diff --git a/lp/lp-optimizer.js b/lp/lp-optimizer.js
index 6aa9e863..9fdd4c9b 100644
--- a/lp/lp-optimizer.js
+++ b/lp/lp-optimizer.js
@@ -376,6 +376,40 @@ function put_aligned_pgs(aligned_pgs, int_pgs, prev_int_pgs, keygen)
     }
 }
 
+// Convert multi-level osd_tree = { level: number, id?: string, size?: number, children?: osd_tree }[]
+// to a two-level osd_tree suitable for all_combinations()
+function flatten_tree(osd_tree, failure_domain_level, osd_level, domains = {}, i = { i: 1 })
+{
+    for (const node of osd_tree)
+    {
+        if (node.level < failure_domain_level)
+        {
+            flatten_tree(node.children||[], failure_domain_level, osd_level, domains, i);
+        }
+        else
+        {
+            domains['dom'+(i.i++)] = extract_osds([ node ], osd_level);
+        }
+    }
+    return domains;
+}
+
+function extract_osds(osd_tree, osd_level, osds = {})
+{
+    for (const node of osd_tree)
+    {
+        if (node.level >= osd_level)
+        {
+            osds[node.id] = node.size;
+        }
+        else
+        {
+            extract_osds(node.children||[], osd_level, osds);
+        }
+    }
+    return osds;
+}
+
 function all_combinations(osd_tree, count, ordered)
 {
     const hosts = Object.keys(osd_tree).sort();
@@ -485,6 +519,7 @@ module.exports = {
     pg_weights_space_efficiency,
     pg_list_space_efficiency,
     pg_per_osd_space_efficiency,
+    flatten_tree,
 
     lp_solve,
     make_single,
diff --git a/lp/test-optimize.js b/lp/test-optimize.js
index 4c8e9046..fce5049d 100644
--- a/lp/test-optimize.js
+++ b/lp/test-optimize.js
@@ -40,20 +40,55 @@ const osd_tree = {
     },*/
 };
 
+const crush_tree = [
+    { level: 1, children: [
+        { level: 2, children: [
+            { level: 3, id: 1, size: 3 },
+            { level: 3, id: 2, size: 2 },
+        ] },
+        { level: 2, children: [
+            { level: 3, id: 3, size: 4 },
+            { level: 3, id: 4, size: 4 },
+        ] },
+    ] },
+    { level: 1, children: [
+        { level: 2, children: [
+            { level: 3, id: 5, size: 4 },
+            { level: 3, id: 6, size: 1 },
+        ] },
+        { level: 2, children: [
+            { level: 3, id: 7, size: 3 },
+            { level: 3, id: 8, size: 5 },
+        ] },
+    ] },
+    { level: 1, children: [
+        { level: 2, children: [
+            { level: 3, id: 9, size: 5 },
+            { level: 3, id: 10, size: 2 },
+        ] },
+        { level: 2, children: [
+            { level: 3, id: 11, size: 3 },
+            { level: 3, id: 12, size: 3 },
+        ] },
+    ] },
+];
+
 async function run()
 {
     // Test: add 1 OSD of almost the same size. Ideal data movement could be 1/12 = 8.33%. Actual is ~13%
     // Space efficiency is ~99.5% in both cases.
-    let prev = await LPOptimizer.optimize_initial(osd_tree, 256);
-    LPOptimizer.print_change_stats(prev, false);
+    let res = await LPOptimizer.optimize_initial(osd_tree, 256);
+    LPOptimizer.print_change_stats(res, false);
     console.log('adding osd.8');
     osd_tree[500][8] = 3.58589;
-    let next = await LPOptimizer.optimize_change(prev.int_pgs, osd_tree);
-    LPOptimizer.print_change_stats(next, false);
+    res = await LPOptimizer.optimize_change(res.int_pgs, osd_tree);
+    LPOptimizer.print_change_stats(res, false);
     console.log('removing osd.8');
     delete osd_tree[500][8];
-    next = await LPOptimizer.optimize_change(next.int_pgs, osd_tree);
-    LPOptimizer.print_change_stats(next, false);
+    res = await LPOptimizer.optimize_change(res.int_pgs, osd_tree);
+    LPOptimizer.print_change_stats(res, false);
+    res = await LPOptimizer.optimize_initial(LPOptimizer.flatten_tree(crush_tree, 1, 3), 256);
+    LPOptimizer.print_change_stats(res, false);
 }
 
 run().catch(console.error);