diff --git a/csf/src/fp/gocmap/mod.rs b/csf/src/fp/gocmap/mod.rs
index 2f6b412..872b7b0 100644
--- a/csf/src/fp/gocmap/mod.rs
+++ b/csf/src/fp/gocmap/mod.rs
@@ -61,8 +61,8 @@ impl<C: Coding, GS: GroupSize, SS: SeedSize, S: BuildSeededHasher> GOCMap<C, GS,
             let index = conf.goconf.bits_per_group.bit_index_for_seed(hash, group_seed(group), group);
             if collision_solver.is_under_collision(index) { continue }
             collision_solver.add_value(index,
-                                              coding.rev_fragment_of(values[i], value_rev_indices[i]),
-                                              bits_per_fragment);
+                    coding.rev_fragment_of(values[i], value_rev_indices[i]),
+                        bits_per_fragment);
         }
     }
 
diff --git a/csf/src/fp/gomap/conf.rs b/csf/src/fp/gomap/conf.rs
index 8eaaf96..229cf66 100644
--- a/csf/src/fp/gomap/conf.rs
+++ b/csf/src/fp/gomap/conf.rs
@@ -15,7 +15,7 @@ pub struct GOMapConf<
     /// Configuration of family of (group-optimized) hash functions (default: [`GOConf::default`]).
     pub goconf: GOConf<GS, SS, S>,
     /// Choose the size of each level.
-    pub level_size_chooser: LSC,
+    pub level_sizer: LSC,
     /// Constructs collision solver that decides which collisions are positive, and which are negative.
     pub collision_solver: CSB,
 }
@@ -23,7 +23,7 @@ pub struct GOMapConf<
 impl Default for GOMapConf {
     fn default() -> Self { Self {
         goconf: Default::default(),
-        level_size_chooser: Default::default(),
+        level_sizer: Default::default(),
         collision_solver: Default::default(),
     } }
 }
@@ -32,7 +32,7 @@ impl<CSB: CollisionSolverBuilder> GOMapConf<OptimalLevelSize, CSB, TwoToPowerBit
     pub fn cs(collision_solver: CSB) -> Self {
         Self {
             goconf: Default::default(),
-            level_size_chooser: Default::default(),
+            level_sizer: Default::default(),
             collision_solver,
         }
     }
@@ -42,7 +42,7 @@ impl<GS: GroupSize, SS: SeedSize, S> GOMapConf<OptimalLevelSize, LoMemAcceptEqua
     pub fn groups(goconf: GOConf<GS, SS, S>) -> Self {
         Self {
             goconf,
-            level_size_chooser: Default::default(),
+            level_sizer: Default::default(),
             collision_solver: Default::default(),
         }
     }
@@ -52,7 +52,7 @@ impl<CSB: CollisionSolverBuilder, GS: GroupSize, SS: SeedSize, S> GOMapConf<Opti
     pub fn groups_cs(goconf: GOConf<GS, SS, S>, collision_solver: CSB) -> Self {
         Self {
             goconf,
-            level_size_chooser: Default::default(),
+            level_sizer: Default::default(),
             collision_solver,
         }
     }
@@ -68,7 +68,7 @@ impl<LSC> GOMapConf<LSC, LoMemAcceptEquals, TwoToPowerBitsStatic::<4>, TwoToPowe
     pub fn lsize(level_size_chooser: LSC) -> Self {
         Self {
             goconf: Default::default(),
-            level_size_chooser,
+            level_sizer: level_size_chooser,
             collision_solver: Default::default(),
         }
     }
@@ -78,7 +78,7 @@ impl<LSC, CSB: CollisionSolverBuilder> GOMapConf<LSC, CSB, TwoToPowerBitsStatic:
     pub fn lsize_cs(level_size_chooser: LSC, collision_solver: CSB) -> Self {
         Self {
             goconf: Default::default(),
-            level_size_chooser,
+            level_sizer: level_size_chooser,
             collision_solver,
         }
     }
@@ -86,12 +86,12 @@ impl<LSC, CSB: CollisionSolverBuilder> GOMapConf<LSC, CSB, TwoToPowerBitsStatic:
 
 impl<LSC, GS: GroupSize, SS: SeedSize, S> GOMapConf<LSC, LoMemAcceptEquals, GS, SS, S> {
     pub fn groups_lsize(goconf: GOConf<GS, SS, S>, level_size_chooser: LSC) -> Self {
-        Self { goconf, level_size_chooser, collision_solver: Default::default() }
+        Self { goconf, level_sizer: level_size_chooser, collision_solver: Default::default() }
     }
 }
 
 impl<LSC, CSB: CollisionSolverBuilder, GS: GroupSize, SS: SeedSize, S> GOMapConf<LSC, CSB, GS, SS, S> {
     pub fn groups_lsize_cs(goconf: GOConf<GS, SS, S>, level_size_chooser: LSC, collision_solver: CSB) -> Self {
-        Self { goconf, level_size_chooser, collision_solver }
+        Self { goconf, level_sizer: level_size_chooser, collision_solver }
     }
 }
diff --git a/csf/src/fp/gomap/mod.rs b/csf/src/fp/gomap/mod.rs
index ec42fc6..7dab922 100644
--- a/csf/src/fp/gomap/mod.rs
+++ b/csf/src/fp/gomap/mod.rs
@@ -8,6 +8,11 @@ use std::hash::Hash;
 mod conf;
 pub use conf::GOMapConf;
 
+use crate::fp::CollisionSolver;
+
+use super::kvset::KVSet;
+use super::{CollisionSolverBuilder, LevelSizer};
+
 /// Finger-printing based compressed static function (immutable map)
 /// that uses group optimization and maps hashable keys to unsigned integer values of given bit-size.
 /// 
@@ -82,4 +87,38 @@ impl<GS: GroupSize, SS: SeedSize, S: BuildSeededHasher> GOMap<GS, SS, S> {
         self.get_stats_or_panic(key, &mut ())
     }
 
+    
+
+    pub fn with_conf_stats<K, KV, LSC, CSB, BS>(kv: KV, conf: GOMapConf<LSC, CSB, GS, SS, S>, stats: &mut BS) -> Self
+        where K: Hash, KV: KVSet<K>, LSC: LevelSizer, CSB: CollisionSolverBuilder, BS: stats::BuildStatsCollector
+    {
+        let bits_per_value = kv.bits_per_value();
+        let level_sizes = Vec::<usize>::new();
+        let arrays = Vec::<Box<[u64]>>::new();
+        let values_lens = Vec::<usize>::new();
+        let values = Vec::<Box<[u64]>>::new();
+        let groups = Vec::<Box<[u64]>>::new();
+        let mut input_size = kv.kv_len();
+        let mut level_nr = 0;
+        while input_size != 0 {           
+            let (level_size_groups, level_size_segments) = conf.goconf.bits_per_group
+                .level_size_groups_segments(conf.level_sizer.size_segments(&kv) * 64);
+            stats.level(input_size, level_size_segments * 64);
+            
+            let mut collision_solver: <CSB as CollisionSolverBuilder>::CollisionSolver = conf.collision_solver.new(level_size_segments, bits_per_value);
+            kv.process_all_values(|key| conf.goconf.key_index(key, level_nr, level_size_groups as u64,
+                |_| 0), &mut collision_solver);
+            let collisions = collision_solver.to_collision_array();
+            let mut best_counts = vec![0u32; level_size_groups].into_boxed_slice();
+            kv.for_each_key(|key| {
+                let hash = conf.goconf.hash_builder.hash_one(key, level_nr);
+                let group = group_nr(hash, level_size_groups as u64);
+                let bit_nr = conf.goconf.bits_per_group.bit_index_for_seed(hash, 0, group);
+                if collisions.get_bit(bit_nr) { best_counts[group as usize] += 1; }
+            });
+            let mut best_seeds = conf.goconf.bits_per_seed.new_zeroed_seed_vec(level_size_groups);
+            
+        }
+        todo!()
+    }
 }
diff --git a/csf/src/fp/kvset.rs b/csf/src/fp/kvset.rs
index 7166f59..6cb38a5 100644
--- a/csf/src/fp/kvset.rs
+++ b/csf/src/fp/kvset.rs
@@ -25,6 +25,14 @@ pub trait KVSet<K> {
     /// If `self` doesn't remember which keys are retained it uses `retained_hint` to check this.
     fn for_each_key_value<F>(&self, f: F/*, retained_hint: P*/) where F: FnMut(&K, u8)/*, P: FnMut(&K) -> bool*/;
 
+    /// Call `f` for each key in the set, using single thread.
+    ///
+    /// If `self` doesn't remember which keys are retained it uses `retained_hint` to check this.
+    #[inline(always)]
+    fn for_each_key<F>(&self, mut f: F/*, retained_hint: P*/) where F: FnMut(&K)/*, P: FnMut(&K) -> bool*/ {
+        self.for_each_key_value(|k, _| f(k));
+    }
+
     /// Call `collision_solver.process_value(key_to_index(key), value, self.bits_per_value())` for each `key`-`value` pair.
     #[inline]
     fn process_all_values<I, CS>(&self, mut key_to_index: I, collision_solver: &mut CS)
diff --git a/csf/src/fp/map/mod.rs b/csf/src/fp/map/mod.rs
index 9843fd1..5926092 100644
--- a/csf/src/fp/map/mod.rs
+++ b/csf/src/fp/map/mod.rs
@@ -131,11 +131,7 @@ impl<S: BuildSeededHasher> Map<S> {
         bits_per_value: u8,
         construct_partial: bool
     ) -> Arrays
-        where K: Hash,
-              KV: KVSet<K>,
-              LSC: LevelSizer,
-              CSB: CollisionSolverBuilder,
-              BS: stats::BuildStatsCollector
+        where K: Hash, KV: KVSet<K>, LSC: LevelSizer, CSB: CollisionSolverBuilder, BS: stats::BuildStatsCollector
     {
         let mut res = Arrays::default();
         let mut input_size = kv.kv_len();