Struct GraphTransaction 

pub struct GraphTransaction<'a, T> { /* private fields */ }

Tracks reversible changes to a Graph<T> and provides commit/rollback.

Usage:

• Mutate via push(...), attach(...), detach(...), change_direction(...).
• Call commit(), commit_with(...), or try_commit() to finalize.
• On invalid commit, the graph is rolled back and you receive replay steps you can pass to replay(...) in a fresh transaction.

Implementations

impl<'a, T> GraphTransaction<'a, T>

pub fn new(graph: &'a mut Graph<T>) -> Self

pub fn commit(self) -> TransactionResult<T>

Finalize the transaction:

• Marks cycles (set_cycles()).
• Validates with Graph<T>: Valid.
• If valid, returns Valid(steps).
• If invalid, rolls back and returns Invalid(steps, replay).

pub fn commit_with( self, validator: impl Fn(&Graph<T>) -> bool, ) -> TransactionResult<T>

Like commit(), but also requires validator(&Graph<T>) to pass.

This is useful for domain-specific acceptance checks in addition to structural validity.

pub fn try_commit(self) -> TransactionResult<T>

Attempt to commit the transaction, repairing invalid nodes if possible.

• Calls repair_invalid_nodes() up to MAX_REPAIR_ATTEMPTS times.

Note: This may produce different graphs on each call due to possible random repairs.

pub fn push(&mut self, node: impl Into<GraphNode<T>>) -> usize

Append a node to the graph and record the change. Returns the new node’s index.

pub fn attach(&mut self, from: usize, to: usize)

Create an edge from from to to and record the change.

pub fn detach(&mut self, from: usize, to: usize)

Remove an edge from from to to and record the change.

pub fn change_direction(&mut self, index: usize, direction: Direction)

Change the direction of the node at index if it differs from its current direction.

Records the previous direction so the change can be rolled back or replayed.

pub fn rollback(self) -> Vec<ReplayStep<T>>

Undo all recorded changes in reverse order, mutating the graph back to its original state.

Returns a sequence of ReplaySteps that can be fed to replay(...) on a new transaction to re-apply the same operational effects.

pub fn replay(&mut self, steps: Vec<ReplayStep<T>>)

Apply ReplaySteps (typically from a prior rollback()) to this transaction/graph.

Steps are recorded as normal mutations (so they can be committed or rolled back again).

pub fn set_cycles(&mut self)

Mark cycle participation for nodes touched in this transaction:

• Nodes without cycles are set to Direction::Forward.
• Nodes in cycles (via get_cycles(idx)) are set to Direction::Backward.

pub fn set_innovation( &mut self, node_idx: usize, innovation: Option<InnovationId>, )

pub fn get_insertion_steps( &self, source_idx: usize, target_idx: usize, new_node_idx: usize, rand: &mut RdRand<'_>, ) -> Vec<InsertStep>

Compute the steps needed to insert new_node_idx between source_idx and target_idx.

Behavior:

• If new_node has Arity::Zero and target is not locked, connect new_node -> target.
• If source is an Edge, re-route its single outgoing through new_node.
• If target is an Edge or is locked, detach one incoming and rewire via new_node.
• Otherwise connect source -> new_node -> target.

pub fn random_source_node(&self, rand: &mut RdRand<'_>) -> Option<&GraphNode<T>>

The below functions are used to get random nodes from the graph. These are useful for creating connections between nodes. Neither of these functions will return an edge node. This is because edge nodes are not valid source or target nodes for connections as they only allow one incoming and one outgoing connection, thus they can’t be used to create new connections. Instead, edge nodes are used to represent the weights of the connections

Get a random node that can be used as a source node for a connection. A source node can be either an input or a vertex node.

pub fn random_target_node(&self, rand: &mut RdRand<'_>) -> Option<&GraphNode<T>>

Get a random node that can be used as a target node for a connection. A target node can be either an output or a vertex node.

pub fn unique_random_source_node( &self, arity: &Arity, rand: &mut RdRand<'_>, ) -> Option<Vec<&GraphNode<T>>>

pub fn random_target_node_where<F>( &self, rand: &mut RdRand<'_>, filter: F, ) -> Option<&GraphNode<T>>

where F: Fn(&GraphNode<T>) -> bool,

Get a random target node that satisfies the provided filter function. This is essentially a filtered version of the above function random_target_node.

Methods from Deref<Target = Graph<T>>

pub fn len(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn get(&self, index: usize) -> Option<&GraphNode<T>>

pub fn iter(&self) -> impl Iterator<Item = &GraphNode<T>>

pub fn inputs(&self) -> impl Iterator<Item = &GraphNode<T>>

pub fn outputs(&self) -> impl Iterator<Item = &GraphNode<T>>

pub fn vertices(&self) -> impl Iterator<Item = &GraphNode<T>>

pub fn edges(&self) -> impl Iterator<Item = &GraphNode<T>>

pub fn get_cycles(&self, from: usize) -> HashSet<usize>

Get the cycles in the graph that include the node at the specified index.

Arguments

• index: The index of the node to get the cycles for.

Trait Implementations

impl<T> Deref for GraphTransaction<'_, T>

type Target = Graph<T>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.