Bug fix for swap

src/nnsight/intervention.py

@@ -138,6 +138,7 @@ def value(self) -> Any:
 
 
 def check_swap(graph: Graph, activations: Any, batch_start: int, batch_size: int):
+    # If swap is populated due to a 'swp' intervention.
     if graph.swap is not None:
 
         def concat(values):
@@ -154,27 +155,31 @@ def concat(values):
                     for key in values[0].keys()
                 }
 
+        # As interventions are scoped only to their relevant batch, if we want to swap in values for this batch
+        # we need to concatenate the batches before and after the relevant batch with the new values.
+        # Getting batch data before.
         pre = util.apply(
             activations, lambda x: x.narrow(0, 0, batch_start), torch.Tensor
         )
         post_batch_start = batch_start + batch_size
+        # Getting batch data after.
         post = util.apply(
             activations,
             lambda x: x.narrow(0, post_batch_start, x.shape[0] - post_batch_start),
             torch.Tensor,
         )
 
-        def get_value(node: Node):
-            value = node.value
-
-            node.set_value(True)
-
-            return value
-
-        value = util.apply(graph.swap, get_value, Node)
+        # Second argument of 'swp' interventions is the new value.
+        # Convert all Nodes in the value to their value.
+        value = util.apply(graph.swap.args[1], lambda x: x.value, Node)
 
+        # Concatenate
         activations = concat([pre, value, post])
 
+        # Set value of 'swp' node so it destroys itself and listeners.
+        graph.swap.set_value(True)
+
+        # Un-set swap.
         graph.swap = None
 
     return activations

src/nnsight/tracing/Graph.py

@@ -30,7 +30,7 @@ class Graph:
         module_proxy (Proxy): Proxy for given root meta module.
         argument_node_names (Dict[str, List[str]]): Map of name of argument to name of nodes that depend on it.
         generation_idx (int): Current generation index.
-        swap (Any): Attribute to store swap values from 'swp' nodes.
+        swap (Node): Attribute to store swap values from 'swp' nodes.
     """
 
     @staticmethod
@@ -129,7 +129,7 @@ def __init__(
 
         self.generation_idx = 0
 
-        self.swap: Any = None
+        self.swap: Node = None
 
     def increment(self) -> None:
         """Increments the generation_idx by one. Should be called by a forward hook on the model being used for generation."""

src/nnsight/tracing/Node.py

@@ -194,7 +194,7 @@ def execute(self) -> None:
         if self.target == "null":
             return
         elif self.target == "swp":
-            self.graph.swap = self.args[1]
+            self.graph.swap = self
 
             return
 
@@ -230,7 +230,7 @@ def set_value(self, value: Any):
             if dependency.redundant():
                 dependency.destroy()
 
-        if self.value is not None and self.redundant():
+        if self.value is not inspect._empty and self.redundant():
             self.destroy()
 
     def destroy(self) -> None: