diff --git a/eth2/fork_choice/Cargo.toml b/eth2/fork_choice/Cargo.toml
index 210f3c235..819b84055 100644
--- a/eth2/fork_choice/Cargo.toml
+++ b/eth2/fork_choice/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2018"
 db = { path = "../../beacon_node/db" }
 ssz = { path = "../utils/ssz" }
 types = { path = "../types" }
-fast-math = "0.1.1"
 log = "0.4.6"
 bit-vec = "0.5.0"
 
diff --git a/eth2/fork_choice/src/bitwise_lmd_ghost.rs b/eth2/fork_choice/src/bitwise_lmd_ghost.rs
index 1e66de079..60aa38fe7 100644
--- a/eth2/fork_choice/src/bitwise_lmd_ghost.rs
+++ b/eth2/fork_choice/src/bitwise_lmd_ghost.rs
@@ -1,5 +1,5 @@
+//! The optimised bitwise LMD-GHOST fork choice rule.
 extern crate bit_vec;
-extern crate fast_math;
 
 use crate::{ForkChoice, ForkChoiceError};
 use bit_vec::BitVec;
@@ -7,7 +7,6 @@ use db::{
     stores::{BeaconBlockStore, BeaconStateStore},
     ClientDB,
 };
-use fast_math::log2_raw;
 use log::{debug, trace};
 use std::collections::HashMap;
 use std::sync::Arc;
@@ -19,33 +18,28 @@ use types::{
 //TODO: Pruning - Children
 //TODO: Handle Syncing
 
-/// The optimised bitwise LMD-GHOST fork choice rule.
-/// NOTE: This uses u32 to represent difference between block heights. Thus this is only
-/// applicable for block height differences in the range of a u32.
-/// This can potentially be parallelized in some parts.
-// we use fast log2, a log2 lookup table is implemented in Vitaliks code, potentially do
-// the comparison. Log2_raw takes 2ns according to the documentation.
+// NOTE: This uses u32 to represent difference between block heights. Thus this is only
+// applicable for block height differences in the range of a u32.
+// This can potentially be parallelized in some parts.
+
+/// Compute the base-2 logarithm of an integer, floored (rounded down)
 #[inline]
-fn log2_int(x: u32) -> u32 {
+fn log2_int(x: u64) -> u32 {
     if x == 0 {
         return 0;
     }
-    assert!(
-        x <= std::f32::MAX as u32,
-        "Height too large for fast log in bitwise fork choice"
-    );
-    log2_raw(x as f32) as u32
+    63 - x.leading_zeros()
 }
 
-fn power_of_2_below(x: u32) -> u32 {
-    2u32.pow(log2_int(x))
+fn power_of_2_below(x: u64) -> u64 {
+    2u64.pow(log2_int(x))
 }
 
 /// Stores the necessary data structures to run the optimised bitwise lmd ghost algorithm.
 pub struct BitwiseLMDGhost<T: ClientDB + Sized> {
     /// A cache of known ancestors at given heights for a specific block.
     //TODO: Consider FnvHashMap
-    cache: HashMap<CacheKey<u32>, Hash256>,
+    cache: HashMap<CacheKey<u64>, Hash256>,
     /// Log lookup table for blocks to their ancestors.
     //TODO: Verify we only want/need a size 16 log lookup
     ancestors: Vec<HashMap<Hash256, Hash256>>,
@@ -147,7 +141,7 @@ where
             }
         }
         // check if the result is stored in our cache
-        let cache_key = CacheKey::new(&block_hash, target_height.as_u32());
+        let cache_key = CacheKey::new(&block_hash, target_height.as_u64());
         if let Some(ancestor) = self.cache.get(&cache_key) {
             return Some(*ancestor);
         }
@@ -155,7 +149,7 @@ where
         // not in the cache recursively search for ancestors using a log-lookup
         if let Some(ancestor) = {
             let ancestor_lookup = self.ancestors
-                [log2_int((block_height - target_height - 1u64).as_u32()) as usize]
+                [log2_int((block_height - target_height - 1u64).as_u64()) as usize]
                 .get(&block_hash)
                 //TODO: Panic if we can't lookup and fork choice fails
                 .expect("All blocks should be added to the ancestor log lookup table");
@@ -380,7 +374,7 @@ impl<T: ClientDB + Sized> ForkChoice for BitwiseLMDGhost<T> {
             // logarithmic lookup blocks to see if there are obvious winners, if so,
             // progress to the next iteration.
             let mut step =
-                power_of_2_below(self.max_known_height.saturating_sub(block_height).as_u32()) / 2;
+                power_of_2_below(self.max_known_height.saturating_sub(block_height).as_u64()) / 2;
             while step > 0 {
                 trace!("Current Step: {}", step);
                 if let Some(clear_winner) = self.get_clear_winner(
@@ -469,7 +463,6 @@ mod tests {
 
     #[test]
     pub fn test_power_of_2_below() {
-        println!("{:?}", std::f32::MAX);
         assert_eq!(power_of_2_below(4), 4);
         assert_eq!(power_of_2_below(5), 4);
         assert_eq!(power_of_2_below(7), 4);
@@ -478,4 +471,12 @@ mod tests {
         assert_eq!(power_of_2_below(33), 32);
         assert_eq!(power_of_2_below(63), 32);
     }
+
+    #[test]
+    pub fn test_power_of_2_below_large() {
+        let pow: u64 = 1 << 24;
+        for x in (pow - 20)..(pow + 20) {
+            assert!(power_of_2_below(x) <= x, "{}", x);
+        }
+    }
 }
diff --git a/eth2/types/src/slot_height.rs b/eth2/types/src/slot_height.rs
index afa0ff775..f9370f485 100644
--- a/eth2/types/src/slot_height.rs
+++ b/eth2/types/src/slot_height.rs
@@ -13,7 +13,6 @@ use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Rem, Sub, SubAssi
 pub struct SlotHeight(u64);
 
 impl_common!(SlotHeight);
-impl_into_u32!(SlotHeight); // SlotHeight can be converted to u32
 
 impl SlotHeight {
     pub fn new(slot: u64) -> SlotHeight {
diff --git a/eth2/utils/ssz_derive/src/lib.rs b/eth2/utils/ssz_derive/src/lib.rs
index ac66526fe..f71bff709 100644
--- a/eth2/utils/ssz_derive/src/lib.rs
+++ b/eth2/utils/ssz_derive/src/lib.rs
@@ -147,12 +147,12 @@ pub fn ssz_tree_hash_derive(input: TokenStream) -> TokenStream {
     let output = quote! {
         impl ssz::TreeHash for #name {
             fn hash_tree_root_internal(&self) -> Vec<u8> {
-                let mut result: Vec<u8> = vec![];
+                let mut list: Vec<Vec<u8>> = Vec::new();
                 #(
-                    result.append(&mut self.#field_idents.hash_tree_root_internal());
+                    list.push(self.#field_idents.hash_tree_root_internal());
                 )*
 
-                ssz::hash(&result)
+                ssz::merkle_hash(&mut list)
             }
         }
     };