optional[float] = 3.0
+    """the dual surrogate clipping coefficient, typically 3.0"""
     ent_coef: float = 0.01
     """coefficient of the entropy"""
-    vf_coef: float = 0.5
+    vf_coef: float = 1.0
     """coefficient of the value function"""
     max_grad_norm: float = 1.0
     """the maximum norm for the gradient clipping"""

scripts/ppo.py

@@ -105,7 +105,7 @@ class Args:
     """Toggles advantages normalization"""
     clip_coef: float = 0.25
     """the surrogate clipping coefficient"""
-    dual_clip_coef: Optional[float] = None
+    dual_clip_coef: Optional[float] = 3.0
     """the dual surrogate clipping coefficient, typically 3.0"""
     spo_kld_max: Optional[float] = None
     """the maximum KLD for the SPO policy, typically 0.02"""