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hashmap: new load_factor and optimizations
This commit is contained in:
ka-weihe
Alexander Medvednikov
parent
bf6b206fca
commit
31899eac2a
@ -4,31 +4,20 @@
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module hashmap
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const (
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initial_size = 2<<4
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initial_size = 2 << 4
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initial_cap = initial_size - 1
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load_factor = 0.5
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probe_offset = u16(256)
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load_factor = 0.8
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)
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// hash-function should not be in this file
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const (
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fnv64_prime = 1099511628211
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fnv64_offset_basis = 14695981039346656037
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fnv32_offset_basis = u32(2166136261)
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fnv32_prime = u32(16777619)
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)
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pub struct Hashmap {
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mut:
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info &u16
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key_values &KeyValue
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cap int
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pub mut:
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size int
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}
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struct KeyValue {
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key string
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mut:
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value int
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}
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[inline]
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fn fnv1a64(data string) u64 {
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mut hash := fnv64_offset_basis
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@ -38,11 +27,28 @@ fn fnv1a64(data string) u64 {
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return hash
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}
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pub struct Hashmap {
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mut:
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info &u16
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key_values &KeyValue
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cap int
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pub mut:
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load_factor f32
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size int
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}
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struct KeyValue {
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key string
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mut:
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value int
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}
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pub fn new_hashmap() Hashmap {
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return Hashmap{
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info: &u16(calloc(sizeof(u16) * initial_size))
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key_values: &KeyValue(calloc(sizeof(KeyValue) * initial_size))
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cap: initial_cap
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load_factor: 0.8
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size: 0
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}
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}
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@ -51,12 +57,12 @@ pub fn (h mut Hashmap) set(key string, value int) {
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// The load factor is 0.5.
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// It will be adjustable in the future and with
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// a higher default settings to lower memory usage.
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if (h.size<<1) == (h.cap - 1) {
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if (f32(h.size) / f32(h.cap)) > h.load_factor {
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h.rehash()
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}
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// Hash-function will be swapped for wyhash
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hash := fnv1a64(key)
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mut info := u16((hash>>56) | probe_offset)
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mut info := u16((hash >> 56) | probe_offset)
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mut index := hash & h.cap
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// While probe count is less
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for info < h.info[index] {
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@ -75,18 +81,17 @@ pub fn (h mut Hashmap) set(key string, value int) {
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// Match is not possible anymore.
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// Probe until an empty index is found.
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// Swap when probe count is higher/richer (Robin Hood).
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mut current_key := key
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mut current_value := value
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mut current_kv := KeyValue{key, value}
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for h.info[index] != 0 {
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if info > h.info[index] {
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tmp_kv := h.key_values[index]
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// Swap info word
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tmp_info := h.info[index]
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h.key_values[index] = KeyValue{
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current_key,current_value}
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h.info[index] = info
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current_key = tmp_kv.key
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current_value = tmp_kv.value
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info = tmp_info
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// Swap KeyValue
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tmp_kv := h.key_values[index]
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h.key_values[index] = current_kv
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current_kv = tmp_kv
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}
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index = (index + 1) & h.cap
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info += probe_offset
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@ -94,56 +99,42 @@ pub fn (h mut Hashmap) set(key string, value int) {
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// Should almost never happen
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if (info & 0xFF00) == 0xFF00 {
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h.rehash()
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h.set(current_key, current_value)
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h.set(current_kv.key, current_kv.value)
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return
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}
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h.info[index] = info
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h.key_values[index] = KeyValue{
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current_key,current_value}
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h.key_values[index] = current_kv
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h.size++
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}
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fn (h mut Hashmap) rehash() {
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old_cap := h.cap
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h.cap = ((h.cap + 1)<<1) - 1
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h.cap = ((h.cap + 1) << 1) - 1
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mut new_key_values := &KeyValue(calloc(sizeof(KeyValue) * (h.cap + 1)))
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mut new_info := &u16(calloc(sizeof(u16) * (h.cap + 1)))
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for i in 0 .. (old_cap + 1) {
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if h.info[i] != 0 {
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key := h.key_values[i].key
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value := h.key_values[i].value
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hash := fnv1a64(key)
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mut info := u16((hash>>56) | probe_offset)
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mut kv := h.key_values[i]
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hash := fnv1a64(kv.key)
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mut info := u16((hash >> 56) | probe_offset)
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mut index := hash & h.cap
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// While probe count is less
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for info < new_info[index] {
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index = (index + 1) & h.cap
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info += probe_offset
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}
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// While we might have a match
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for info == new_info[index] {
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if key == new_key_values[index].key {
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new_key_values[index].value = value
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return
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}
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index = (index + 1) & h.cap
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info += probe_offset
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}
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// Match is not possible anymore.
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// Probe until an empty index is found.
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// Swap when probe count is higher/richer (Robin Hood).
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mut current_key := key
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mut current_value := value
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for new_info[index] != 0 {
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if info > new_info[index] {
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tmp_kv := new_key_values[index]
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// Swap info word
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tmp_info := new_info[index]
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new_key_values[index] = KeyValue{
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current_key,current_value}
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new_info[index] = info
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current_key = tmp_kv.key
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current_value = tmp_kv.value
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info = tmp_info
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// Swap KeyValue
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tmp_kv := new_key_values[index]
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new_key_values[index] = kv
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kv = tmp_kv
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}
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index = (index + 1) & h.cap
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info += probe_offset
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@ -151,12 +142,11 @@ fn (h mut Hashmap) rehash() {
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// Should almost never happen
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if (info & 0xFF00) == 0xFF00 {
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h.rehash()
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h.set(current_key, current_value)
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h.set(kv.key, kv.value)
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return
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}
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new_info[index] = info
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new_key_values[index] = KeyValue{
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current_key,current_value}
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new_key_values[index] = kv
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}
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}
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h.key_values = new_key_values
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@ -166,7 +156,7 @@ fn (h mut Hashmap) rehash() {
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pub fn (h mut Hashmap) delete(key string) {
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hash := fnv1a64(key)
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mut index := hash & h.cap
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mut info := u16((hash>>56) | probe_offset)
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mut info := u16((hash >> 56) | probe_offset)
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for info < h.info[index] {
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index = (index + 1) & h.cap
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info += probe_offset
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@ -177,7 +167,7 @@ pub fn (h mut Hashmap) delete(key string) {
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mut old_index := index
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index = (index + 1) & h.cap
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mut current_info := h.info[index]
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for (current_info>>8) > 1 {
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for (current_info >> 8) > 1 {
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h.info[old_index] = current_info - probe_offset
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h.key_values[old_index] = h.key_values[index]
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old_index = index
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@ -196,7 +186,7 @@ pub fn (h mut Hashmap) delete(key string) {
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pub fn (h Hashmap) get(key string) int {
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hash := fnv1a64(key)
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mut index := hash & h.cap
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mut info := u16((hash>>56) | probe_offset)
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mut info := u16((hash >> 56) | probe_offset)
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for info < h.info[index] {
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index = (index + 1) & h.cap
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info += probe_offset
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@ -214,7 +204,7 @@ pub fn (h Hashmap) get(key string) int {
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pub fn (h Hashmap) exists(key string) bool {
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hash := fnv1a64(key)
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mut index := hash & h.cap
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mut info := u16((hash>>56) | probe_offset)
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mut info := u16((hash >> 56) | probe_offset)
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for info < h.info[index] {
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index = (index + 1) & h.cap
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info += probe_offset
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@ -230,8 +220,7 @@ pub fn (h Hashmap) exists(key string) bool {
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}
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pub fn (h Hashmap) keys() []string {
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size := h.size
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mut keys := [''].repeat(size)
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mut keys := [''].repeat(h.size)
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mut j := 0
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for i in 0 .. (h.cap + 1) {
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if h.info[i] != 0 {
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