diff --git a/core/src/model/order.rs b/core/src/model/order.rs
index 1394b9e592..ab8a236e55 100644
--- a/core/src/model/order.rs
+++ b/core/src/model/order.rs
@@ -17,7 +17,7 @@ where
 }
 
 /// Find a working evaluation order for a list of nodes.
-pub fn old_eval_order_for_nodes<F, O>(
+pub fn eval_order_for_nodes<F, O>(
     nodes: &[Node<F, O>],
     model_inputs: &[usize],
     model_outputs: &[usize],
@@ -82,7 +82,7 @@ where
 }
 
 /// Find a working evaluation order for a list of nodes.
-pub fn eval_order_for_nodes<F, O>(
+pub fn eval_order_for_nodes_memory<F, O>(
     nodes: &[Node<F, O>],
     _model_inputs: &[usize],
     model_outputs: &[usize],
@@ -93,16 +93,19 @@ where
     O: Debug + Display + AsRef<dyn Op> + AsMut<dyn Op> + Clone + 'static,
 {
     let mut ups = vec![tvec!(); nodes.len()];
+    let mut downs = vec![tvec!(); nodes.len()];
     for (ix, node) in nodes.iter().enumerate() {
         for input in &node.inputs {
             if !ups[ix].contains(&input.node) {
                 ups[ix].push(input.node);
+                downs[input.node].push(ix);
             }
         }
     }
     for (down, up) in more_dependencies {
-        if !ups[*down].contains(&up) {
+        if !ups[*down].contains(up) {
             ups[*down].push(*up);
+            downs[*up].push(*down);
         }
     }
     let costs: Vec<usize> = nodes
@@ -113,7 +116,13 @@ where
                 .map(|o| {
                     o.fact
                         .to_typed_fact()
-                        .map(|f| f.datum_type.size_of() * f.shape.volume().to_usize().unwrap_or(0))
+                        .map(|f| {
+                            f.datum_type.size_of()
+                                * f.shape
+                                    .as_concrete()
+                                    .map(|dims| dims.iter().product())
+                                    .unwrap_or(0)
+                        })
                         .unwrap_or(0)
                 })
                 .sum()
@@ -131,22 +140,33 @@ where
         }
     }
     let mut order = vec![];
+    let mut active = BitSet::with_capacity(nodes.len());
+    let mut candidates = BitSet::with_capacity(nodes.len());
+    candidates.extend(todo.iter().filter(|n| ups[*n].len() == 0));
     while todo.len() > 0 {
-        let next = todo
+        let next = candidates
             .iter()
             .filter(|n| !ups[*n].iter().any(|up| todo.contains(*up)))
             .min_by_key(|&candidate| {
-                todo.iter()
-                    .filter(|it| *it != candidate)
-                    .flat_map(|down| ups[down].iter().copied())
-                    .filter(|up| *up == candidate || !todo.contains(*up))
-                    .unique()
-                    .map(|n| costs[n])
-                    .sum::<usize>()
+                active.clear();
+                active.extend(
+                    todo.iter()
+                        .filter(|it| *it != candidate)
+                        .flat_map(|down| ups[down].iter().copied())
+                        .filter(|up| *up == candidate || !todo.contains(*up)),
+                );
+                active.iter().map(|n| costs[n]).sum::<usize>()
             })
             .context("Dependency loop detected.")?;
         order.push(next);
         todo.remove(next);
+        candidates.remove(next);
+        candidates.extend(
+            downs[next]
+                .iter()
+                .copied()
+                .filter(|n| todo.contains(*n) && ups[*n].iter().all(|up| !todo.contains(*up))),
+        );
     }
     Ok(order)
 }
diff --git a/core/src/plan.rs b/core/src/plan.rs
index 95a80ff800..00c048b1bd 100644
--- a/core/src/plan.rs
+++ b/core/src/plan.rs
@@ -3,11 +3,12 @@ use std::fmt::{Debug, Display};
 use std::marker::PhantomData;
 
 use crate::internal::*;
-use crate::model::order::eval_order_for_nodes;
 use crate::model::{Fact, Graph, OutletId};
 use crate::ops::konst::Const;
 use crate::ops::FrozenOpState;
 
+use self::order::eval_order_for_nodes_memory;
+
 #[derive(Default)]
 pub struct SessionState {
     pub inputs: HashMap<usize, TValue>,
@@ -78,7 +79,7 @@ where
         let inputs = model.borrow().input_outlets()?.iter().map(|n| n.node).collect::<Vec<usize>>();
         let outputs_nodes = outputs.iter().map(|n| n.node).collect::<Vec<usize>>();
         let mut order =
-            eval_order_for_nodes(model.borrow().nodes(), &inputs, &outputs_nodes, deps)?;
+            eval_order_for_nodes_memory(model.borrow().nodes(), &inputs, &outputs_nodes, deps)?;
         order.retain(|node| !model.borrow().node(*node).op_is::<Const>());
         let mut values_needed_until_step = vec![0; model.borrow().nodes().len()];
         for (step, node) in order.iter().enumerate() {