diff --git a/differential-dataflow/src/algorithms/graphs/propagate.rs b/differential-dataflow/src/algorithms/graphs/propagate.rs
index 3d5d8c65c..2728de6e2 100644
--- a/differential-dataflow/src/algorithms/graphs/propagate.rs
+++ b/differential-dataflow/src/algorithms/graphs/propagate.rs
@@ -77,7 +77,8 @@ where
     //               .reduce(|_, s, t| t.push((s[0].0.clone(), 1)))
     //      })
 
-    nodes.scope().iterative::<usize,_,_>(|scope| {
+    use timely::order::Product;
+    nodes.scope().scoped::<Product<_, usize>,_,_>("Propagate", |scope| {
 
         use crate::operators::iterate::Variable;
         use crate::trace::implementations::{ValBuilder, ValSpine};
diff --git a/differential-dataflow/src/algorithms/graphs/scc.rs b/differential-dataflow/src/algorithms/graphs/scc.rs
index f7bca525f..b730302e7 100644
--- a/differential-dataflow/src/algorithms/graphs/scc.rs
+++ b/differential-dataflow/src/algorithms/graphs/scc.rs
@@ -6,32 +6,11 @@ use std::hash::Hash;
 use timely::dataflow::*;
 
 use crate::{VecCollection, ExchangeData};
-use crate::operators::*;
 use crate::lattice::Lattice;
 use crate::difference::{Abelian, Multiply};
 
 use super::propagate::propagate;
 
-/// Iteratively removes nodes with no in-edges.
-pub fn trim<G, N, R>(graph: VecCollection<G, (N,N), R>) -> VecCollection<G, (N,N), R>
-where
-    G: Scope<Timestamp: Lattice+Ord>,
-    N: ExchangeData + Hash,
-    R: ExchangeData + Abelian,
-    R: Multiply<R, Output=R>,
-    R: From<i8>,
-{
-    graph.clone().iterate(|scope, edges| {
-        // keep edges from active edge destinations.
-        let graph = graph.enter(&scope);
-        let active =
-        edges.map(|(_src,dst)| dst)
-             .threshold(|_,c| if c.is_zero() { R::from(0_i8) } else { R::from(1_i8) });
-
-        graph.semijoin(active)
-    })
-}
-
 /// Returns the subset of edges in the same strongly connected component.
 pub fn strongly_connected<G, N, R>(graph: VecCollection<G, (N,N), R>) -> VecCollection<G, (N,N), R>
 where
@@ -41,10 +20,18 @@ where
     R: Multiply<R, Output=R>,
     R: From<i8>
 {
-    graph.clone().iterate(|scope, inner| {
+    use timely::order::Product;
+    graph.scope().scoped::<Product<_, usize>,_,_>("StronglyConnected", |scope| {
+        // Bring in edges and transposed edges.
         let edges = graph.enter(&scope);
         let trans = edges.clone().map_in_place(|x| mem::swap(&mut x.0, &mut x.1));
-        trim_edges(trim_edges(inner, edges), trans)
+        // Create a new variable that will be intra-scc edges.
+        use crate::operators::iterate::Variable;
+        let (variable, inner) = Variable::new_from(edges.clone(), Product::new(Default::default(), 1));
+
+        let result = trim_edges(trim_edges(inner, edges), trans);
+        variable.set(result.clone());
+        result.leave()
     })
 }
 
@@ -57,16 +44,24 @@ where
     R: Multiply<R, Output=R>,
     R: From<i8>
 {
-    let nodes = edges.clone()
-                     .map_in_place(|x| x.0 = x.1.clone())
-                     .consolidate();
+    edges.inner.scope().region_named("TrimEdges", |region| {
+        let cycle = cycle.enter_region(region);
+        let edges = edges.enter_region(region);
+
+        let nodes = edges.clone()
+                         .map_in_place(|x| x.0 = x.1.clone())
+                         .consolidate();
 
-    // NOTE: With a node -> int function, can be improved by:
-    // let labels = propagate_at(&cycle, &nodes, |x| *x as u64);
-    let labels = propagate(cycle, nodes);
+        // NOTE: With a node -> int function, can be improved by:
+        // let labels = propagate_at(&cycle, &nodes, |x| *x as u64);
+        let labels = propagate(cycle, nodes).arrange_by_key();
 
-    edges.join_map(labels.clone(), |e1,e2,l1| (e2.clone(),(e1.clone(),l1.clone())))
-         .join_map(labels, |e2,(e1,l1),l2| ((e1.clone(),e2.clone()),(l1.clone(),l2.clone())))
-         .filter(|(_,(l1,l2))| l1 == l2)
-         .map(|((x1,x2),_)| (x2,x1))
+        edges.arrange_by_key()
+             .join_core(labels.clone(), |e1,e2,l1| [(e2.clone(),(e1.clone(),l1.clone()))])
+             .arrange_by_key()
+             .join_core(labels, |e2,(e1,l1),l2| [((e1.clone(),e2.clone()),(l1.clone(),l2.clone()))])
+             .filter(|(_,(l1,l2))| l1 == l2)
+             .map(|((x1,x2),_)| (x2,x1))
+             .leave_region()
+    })
 }