2 files changed, 23 insertions, 14 deletions
diff --git a/src/mlia/nn/rewrite/core/graph_edit/diff.py b/src/mlia/nn/rewrite/core/graph_edit/diff.py
index 198e47e..7fa2a72 100644
--- a/src/mlia/nn/rewrite/core/graph_edit/diff.py
+++ b/src/mlia/nn/rewrite/core/graph_edit/diff.py
@@ -31,6 +31,21 @@ def add_total(name: str, key: str, values: list, totals: dict) -> None:
         totals[name][key] += values
 
 
+def _handle_zeros_in_denominator(denominator: np.ndarray) -> np.ndarray:
+    """Handle zeros in the denominator in nrmse to avoid dividing by zero(s)."""
+    denominator[denominator == 0.0] = 1.0
+    return denominator
+
+
+def calc_nrmse(rmse: dict, dataset1_var: dict) -> dict:
+    """Divide rmse by target standard deviation."""
+    nrmse = {
+        k: v / _handle_zeros_in_denominator(np.sqrt(dataset1_var[k]))
+        for k, v in rmse.items()
+    }
+    return nrmse
+
+
 def diff_stats(
     file1: str | Path, file2: str | Path, per_tensor_and_channel: bool = False
 ) -> tuple:
@@ -80,14 +95,8 @@ def diff_stats(
     mse = per_tensor_mean("se")
     rmse = {k: np.sqrt(v) for k, v in mse.items()}
     dataset1_var = per_tensor_mean("dataset1_variance")
-    is_nonzero = {k: dataset1_var[k] > 0 for k in dataset1_var}
 
-    # Divide by target standard deviation to get the per-channel nrmse for each
-    # tensor where possible
-    nrmse = {
-        k: v[is_nonzero[k]] / np.sqrt(dataset1_var[k][is_nonzero[k]])
-        for k, v in rmse.items()
-    }
+    nrmse = calc_nrmse(rmse, dataset1_var)
 
     if per_tensor_and_channel:
         return mae, nrmse
diff --git a/src/mlia/nn/rewrite/core/graph_edit/join.py b/src/mlia/nn/rewrite/core/graph_edit/join.py
index 14a7347..2530ec8 100644
--- a/src/mlia/nn/rewrite/core/graph_edit/join.py
+++ b/src/mlia/nn/rewrite/core/graph_edit/join.py
@@ -22,8 +22,8 @@ def join_models(
     input_src: str | Path,
     input_dst: str | Path,
     output_file: str | Path,
-    subgraph_src: SubGraphT = 0,
-    subgraph_dst: SubGraphT = 0,
+    subgraph_src: int = 0,
+    subgraph_dst: int = 0,
 ) -> None:
     """Join two models and save the result into a given model file path."""
     src_model = load(input_src)
@@ -150,12 +150,12 @@ def join_subgraphs(
     dst_subgraph.outputs = list(set(src_subgraph.outputs).union(dst_subgraph.outputs))
 
 
-def append_relabel(src: list, dst: list, operator_map: dict | None = None) -> dict:
-    """Return a map over relabeled tensors in a subgraph."""
-    if not operator_map:
-        operator_map = {}
+def append_relabel(src: list, dst: list, operator_map: dict) -> None:
+    """Update the operator map over relabeled tensors in a subgraph."""
+    if operator_map is None:
+        raise ValueError("The input operator map cannot be None!")
+
     for i, x in enumerate(src):  # pylint: disable=invalid-name
         if i not in operator_map:
             operator_map[i] = len(dst)
             dst.append(x)
-    return operator_map