Avoid redundant cloning in SCC context updates

[justinbay]

update compute_scc_recursive to refresh lowlink in-place via get_mut, remove the per-iteration clone of the wrapper node and node id

[reviewable-StarkWare]

This change is 

[orizi]

@orizi reviewed all commit messages.
Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion

---

crates/cairo-lang-utils/src/graph_algos/strongly_connected_components.rs line 102 at r1 (raw file):

        // Update current_node in ctx.known_nodes without re-cloning the wrapper node.
        let wrapper_node = ctx.known_nodes.get_mut(&current_node_id).unwrap();
        wrapper_node.lowlink = current_wrapper_node.lowlink;

Suggestion:

    let mut current_lowlink = ctx.next_index;
    let current_node_id = current_node.get_id();
    ctx.known_nodes.insert(current_node_id.clone(), SccAlgoNode {
        node: current_node.clone(),
        index: ctx.next_index,
        lowlink: current_lowlink,
        on_stack: true,
    });
    ctx.next_index += 1;
    ctx.stack.push(current_node_id.clone());

    for neighbor in current_node.get_neighbors() {
        let neighbor_id = neighbor.get_id();
        match ctx.known_nodes.get(&neighbor_id) {
            None => {
                // neighbor was not visited yet. Visit it and maybe apply its lowlink to root.
                compute_scc_recursive(ctx, &neighbor);
                // Now neighbor should be in known_nodes.
                current_lowlink = core::cmp::min(
                    current_lowlink,
                    ctx.known_nodes[&neighbor_id].lowlink,
                );
            }
            Some(neighbor_node) => {
                if ctx.known_nodes[&neighbor_id].on_stack {
                    // This is a back edge, meaning neighbor is in current_node's SCC.
                    current_wrapper_node.lowlink =
                        core::cmp::min(current_wrapper_node.lowlink, neighbor_node.index);
                } else {
                    // If neighbor is known but not on stack, it's in a concluded dropped SCC.
                    // Ignore it.
                    continue;
                }
            }
        };

        // Update current_node's lowlink in ctx.known_nodes without re-cloning the wrapper node.
        ctx.known_nodes[&current_node_id].lowlink = current_lowlink;

[orizi]

No response. Closing.