hashmap: new load_factor and optimizations

vlib/builtin/hashmap/hashmap.v

@@ -6,29 +6,18 @@ module hashmap
 const (
 	initial_size = 2 << 4
 	initial_cap = initial_size - 1
-	load_factor = 0.5
 	probe_offset = u16(256)
+	load_factor = 0.8
+)
+
+// hash-function should not be in this file
+const (
 	fnv64_prime = 1099511628211
 	fnv64_offset_basis = 14695981039346656037
 	fnv32_offset_basis = u32(2166136261)
 	fnv32_prime = u32(16777619)
 )
 
-pub struct Hashmap {
-mut:
-	info       &u16
-	key_values &KeyValue
-	cap        int
-pub mut:
-	size       int
-}
-
-struct KeyValue {
-	key   string
-mut:
-	value int
-}
-
 [inline]
 fn fnv1a64(data string) u64 {
 	mut hash := fnv64_offset_basis
@@ -38,11 +27,28 @@ fn fnv1a64(data string) u64 {
 	return hash
 }
 
+pub struct Hashmap {
+mut:
+	info        &u16
+	key_values  &KeyValue
+	cap         int
+pub mut:
+	load_factor f32
+	size        int
+}
+
+struct KeyValue {
+	key   string
+mut:
+	value int
+}
+
 pub fn new_hashmap() Hashmap {
 	return Hashmap{
 		info: &u16(calloc(sizeof(u16) * initial_size))
 		key_values: &KeyValue(calloc(sizeof(KeyValue) * initial_size))
 		cap: initial_cap
+		load_factor: 0.8
 		size: 0
 	}
 }
@@ -51,7 +57,7 @@ pub fn (h mut Hashmap) set(key string, value int) {
 	// The load factor is 0.5.
 	// It will be adjustable  in the future and with
 	// a higher default settings to lower memory usage.
-	if (h.size<<1) == (h.cap - 1) {
+	if (f32(h.size) / f32(h.cap)) > h.load_factor {
 		h.rehash()
 	}
 	// Hash-function will be swapped for wyhash
@@ -75,18 +81,17 @@ pub fn (h mut Hashmap) set(key string, value int) {
 	// Match is not possible anymore.
 	// Probe until an empty index is found.
 	// Swap when probe count is higher/richer (Robin Hood).
-	mut current_key := key
+	mut current_kv := KeyValue{key, value}
-	mut current_value := value
 	for h.info[index] != 0 {
 		if info > h.info[index] {
-			tmp_kv := h.key_values[index]
+			// Swap info word
 			tmp_info := h.info[index]
-			h.key_values[index] = KeyValue{
-				current_key,current_value}
 			h.info[index] = info
-			current_key = tmp_kv.key
-			current_value = tmp_kv.value
 			info = tmp_info
+			// Swap KeyValue
+			tmp_kv := h.key_values[index] 
+			h.key_values[index] = current_kv
+			current_kv = tmp_kv
 		}
 		index = (index + 1) & h.cap
 		info += probe_offset
@@ -94,12 +99,11 @@ pub fn (h mut Hashmap) set(key string, value int) {
 	// Should almost never happen
 	if (info & 0xFF00) == 0xFF00 {
 		h.rehash()
-		h.set(current_key, current_value)
+		h.set(current_kv.key, current_kv.value)
 		return
 	}
 	h.info[index] = info
-	h.key_values[index] = KeyValue{
+	h.key_values[index] = current_kv
-		current_key,current_value}
 	h.size++
 }
 
@@ -110,9 +114,8 @@ fn (h mut Hashmap) rehash() {
 	mut new_info := &u16(calloc(sizeof(u16) * (h.cap + 1)))
 	for i in 0 .. (old_cap + 1) {
 		if h.info[i] != 0 {
-			key := h.key_values[i].key
+			mut kv := h.key_values[i]
-			value := h.key_values[i].value
+			hash := fnv1a64(kv.key)
-			hash := fnv1a64(key)
 			mut info := u16((hash >> 56) | probe_offset)
 			mut index := hash & h.cap
 			// While probe count is less
@@ -120,30 +123,18 @@ fn (h mut Hashmap) rehash() {
 				index = (index + 1) & h.cap
 				info += probe_offset
 			}
-			// While we might have a match
-			for info == new_info[index] {
-				if key == new_key_values[index].key {
-					new_key_values[index].value = value
-					return
-				}
-				index = (index + 1) & h.cap
-				info += probe_offset
-			}
-			// Match is not possible anymore.
 			// Probe until an empty index is found.
 			// Swap when probe count is higher/richer (Robin Hood).
-			mut current_key := key
-			mut current_value := value
 			for new_info[index] != 0 {
 				if info > new_info[index] {
-					tmp_kv := new_key_values[index]
+					// Swap info word
 					tmp_info := new_info[index]
-					new_key_values[index] = KeyValue{
-						current_key,current_value}
 					new_info[index] = info
-					current_key = tmp_kv.key
-					current_value = tmp_kv.value
 					info = tmp_info
+					// Swap KeyValue
+					tmp_kv := new_key_values[index] 
+					new_key_values[index] = kv
+					kv = tmp_kv
 				}
 				index = (index + 1) & h.cap
 				info += probe_offset
@@ -151,12 +142,11 @@ fn (h mut Hashmap) rehash() {
 			// Should almost never happen
 			if (info & 0xFF00) == 0xFF00 {
 				h.rehash()
-				h.set(current_key, current_value)
+				h.set(kv.key, kv.value)
 				return
 			}
 			new_info[index] = info
-			new_key_values[index] = KeyValue{
+			new_key_values[index] = kv
-				current_key,current_value}
 		}
 	}
 	h.key_values = new_key_values
@@ -230,8 +220,7 @@ pub fn (h Hashmap) exists(key string) bool {
 }
 
 pub fn (h Hashmap) keys() []string {
-	size := h.size
+	mut keys := [''].repeat(h.size)
-	mut keys := [''].repeat(size)
 	mut j := 0
 	for i in 0 .. (h.cap + 1) {
 		if h.info[i] != 0 {