pulsatrix::ActivationSnapshot Class Reference

A copyable, self-contained record of every activation cached during one forward pass, plus the node ids in topological order and each node's op_type/label metadata. More...

#include <activation_snapshot.hpp>

Classes
struct	NodeMetadata
	Per-node metadata captured alongside the activation value. More...

Public Member Functions
	ActivationSnapshot (std::unordered_map< NodeId, Tensor > activations, std::vector< NodeId > node_ids, std::unordered_map< NodeId, NodeMetadata > metadata)
	Constructs a snapshot from already-captured data.
const Tensor &	activation (NodeId id) const
	The activation value captured at a node.
const std::vector< NodeId > &	node_ids () const
	Every captured node id, in topological order as of capture time.
OpType	op_type (NodeId id) const
	The op-type tag captured at a node.
std::optional< std::string >	label (NodeId id) const
	The optional label captured at a node.

Detailed Description

A copyable, self-contained record of every activation cached during one forward pass, plus the node ids in topological order and each node's op_type/label metadata.

Note

Holds no reference to the ComputationGraph or ExplainerContext it was captured from – deliberately. ExplainerContext::forward_pass() replaces its graph and activation cache wholesale on every call, and ComputationGraph is move-only (std::vector<std::unique_ptr<Node>>), so a snapshot that referred back to either would be invalidated by the very next forward pass. Copying the activation Tensors and the small amount of per-node metadata instead is what makes two snapshots from two different forward passes simultaneously alive and correct – the capability activation patching needs (campaign campaign_exai_dl_library_mechanistic_interpretability, Phase 4).

NodeIds are comparable across two snapshots taken from the same ExplainerContext: its module chain is fixed for its lifetime, so every forward pass builds a structurally identical graph (same node count, same op-type sequence, same ids), differing only in the cached values.

Constructed by ExplainerContext::activation_snapshot(), not assembled by hand.

Constructor & Destructor Documentation

ActivationSnapshot()

pulsatrix::ActivationSnapshot::ActivationSnapshot ( std::unordered_map< NodeId, Tensor >  activations, std::vector< NodeId >  node_ids, std::unordered_map< NodeId, NodeMetadata >  metadata  )

inline

Constructs a snapshot from already-captured data.

Parameters

activations	Deep copy of the cached activation value per node id.
node_ids	Node ids in topological order at capture time.
metadata	Per-node op_type/label, captured at the same moment.

Note

No cross-validation between the three arguments: this constructor is reached only from ExplainerContext::activation_snapshot(), which builds all three from one consistent graph in a single pass. An empty snapshot (all three empty) is a well-formed value, not an error – it is what a context that has not yet run a forward pass produces.

Member Function Documentation

activation()

const Tensor & pulsatrix::ActivationSnapshot::activation ( NodeId  id ) const

inline

The activation value captured at a node.

Parameters

id	Node id. Must be one of node_ids().

Note

Mirrors ExplainerContext::activation()'s not-found behavior (PULSATRIX_ASSERT): internal-only invariant per cpp_tdd/context_tdd_adversarial_boundary_testing.md's classification table – every id a caller can legitimately hold came from node_ids().

label()

std::optional< std::string > pulsatrix::ActivationSnapshot::label ( NodeId  id ) const

inline

The optional label captured at a node.

Parameters

id	Node id. Must be one of node_ids().

Returns

The node's label, or std::nullopt if it had none.

node_ids()

const std::vector< NodeId > & pulsatrix::ActivationSnapshot::node_ids ( ) const

inline

Every captured node id, in topological order as of capture time.

Note

The enumeration capability ExplainerContext's single-node activation() lookup lacks – Phase 2's linear probing iterates this to reach every cached layer.

op_type()

OpType pulsatrix::ActivationSnapshot::op_type ( NodeId  id ) const

inline

The op-type tag captured at a node.

Parameters

id	Node id. Must be one of node_ids().

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The documentation for this class was generated from the following file:

• include/pulsatrix/activation_snapshot.hpp