diff --git a/jagua-rs/src/entities/problems/bin_packing.rs b/jagua-rs/src/entities/problems/bin_packing.rs
index fa2b590..806707c 100644
--- a/jagua-rs/src/entities/problems/bin_packing.rs
+++ b/jagua-rs/src/entities/problems/bin_packing.rs
@@ -16,7 +16,7 @@ use crate::util::assertions;
 #[derive(Clone)]
 pub struct BPProblem {
     pub instance: BPInstance,
-    layouts: Vec<Layout>,
+    pub layouts: Vec<Layout>,
     template_layouts: Vec<Layout>,
     missing_item_qtys: Vec<isize>,
     bin_qtys: Vec<usize>,
@@ -154,7 +154,7 @@ impl ProblemGeneric for BPProblem {
 
     fn create_solution(&mut self, old_solution: &Option<Solution>) -> Solution {
         let id = self.next_solution_id();
-        let included_item_qtys = self.included_item_qtys();
+        let included_item_qtys = self.placed_item_qtys().collect_vec();
         let bin_qtys = self.bin_qtys().to_vec();
         let layout_snapshots = match old_solution {
             Some(old_solution) => {
@@ -269,15 +269,13 @@ impl ProblemGeneric for BPProblem {
         &self.missing_item_qtys
     }
 
-    fn included_item_qtys(&self) -> Vec<usize> {
-        (0..self.missing_item_qtys().len())
-            .map(|i| (self.instance.item_qty(i) as isize - self.missing_item_qtys()[i]) as usize)
-            .collect_vec()
-    }
-
     fn bin_qtys(&self) -> &[usize] {
         &self.bin_qtys
     }
+
+    fn instance(&self) -> &dyn InstanceGeneric {
+        &self.instance
+    }
 }
 
 
diff --git a/jagua-rs/src/entities/problems/problem.rs b/jagua-rs/src/entities/problems/problem.rs
index 4c96910..74b3f87 100644
--- a/jagua-rs/src/entities/problems/problem.rs
+++ b/jagua-rs/src/entities/problems/problem.rs
@@ -1,3 +1,4 @@
+use crate::entities::instances::instance_generic::InstanceGeneric;
 use crate::entities::layout::Layout;
 use crate::entities::placed_item::PlacedItemUID;
 use crate::entities::placing_option::PlacingOption;
@@ -79,17 +80,17 @@ impl ProblemGeneric for Problem {
         }
     }
 
-    fn included_item_qtys(&self) -> Vec<usize> {
+    fn bin_qtys(&self) -> &[usize] {
         match self {
-            Problem::BP(bp) => bp.included_item_qtys(),
-            Problem::SP(sp) => sp.included_item_qtys(),
+            Problem::BP(bp) => bp.bin_qtys(),
+            Problem::SP(sp) => sp.bin_qtys(),
         }
     }
 
-    fn bin_qtys(&self) -> &[usize] {
+    fn instance(&self) -> &dyn InstanceGeneric {
         match self {
-            Problem::BP(bp) => bp.bin_qtys(),
-            Problem::SP(sp) => sp.bin_qtys(),
+            Problem::BP(bp) => bp.instance(),
+            Problem::SP(sp) => sp.instance(),
         }
     }
 }
diff --git a/jagua-rs/src/entities/problems/problem_generic.rs b/jagua-rs/src/entities/problems/problem_generic.rs
index 6dbac5f..ca6dc45 100644
--- a/jagua-rs/src/entities/problems/problem_generic.rs
+++ b/jagua-rs/src/entities/problems/problem_generic.rs
@@ -1,4 +1,5 @@
 use std::borrow::Borrow;
+use crate::entities::instances::instance_generic::InstanceGeneric;
 
 use crate::entities::layout::Layout;
 use crate::entities::placed_item::PlacedItemUID;
@@ -31,10 +32,15 @@ pub trait ProblemGeneric: ProblemGenericPrivate {
     /// When an item is placed in a template layout, it is cloned into a real layout.
     fn template_layouts(&self) -> &[Layout];
 
-    /// The quantity of each item that is requested but currently missing in the problem instance.
-    /// Indexed by item id.
+    /// The quantity of each item that is requested but currently missing in the problem instance, indexed by item id.
     fn missing_item_qtys(&self) -> &[isize];
 
+    /// The quantity of each item that is currently placed in the problem instance, indexed by item id.
+    fn placed_item_qtys(&self) -> impl Iterator<Item=usize>{
+        self.missing_item_qtys().iter().enumerate()
+            .map(|(i, missing_qty)| (self.instance().item_qty(i) as isize - missing_qty) as usize)
+    }
+
     fn usage(&mut self) -> f64 {
         let (total_bin_area, total_used_area) = self.layouts_mut().iter_mut().fold((0.0, 0.0), |acc, l| {
             let bin_area = l.bin().area;
@@ -44,16 +50,16 @@ pub trait ProblemGeneric: ProblemGenericPrivate {
         total_used_area / total_bin_area
     }
 
-    fn used_bin_value(&self) -> u64 {
+    fn used_bin_cost(&self) -> u64 {
         self.layouts().iter().map(|l| l.bin().value).sum()
     }
 
-    fn included_item_qtys(&self) -> Vec<usize>;
-
+    /// Returns the `LayoutIndex` of all layouts.
     fn layout_indices(&self) -> impl Iterator<Item=LayoutIndex> {
         (0..self.layouts().len()).into_iter().map(|i| LayoutIndex::Real(i))
     }
 
+    /// Returns the `LayoutIndex` of all template layouts that have remaining stock.
     fn template_layout_indices_with_stock(&self) -> impl Iterator<Item=LayoutIndex> {
         self.template_layouts().iter().enumerate().filter_map(|(i, l)| {
             match self.bin_qtys()[l.bin().id] {
@@ -70,22 +76,13 @@ pub trait ProblemGeneric: ProblemGenericPrivate {
         }
     }
 
-    fn min_usage_layout_index(&mut self) -> Option<usize> {
-        (0..self.layouts().len())
-            .into_iter()
-            .min_by(|&i, &j|
-                self.layouts_mut()[i].usage()
-                    .partial_cmp(
-                        &self.layouts_mut()[j].usage()
-                    ).unwrap()
-            )
-    }
-
     fn bin_qtys(&self) -> &[usize];
 
     fn flush_changes(&mut self) {
         self.layouts_mut().iter_mut().for_each(|l| l.flush_changes());
     }
+
+    fn instance(&self) -> &dyn InstanceGeneric;
 }
 
 pub(super) mod private {
diff --git a/jagua-rs/src/entities/problems/strip_packing.rs b/jagua-rs/src/entities/problems/strip_packing.rs
index 350581b..6474ae4 100644
--- a/jagua-rs/src/entities/problems/strip_packing.rs
+++ b/jagua-rs/src/entities/problems/strip_packing.rs
@@ -22,7 +22,7 @@ use crate::util::config::CDEConfig;
 #[derive(Clone)]
 pub struct SPProblem {
     pub instance: SPInstance,
-    layout: Layout,
+    pub layout: Layout,
     strip_height: f64,
     strip_width: f64,
     missing_item_qtys: Vec<isize>,
@@ -116,7 +116,7 @@ impl ProblemGeneric for SPProblem {
 
     fn create_solution(&mut self, _old_solution: &Option<Solution>) -> Solution {
         let id = self.next_solution_id();
-        let included_item_qtys = self.included_item_qtys();
+        let included_item_qtys = self.placed_item_qtys().collect_vec();
         let bin_qtys = self.bin_qtys().to_vec();
         let layout_snapshots = vec![self.layout.create_layout_snapshot()];
         let target_item_qtys = self.instance.items.iter().map(|(_, qty)| *qty).collect_vec();
@@ -154,12 +154,6 @@ impl ProblemGeneric for SPProblem {
         &self.missing_item_qtys
     }
 
-    fn included_item_qtys(&self) -> Vec<usize> {
-        (0..self.missing_item_qtys().len())
-            .map(|i| (self.instance.item_qty(i) as isize - self.missing_item_qtys()[i]) as usize)
-            .collect_vec()
-    }
-
     fn template_layout_indices_with_stock(&self) -> impl Iterator<Item=LayoutIndex> {
         iter::empty::<LayoutIndex>()
     }
@@ -167,6 +161,10 @@ impl ProblemGeneric for SPProblem {
     fn bin_qtys(&self) -> &[usize] {
         &[0]
     }
+
+    fn instance(&self) -> &dyn InstanceGeneric {
+        &self.instance
+    }
 }
 
 
diff --git a/lbf/src/lbf_optimizer.rs b/lbf/src/lbf_optimizer.rs
index 8e93391..dbc0c0f 100644
--- a/lbf/src/lbf_optimizer.rs
+++ b/lbf/src/lbf_optimizer.rs
@@ -87,7 +87,7 @@ impl LBFOptimizer {
                     Some(i_opt) => {
                         info!("Placing item {} at {}", i_opt.item_id, i_opt.d_transf);
                         self.problem.place_item(&i_opt);
-                        if self.problem.included_item_qtys().iter().sum::<usize>() >= ITEM_LIMIT {
+                        if self.problem.placed_item_qtys().sum::<usize>() >= ITEM_LIMIT {
                             break 'outer;
                         }
                     }