Extend policy impl

fancy_rl/policy.py

@@ -3,31 +3,63 @@ from tensordict.nn import TensorDictModule
 from torchrl.modules import MLP
 from tensordict.nn.distributions import NormalParamExtractor
 from fancy_rl.utils import is_discrete_space, get_space_shape
+from tensordict import TensorDict
 
 class Actor(TensorDictModule):
-    def __init__(self, obs_space, act_space, hidden_sizes, activation_fn, device):
+    def __init__(self, obs_space, act_space, hidden_sizes, activation_fn, device, full_covariance=False):
+        self.discrete = is_discrete_space(act_space)
         act_space_shape = get_space_shape(act_space)
-        if is_discrete_space(act_space):
+        
+        if self.discrete and full_covariance:
+            raise ValueError("Full covariance is not applicable for discrete action spaces.")
+        
+        self.full_covariance = full_covariance
+
+        if self.discrete:
             out_features = act_space_shape[-1]
+            out_keys = ["action_logits"]
+        else:
+            if full_covariance:
+                out_features = act_space_shape[-1] + (act_space_shape[-1] * (act_space_shape[-1] + 1)) // 2
+                out_keys = ["loc", "scale_tril"]
             else:
                 out_features = act_space_shape[-1] * 2
+                out_keys = ["loc", "scale"]
 
-        actor_module = nn.Sequential(
+        actor_module = MLP(
-            MLP(
             in_features=get_space_shape(obs_space)[-1],
             out_features=out_features,
             num_cells=hidden_sizes,
             activation_class=getattr(nn, activation_fn),
             device=device
-            ),
-            NormalParamExtractor() if not is_discrete_space(act_space) else nn.Identity(),
         ).to(device)
+
+        if not self.discrete:
+            if full_covariance:
+                param_extractor = FullCovarianceNormalParamExtractor(act_space_shape[-1])
+            else:
+                param_extractor = NormalParamExtractor()
+            actor_module = nn.Sequential(actor_module, param_extractor)
+
         super().__init__(
             module=actor_module,
             in_keys=["observation"],
-            out_keys=["loc", "scale"] if not is_discrete_space(act_space) else ["action_logits"],
+            out_keys=out_keys
         )
 
+class FullCovarianceNormalParamExtractor(nn.Module):
+    def __init__(self, action_dim):
+        super().__init__()
+        self.action_dim = action_dim
+
+    def forward(self, x):
+        loc = x[:, :self.action_dim]
+        scale_tril = torch.zeros(x.shape[0], self.action_dim, self.action_dim, device=x.device)
+        tril_indices = torch.tril_indices(row=self.action_dim, col=self.action_dim, offset=0)
+        scale_tril[:, tril_indices[0], tril_indices[1]] = x[:, self.action_dim:]
+        scale_tril.diagonal(dim1=-2, dim2=-1).exp_()
+        return TensorDict({"loc": loc, "scale_tril": scale_tril}, batch_size=x.shape[0])
+
 class Critic(TensorDictModule):
     def __init__(self, obs_space, hidden_sizes, activation_fn, device):
         critic_module = MLP(