Add MaximumClique<SimpleGraph, One> variant with weight cast and reductions

Register the One (unit weight) variant for MaximumClique so reduction paths
from MIS/SimpleGraph/One no longer require unnecessary weight promotion to
i32 before reaching MaxClique. Consolidate complement_edges into graph_helpers
to eliminate 3 duplicate copies (DRY).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: GiggleLiu

src/models/graph/maximum_clique.rs

@@ -6,7 +6,7 @@
 use crate::registry::{FieldInfo, ProblemSchemaEntry, VariantDimension};
 use crate::topology::{Graph, SimpleGraph};
 use crate::traits::Problem;
-use crate::types::{Max, WeightElement};
+use crate::types::{Max, One, WeightElement};
 use num_traits::Zero;
 use serde::{Deserialize, Serialize};
 
@@ -17,7 +17,7 @@ inventory::submit! {
         aliases: &[],
         dimensions: &[
             VariantDimension::new("graph", "SimpleGraph", &["SimpleGraph"]),
-            VariantDimension::new("weight", "i32", &["i32"]),
+            VariantDimension::new("weight", "One", &["One", "i32"]),
         ],
         module_path: module_path!(),
         description: "Find maximum weight clique in a graph",
@@ -165,7 +165,8 @@ fn is_clique_config<G: Graph>(graph: &G, config: &[usize]) -> bool {
 }
 
 crate::declare_variants! {
-    default MaximumClique<SimpleGraph, i32> => "1.1996^num_vertices",
+    MaximumClique<SimpleGraph, i32> => "1.1996^num_vertices",
+    default MaximumClique<SimpleGraph, One> => "1.1996^num_vertices",
 }
 
 #[cfg(feature = "example-db")]

src/rules/graph_helpers.rs

@@ -1,6 +1,6 @@
 //! Shared helpers for graph-based reductions.
 
-use crate::topology::Graph;
+use crate::topology::{Graph, SimpleGraph};
 
 /// Extract a Hamiltonian cycle vertex ordering from edge-selection configs on complete graphs.
 ///
@@ -57,3 +57,17 @@ pub(crate) fn edges_to_cycle_order<G: Graph>(graph: &G, target_solution: &[usize
 
     order
 }
+
+/// Build the complement graph edges: edges between all non-adjacent vertex pairs.
+pub(crate) fn complement_edges(graph: &SimpleGraph) -> Vec<(usize, usize)> {
+    let n = graph.num_vertices();
+    let mut edges = Vec::new();
+    for u in 0..n {
+        for v in (u + 1)..n {
+            if !graph.has_edge(u, v) {
+                edges.push((u, v));
+            }
+        }
+    }
+    edges
+}

src/rules/kcoloring_partitionintocliques.rs

@@ -29,18 +29,7 @@ impl ReductionResult for ReductionKColoringToPartitionIntoCliques {
     }
 }
 
-fn complement_edges(graph: &SimpleGraph) -> Vec<(usize, usize)> {
-    let n = graph.num_vertices();
-    let mut edges = Vec::new();
-    for u in 0..n {
-        for v in (u + 1)..n {
-            if !graph.has_edge(u, v) {
-                edges.push((u, v));
-            }
-        }
-    }
-    edges
-}
+use super::graph_helpers::complement_edges;
 
 #[reduction(
     overhead = {

src/rules/maximumclique_casts.rs

@@ -0,0 +1,18 @@
+//! Variant cast reductions for MaximumClique.
+//!
+//! Weight-hierarchy cast converting MaximumClique between weight subtypes.
+
+use crate::impl_variant_reduction;
+use crate::models::graph::MaximumClique;
+use crate::topology::SimpleGraph;
+use crate::types::One;
+use crate::variant::CastToParent;
+
+// Weight-hierarchy cast (One → i32)
+impl_variant_reduction!(
+    MaximumClique,
+    <SimpleGraph, One> => <SimpleGraph, i32>,
+    fields: [num_vertices, num_edges],
+    |src| MaximumClique::new(
+        src.graph().clone(), src.weights().iter().map(|w| w.cast_to_parent()).collect())
+);

src/rules/maximumclique_maximumindependentset.rs

@@ -7,7 +7,7 @@ use crate::models::graph::{MaximumClique, MaximumIndependentSet};
 use crate::reduction;
 use crate::rules::traits::{ReduceTo, ReductionResult};
 use crate::topology::{Graph, SimpleGraph};
-use crate::types::WeightElement;
+use crate::types::{One, WeightElement};
 
 /// Result of reducing MaximumClique to MaximumIndependentSet.
 #[derive(Debug, Clone)]
@@ -33,18 +33,15 @@ where
     }
 }
 
-/// Build the complement graph: edges between all non-adjacent vertex pairs.
-fn complement_edges(graph: &SimpleGraph) -> Vec<(usize, usize)> {
-    let n = graph.num_vertices();
-    let mut edges = Vec::new();
-    for u in 0..n {
-        for v in (u + 1)..n {
-            if !graph.has_edge(u, v) {
-                edges.push((u, v));
-            }
-        }
-    }
-    edges
+fn reduce_clique_to_is<W: WeightElement + Clone + Default>(
+    src: &MaximumClique<SimpleGraph, W>,
+) -> ReductionCliqueToIS<W> {
+    let comp_edges = super::graph_helpers::complement_edges(src.graph());
+    let target = MaximumIndependentSet::new(
+        SimpleGraph::new(src.graph().num_vertices(), comp_edges),
+        src.weights().to_vec(),
+    );
+    ReductionCliqueToIS { target }
 }
 
 #[reduction(
@@ -57,12 +54,21 @@ impl ReduceTo<MaximumIndependentSet<SimpleGraph, i32>> for MaximumClique<SimpleG
     type Result = ReductionCliqueToIS<i32>;
 
     fn reduce_to(&self) -> Self::Result {
-        let comp_edges = complement_edges(self.graph());
-        let target = MaximumIndependentSet::new(
-            SimpleGraph::new(self.graph().num_vertices(), comp_edges),
-            self.weights().to_vec(),
-        );
-        ReductionCliqueToIS { target }
+        reduce_clique_to_is(self)
+    }
+}
+
+#[reduction(
+    overhead = {
+        num_vertices = "num_vertices",
+        num_edges = "num_vertices * (num_vertices - 1) / 2 - num_edges",
+    }
+)]
+impl ReduceTo<MaximumIndependentSet<SimpleGraph, One>> for MaximumClique<SimpleGraph, One> {
+    type Result = ReductionCliqueToIS<One>;
+
+    fn reduce_to(&self) -> Self::Result {
+        reduce_clique_to_is(self)
     }
 }
 

src/rules/maximumindependentset_maximumclique.rs

@@ -7,7 +7,7 @@ use crate::models::graph::{MaximumClique, MaximumIndependentSet};
 use crate::reduction;
 use crate::rules::traits::{ReduceTo, ReductionResult};
 use crate::topology::{Graph, SimpleGraph};
-use crate::types::WeightElement;
+use crate::types::{One, WeightElement};
 
 /// Result of reducing MaximumIndependentSet to MaximumClique.
 #[derive(Debug, Clone)]
@@ -33,6 +33,17 @@ where
     }
 }
 
+fn reduce_is_to_clique<W: WeightElement + Clone + Default>(
+    src: &MaximumIndependentSet<SimpleGraph, W>,
+) -> ReductionISToClique<W> {
+    let comp_edges = super::graph_helpers::complement_edges(src.graph());
+    let target = MaximumClique::new(
+        SimpleGraph::new(src.graph().num_vertices(), comp_edges),
+        src.weights().to_vec(),
+    );
+    ReductionISToClique { target }
+}
+
 #[reduction(
     overhead = {
         num_vertices = "num_vertices",
@@ -43,21 +54,21 @@ impl ReduceTo<MaximumClique<SimpleGraph, i32>> for MaximumIndependentSet<SimpleG
     type Result = ReductionISToClique<i32>;
 
     fn reduce_to(&self) -> Self::Result {
-        let n = self.graph().num_vertices();
-        // Build complement graph edges
-        let mut complement_edges = Vec::new();
-        for u in 0..n {
-            for v in (u + 1)..n {
-                if !self.graph().has_edge(u, v) {
-                    complement_edges.push((u, v));
-                }
-            }
-        }
-        let target = MaximumClique::new(
-            SimpleGraph::new(n, complement_edges),
-            self.weights().to_vec(),
-        );
-        ReductionISToClique { target }
+        reduce_is_to_clique(self)
+    }
+}
+
+#[reduction(
+    overhead = {
+        num_vertices = "num_vertices",
+        num_edges = "num_vertices * (num_vertices - 1) / 2 - num_edges",
+    }
+)]
+impl ReduceTo<MaximumClique<SimpleGraph, One>> for MaximumIndependentSet<SimpleGraph, One> {
+    type Result = ReductionISToClique<One>;
+
+    fn reduce_to(&self) -> Self::Result {
+        reduce_is_to_clique(self)
     }
 }
 

src/rules/mod.rs

@@ -71,6 +71,7 @@ pub(crate) mod ksatisfiability_timetabledesign;
 pub(crate) mod longestcommonsubsequence_maximumindependentset;
 pub(crate) mod maxcut_minimumcutintoboundedsets;
 pub(crate) mod maximum2satisfiability_maxcut;
+mod maximumclique_casts;
 pub(crate) mod maximumclique_maximumindependentset;
 mod maximumindependentset_casts;
 mod maximumindependentset_gridgraph;