Update README

README.md

@@ -12,7 +12,7 @@ JAX bindings and native implementations of differentiable trust region projectio
 - Multiple projection types:
   - KL (Kullback-Leibler divergence)
   - Wasserstein (only diagonal covariance)
-  - Frobenius (wip, not tested)
+  - Frobenius (wip, problem with cov projections)
   - Identity (no projection)
 - Support for both diagonal and full covariance Gaussians (induced from cholesky decomposition)
 - Contextual and non-contextual standard deviations (non-contextual means all standard deviations in batch are expected to be the same)

itpal_jax/kl_projection.py

@@ -88,8 +88,18 @@ class KLProjection(BaseProjection):
 
     def get_trust_region_loss(self, policy_params: Dict[str, jnp.ndarray], 
                              proj_policy_params: Dict[str, jnp.ndarray]) -> jnp.ndarray:
-        mean, scale_or_tril = policy_params["loc"], policy_params["scale"]
-        proj_mean, proj_scale_or_tril = proj_policy_params["loc"], proj_policy_params["scale"]
+        """Compute trust region loss between original and projected parameters."""
+        # Get the right scale parameter based on full_cov
+        mean = policy_params["loc"]
+        proj_mean = proj_policy_params["loc"]
+        
+        if self.full_cov:
+            scale_or_tril = policy_params["scale_tril"]
+            proj_scale_or_tril = proj_policy_params["scale_tril"]
+        else:
+            scale_or_tril = policy_params["scale"]
+            proj_scale_or_tril = proj_policy_params["scale"]
+
         kl = sum(self._gaussian_kl((mean, scale_or_tril), (proj_mean, proj_scale_or_tril)))
         return jnp.mean(kl) * self.trust_region_coeff
 
@@ -151,14 +161,12 @@ class KLProjection(BaseProjection):
             old_cov = old_scale_or_tril ** 2
 
         mask = cov_part > self.cov_bound
-        proj_scale_or_tril = jnp.zeros_like(scale_or_tril)
-        proj_scale_or_tril = jnp.where(~mask, scale_or_tril, proj_scale_or_tril)
         
         if mask.any():
             if self.full_cov:
                 proj_cov = project_full_covariance(cov, scale_or_tril, old_scale_or_tril, self.cov_bound)
-                is_invalid = jnp.isnan(proj_cov.mean(axis=(-2, -1))) & mask
-                proj_scale_or_tril = jnp.where(is_invalid, old_scale_or_tril, proj_scale_or_tril)
+                is_invalid = jnp.isnan(proj_cov.mean(axis=(-2, -1)))
+                proj_scale_or_tril = jnp.where(is_invalid[..., None, None], old_scale_or_tril, scale_or_tril)
                 mask = mask & ~is_invalid
                 chol = jnp.linalg.cholesky(proj_cov)
                 proj_scale_or_tril = jnp.where(mask[..., None, None], chol, proj_scale_or_tril)
@@ -166,10 +174,12 @@ class KLProjection(BaseProjection):
                 proj_cov = project_diag_covariance(cov, old_cov, self.cov_bound)
                 is_invalid = (jnp.isnan(proj_cov.mean(axis=-1)) | 
                             jnp.isinf(proj_cov.mean(axis=-1)) | 
-                            (proj_cov.min(axis=-1) < 0)) & mask
-                proj_scale_or_tril = jnp.where(is_invalid, old_scale_or_tril, proj_scale_or_tril)
+                            (proj_cov.min(axis=-1) < 0))
+                proj_scale_or_tril = jnp.where(is_invalid[..., None], old_scale_or_tril, scale_or_tril)
                 mask = mask & ~is_invalid
-                proj_scale_or_tril = jnp.where(mask[..., None], jnp.sqrt(proj_cov), proj_scale_or_tril)
+                proj_scale_or_tril = jnp.where(mask[..., None], jnp.sqrt(proj_cov), scale_or_tril)
+        else:
+            proj_scale_or_tril = scale_or_tril
 
         return proj_scale_or_tril
 

tests/test_projections.py

@@ -151,6 +151,10 @@ def test_full_covariance_projection(ProjectionClass):
     eigvals = jnp.linalg.eigvalsh(cov)
     assert jnp.all(eigvals > 0)
     
+    # Check trust region loss computation works
+    tr_loss = proj.get_trust_region_loss(params, proj_params)
+    assert jnp.isfinite(tr_loss)
+    
     # Only check KL bounds for KL projection
     if ProjectionClass in [KLProjection]:
         kl = compute_gaussian_kl(proj_params, old_params, full_cov=True)