Struct ReductionGraph 

pub struct ReductionGraph { /* private fields */ }

Runtime graph of all registered reductions.

Uses variant-level nodes: each node is a unique (problem_name, variant) pair. All edges come from inventory::iter::<ReductionEntry> registrations.

The graph supports:

• Auto-discovery of reductions from inventory::iter::<ReductionEntry>
• Dijkstra with custom cost functions
• Path finding by problem type or by name

Implementations

impl ReductionGraph

pub fn new() -> Self

Create a new reduction graph with all registered reductions from inventory.

pub fn variant_to_map(variant: &[(&str, &str)]) -> BTreeMap<String, String>

Convert a variant slice to a BTreeMap. Normalizes empty “graph” values to “SimpleGraph” for consistency.

pub fn find_cheapest_path<C: PathCostFn>( &self, source: &str, source_variant: &BTreeMap<String, String>, target: &str, target_variant: &BTreeMap<String, String>, input_size: &ProblemSize, cost_fn: &C, ) -> Option<ReductionPath>

Find the cheapest path between two specific problem variants.

Uses Dijkstra’s algorithm on the variant-level graph from the exact source variant node to the exact target variant node.

pub fn find_all_paths( &self, source: &str, source_variant: &BTreeMap<String, String>, target: &str, target_variant: &BTreeMap<String, String>, ) -> Vec<ReductionPath>

Find all simple paths between two specific problem variants.

Uses all_simple_paths on the variant-level graph from the exact source variant node to the exact target variant node.

pub fn has_direct_reduction<S: Problem, T: Problem>(&self) -> bool

Check if a direct reduction exists from S to T.

pub fn has_direct_reduction_by_name(&self, src: &str, dst: &str) -> bool

Check if a direct reduction exists by name.

pub fn problem_types(&self) -> Vec<&'static str>

Get all registered problem type names (base names).

pub fn num_types(&self) -> usize

Get the number of registered problem types (unique base names).

pub fn num_reductions(&self) -> usize

Get the number of registered reductions (edges).

pub fn num_variant_nodes(&self) -> usize

Get the number of variant-level nodes.

pub fn path_overheads(&self, path: &ReductionPath) -> Vec<ReductionOverhead>

Get the per-edge overhead expressions along a reduction path.

Returns one ReductionOverhead per edge (i.e., path.steps.len() - 1 items).

Panics if any step in the path does not correspond to an edge in the graph.

pub fn compose_path_overhead(&self, path: &ReductionPath) -> ReductionOverhead

Compose overheads along a path symbolically.

Returns a single ReductionOverhead whose expressions map from the source problem’s size variables directly to the final target’s size variables.

pub fn variants_for(&self, name: &str) -> Vec<BTreeMap<String, String>>

Get all variant maps registered for a problem name.

Returns variants sorted deterministically: the “default” variant (SimpleGraph, i32, etc.) comes first, then remaining variants in lexicographic order.

pub fn variant_complexity( &self, name: &str, variant: &BTreeMap<String, String>, ) -> Option<&'static str>

Get the complexity expression for a specific variant.

pub fn outgoing_reductions(&self, name: &str) -> Vec<ReductionEdgeInfo>

Get all outgoing reductions from a problem (across all its variants).

pub fn size_field_names(&self, name: &str) -> Vec<&'static str>

Get the problem size field names for a problem type.

Derives size fields from the overhead expressions of reduction entries where this problem appears as source or target. When the problem is a source, its size fields are the input variables referenced in the overhead expressions. When it’s a target, its size fields are the output field names.

pub fn incoming_reductions(&self, name: &str) -> Vec<ReductionEdgeInfo>

Get all incoming reductions to a problem (across all its variants).

pub fn k_neighbors( &self, name: &str, variant: &BTreeMap<String, String>, max_hops: usize, direction: TraversalDirection, ) -> Vec<NeighborInfo>

Find all problems reachable within max_hops edges from a starting node.

Returns neighbors sorted by (hops, name). The starting node itself is excluded. If a node is reachable at multiple distances, it appears at the shortest distance only.

pub fn k_neighbor_tree( &self, name: &str, variant: &BTreeMap<String, String>, max_hops: usize, direction: TraversalDirection, ) -> Vec<NeighborTree>

Build a tree of neighbors via BFS with parent tracking.

Returns the children of the starting node as a forest of NeighborTree nodes. Each node appears at most once (shortest-path tree). Children are sorted by name.

impl ReductionGraph

pub fn to_json_string(&self) -> Result<String, Error>

Export the reduction graph as a JSON string.

pub fn to_json_file(&self, path: &Path) -> Result<()>

Export the reduction graph to a JSON file.

pub fn find_best_entry( &self, source_name: &str, target_name: &str, current_variant: &BTreeMap<String, String>, ) -> Option<MatchedEntry>

Find the best matching ReductionEntry for a (source_name, target_name) pair given the caller’s current source variant.

First tries an exact match on the source variant. If no exact match is found, falls back to a name-only match (returning the first entry whose source and target names match). This is intentional: specific variants (e.g., K3) may not have their own #[reduction] entry, but the general variant (KN) covers them with the same overhead expression. The fallback is safe because cross-name reductions share the same overhead regardless of source variant; it is only used by the JSON export pipeline (export::lookup_overhead).

impl ReductionGraph

pub fn reduce_along_path( &self, path: &ReductionPath, source: &dyn Any, ) -> Option<ReductionChain>

Execute a reduction path on a source problem instance.

Looks up each edge’s reduce_fn, chains them, and returns the resulting ReductionChain. The source must be passed as &dyn Any (use &problem as &dyn Any or pass a concrete reference directly).

Example

let chain = graph.reduce_along_path(&path, &source_problem)?;
let target: &QUBO<f64> = chain.target_problem();
let source_solution = chain.extract_solution(&target_solution);

Trait Implementations

impl Default for ReductionGraph

fn default() -> Self

Returns the “default value” for a type.