bisimilarity working?

src/rsprocess/bisimilarity.rs

@@ -0,0 +1,174 @@
+use std::collections::{BTreeSet, HashMap};
+
+use petgraph::visit::{EdgeIndexable, EdgeRef, IntoEdgeReferences, IntoEdges, IntoNodeReferences, NodeIndexable};
+
+
+
+
+
+
+#[allow(dead_code)]
+fn print_type_of<T>(_: &T) {
+    println!("type: {}", std::any::type_name::<T>());
+}
+
+
+
+
+
+
+struct GraphPartition<'a, G>
+where
+    G: EdgeIndexable + NodeIndexable + IntoEdgeReferences + IntoNodeReferences
+    + IntoEdges,
+    G::NodeId: std::cmp::Eq + std::hash::Hash,
+{
+    pub node_to_block: HashMap<(usize, G::NodeId), u32>,
+    pub block_to_node: HashMap<u32, Vec<(usize, G::NodeId)>>,
+    pub graphs: [&'a G; 2],
+    last_block: u32,
+    blocks: BTreeSet<u32>
+}
+
+impl<'a, G> GraphPartition<'a, G>
+where
+    G: EdgeIndexable + NodeIndexable + IntoEdgeReferences + IntoNodeReferences
+    + IntoEdges,
+    G::NodeId: std::cmp::Eq + std::hash::Hash,
+{
+    pub fn new(graph_a: &'a G, graph_b: &'a G) -> Self {
+	GraphPartition { node_to_block: HashMap::new(),
+			 block_to_node:  HashMap::new(),
+			 graphs: [graph_a, graph_b],
+			 last_block: 0,
+			 blocks: BTreeSet::new() }
+    }
+
+    #[inline(always)]
+    pub fn add_node_last_partition(&mut self, node: G::NodeId, graph: usize) {
+	self.node_to_block.insert((graph, node), self.last_block);
+	self.block_to_node
+	    .entry(self.last_block)
+	    .or_default()
+	    .push((graph, node));
+	self.blocks.insert(self.last_block);
+    }
+
+    pub fn iterate_blocks(&self) -> Vec<u32> {
+	self.blocks.iter().cloned().collect::<Vec<_>>()
+    }
+
+    pub fn bisimilar(&self) -> bool {
+	// if there is a block that has only elements from one graph then they are
+	// not bisimilar
+	for (_block, node_list) in self.block_to_node.iter() {
+	    let graph_id = node_list.first().unwrap().0;
+	    if node_list.iter().all(|el| el.0 == graph_id) {
+		return false;
+	    }
+	}
+	true
+    }
+
+    fn reachable_blocks(
+	&self,
+	label: &G::EdgeRef,
+	s: &(usize, G::NodeId)
+    ) -> Vec<(usize, G::NodeId)>
+    where <G as IntoEdgeReferences>::EdgeRef: PartialEq
+    {
+	let mut val = vec![];
+	for el in self.graphs[s.0].edges(s.1).filter(|x| x == label) {
+	    val.push((s.0, el.target()));
+	}
+	val
+    }
+
+    pub fn split(&mut self, block: u32, label: &G::EdgeRef) -> bool
+    where <G as IntoEdgeReferences>::EdgeRef: PartialEq
+    {
+	let Some(nodes) = self.block_to_node.get(&block)
+	else {
+	    return true
+	};
+	let mut nodes = nodes.iter();
+	let s = nodes.next().unwrap();
+
+	let mut b1 = vec![s];
+	let mut b2 = vec![];
+
+	let reachable_blocks_s = self.reachable_blocks(label, s);
+
+	'outer: for t in nodes {
+	    let reachable_blocks_t = self.reachable_blocks(label, t);
+	    for rbt in reachable_blocks_t {
+		if !reachable_blocks_s.contains(&rbt) {
+		    b2.push(*t);
+		    continue 'outer;
+		}
+	    }
+	    b1.push(t);
+	}
+
+	if b2.is_empty() {
+	    // all elements go to the same block with label label, so no change
+	    false
+	} else {
+	    // some elements need to be split into a different block
+	    self.last_block += 1;
+	    let new_block = self.last_block;
+	    self.blocks.insert(new_block);
+
+	    for b in b2 {
+		self.node_to_block.entry(b).and_modify(|e| *e = new_block);
+		self.block_to_node.entry(new_block).or_default().push(b);
+		self.block_to_node.entry(block).and_modify(|e| {
+		    let index = e.iter().position(|x| *x == b).unwrap();
+		    e.remove(index);
+		});
+	    }
+	    true
+	}
+    }
+}
+
+pub fn bisimilarity_kanellakis_smolka<'a, G>(
+    graph_a: &'a G,
+    graph_b: &'a G
+) -> bool
+where
+    G: EdgeIndexable + NodeIndexable + IntoEdgeReferences + IntoNodeReferences
+    + IntoEdges,
+    G::NodeId: std::cmp::Eq + std::hash::Hash,
+    G::EdgeRef: PartialEq
+{
+    let graphs = [graph_a, graph_b];
+
+    let mut partition: GraphPartition<G> = GraphPartition::new(graph_a, graph_b);
+    for (p, graph) in graphs.iter().enumerate() {
+	for node in graph.node_identifiers() {
+	    partition.add_node_last_partition(node, p);
+	}
+    }
+
+    let labels =
+	graph_a.edge_references()
+	.chain(graph_b.edge_references())
+	.collect::<Vec<_>>();
+
+    let mut changed = true;
+
+    while changed {
+	changed = false;
+
+	for block in partition.iterate_blocks() {
+	    for label in labels.iter() {
+		if partition.split(block, label) {
+		    changed = true;
+		}
+	    }
+	}
+    }
+
+    partition.bisimilar()
+}