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#124 improve map rehashing
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@SanderMertens
SanderMertens committed May 22, 2022
1 parent a2d2fee commit d26cd43
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Showing 4 changed files with 79 additions and 73 deletions.
75 changes: 39 additions & 36 deletions flecs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12440,7 +12440,7 @@ int32_t ecs_strbuf_written(

/* The ratio used to determine whether the map should rehash. If
* (element_count * LOAD_FACTOR) > bucket_count, bucket count is increased. */
#define LOAD_FACTOR (1.5f)
#define LOAD_FACTOR (1.2f)
#define KEY_SIZE (ECS_SIZEOF(ecs_map_key_t))
#define GET_ELEM(array, elem_size, index) \
ECS_OFFSET(array, (elem_size) * (index))
Expand Down Expand Up @@ -12571,19 +12571,18 @@ int32_t add_to_bucket(
const void *payload)
{
int32_t index = bucket->count ++;
int32_t bucket_count = index + 1;
int32_t count = index + 1;

bucket->keys = ecs_os_realloc_n(bucket->keys, ecs_map_key_t, count);
if (elem_size) {
bucket->payload = ecs_os_realloc(bucket->payload, elem_size * count);
}

bucket->keys = ecs_os_realloc(bucket->keys, KEY_SIZE * bucket_count);
bucket->keys[index] = key;

if (elem_size) {
bucket->payload = ecs_os_realloc(bucket->payload, elem_size * bucket_count);
if (payload) {
void *elem = GET_ELEM(bucket->payload, elem_size, index);
ecs_os_memcpy(elem, payload, elem_size);
}
} else {
bucket->payload = NULL;
if (elem_size && payload) {
void *elem = GET_ELEM(bucket->payload, elem_size, index);
ecs_os_memcpy(elem, payload, elem_size);
}

return index;
Expand Down Expand Up @@ -12642,44 +12641,48 @@ void rehash(
ecs_assert(bucket_count != 0, ECS_INTERNAL_ERROR, NULL);
ecs_assert(bucket_count > map->bucket_count, ECS_INTERNAL_ERROR, NULL);

ensure_buckets(map, bucket_count);

ecs_bucket_t *buckets = map->buckets;
ecs_assert(buckets != NULL, ECS_INTERNAL_ERROR, NULL);
ecs_bucket_t *old_buckets = map->buckets;
ecs_size_t elem_size = map->elem_size;
uint16_t bucket_shift = map->bucket_shift;
int32_t bucket_id;

/* Iterate backwards as elements could otherwise be moved to existing
* buckets which could temporarily cause the number of elements in a
* bucket to exceed BUCKET_COUNT. */
for (bucket_id = bucket_count - 1; bucket_id >= 0; bucket_id --) {
ecs_bucket_t *bucket = &buckets[bucket_id];
int32_t b, old_count = map->bucket_count;
int32_t new_count = flecs_next_pow_of_2(bucket_count);

map->buckets = ecs_os_calloc_n(ecs_bucket_t, new_count);
map->bucket_count = new_count;
uint8_t bucket_shift = map->bucket_shift = get_bucket_shift(new_count);

for (b = 0; b < old_count; b ++) {
ecs_bucket_t *old = &old_buckets[b];

int i, count = bucket->count;
ecs_map_key_t *key_array = bucket->keys;
void *payload_array = bucket->payload;
int i, count = old->count;
ecs_map_key_t *keys = old->keys;
void *payload = old->payload;

for (i = 0; i < count; i ++) {
ecs_map_key_t key = key_array[i];
void *elem = GET_ELEM(payload_array, elem_size, i);
ecs_map_key_t key = keys[i];
void *elem = GET_ELEM(payload, elem_size, i);
int32_t new_bucket_id = get_bucket_index(map, bucket_shift, key);

if (new_bucket_id != bucket_id) {
ecs_bucket_t *new_bucket = &buckets[new_bucket_id];
ecs_bucket_t *new_bucket = &map->buckets[new_bucket_id];

if (count == 1 && !new_bucket->count) {
new_bucket->keys = keys;
new_bucket->payload = payload;
new_bucket->count = 1;
keys = NULL;
payload = NULL;
} else {
add_to_bucket(new_bucket, elem_size, key, elem);
remove_from_bucket(bucket, elem_size, key, i);

count --;
i --;
}
}

if (!bucket->count) {
clear_bucket(bucket);
if (count) {
ecs_os_free(keys);
ecs_os_free(payload);
}
}

ecs_os_free(old_buckets);
}

void _ecs_map_init(
Expand Down Expand Up @@ -39368,7 +39371,7 @@ void ecs_table_cache_init(
ecs_table_cache_t *cache)
{
ecs_assert(cache != NULL, ECS_INTERNAL_ERROR, NULL);
ecs_map_init(&cache->index, ecs_table_cache_hdr_t*, 0);
ecs_map_init(&cache->index, ecs_table_cache_hdr_t*, 4);
}

void ecs_table_cache_fini(
Expand Down
73 changes: 38 additions & 35 deletions src/datastructures/map.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@

/* The ratio used to determine whether the map should rehash. If
* (element_count * LOAD_FACTOR) > bucket_count, bucket count is increased. */
#define LOAD_FACTOR (1.5f)
#define LOAD_FACTOR (1.2f)
#define KEY_SIZE (ECS_SIZEOF(ecs_map_key_t))
#define GET_ELEM(array, elem_size, index) \
ECS_OFFSET(array, (elem_size) * (index))
Expand Down Expand Up @@ -134,19 +134,18 @@ int32_t add_to_bucket(
const void *payload)
{
int32_t index = bucket->count ++;
int32_t bucket_count = index + 1;
int32_t count = index + 1;

bucket->keys = ecs_os_realloc_n(bucket->keys, ecs_map_key_t, count);
if (elem_size) {
bucket->payload = ecs_os_realloc(bucket->payload, elem_size * count);
}

bucket->keys = ecs_os_realloc(bucket->keys, KEY_SIZE * bucket_count);
bucket->keys[index] = key;

if (elem_size) {
bucket->payload = ecs_os_realloc(bucket->payload, elem_size * bucket_count);
if (payload) {
void *elem = GET_ELEM(bucket->payload, elem_size, index);
ecs_os_memcpy(elem, payload, elem_size);
}
} else {
bucket->payload = NULL;
if (elem_size && payload) {
void *elem = GET_ELEM(bucket->payload, elem_size, index);
ecs_os_memcpy(elem, payload, elem_size);
}

return index;
Expand Down Expand Up @@ -205,44 +204,48 @@ void rehash(
ecs_assert(bucket_count != 0, ECS_INTERNAL_ERROR, NULL);
ecs_assert(bucket_count > map->bucket_count, ECS_INTERNAL_ERROR, NULL);

ensure_buckets(map, bucket_count);

ecs_bucket_t *buckets = map->buckets;
ecs_assert(buckets != NULL, ECS_INTERNAL_ERROR, NULL);
ecs_bucket_t *old_buckets = map->buckets;
ecs_size_t elem_size = map->elem_size;
uint16_t bucket_shift = map->bucket_shift;
int32_t bucket_id;

/* Iterate backwards as elements could otherwise be moved to existing
* buckets which could temporarily cause the number of elements in a
* bucket to exceed BUCKET_COUNT. */
for (bucket_id = bucket_count - 1; bucket_id >= 0; bucket_id --) {
ecs_bucket_t *bucket = &buckets[bucket_id];
int32_t b, old_count = map->bucket_count;
int32_t new_count = flecs_next_pow_of_2(bucket_count);

map->buckets = ecs_os_calloc_n(ecs_bucket_t, new_count);
map->bucket_count = new_count;
uint8_t bucket_shift = map->bucket_shift = get_bucket_shift(new_count);

for (b = 0; b < old_count; b ++) {
ecs_bucket_t *old = &old_buckets[b];

int i, count = bucket->count;
ecs_map_key_t *key_array = bucket->keys;
void *payload_array = bucket->payload;
int i, count = old->count;
ecs_map_key_t *keys = old->keys;
void *payload = old->payload;

for (i = 0; i < count; i ++) {
ecs_map_key_t key = key_array[i];
void *elem = GET_ELEM(payload_array, elem_size, i);
ecs_map_key_t key = keys[i];
void *elem = GET_ELEM(payload, elem_size, i);
int32_t new_bucket_id = get_bucket_index(map, bucket_shift, key);

if (new_bucket_id != bucket_id) {
ecs_bucket_t *new_bucket = &buckets[new_bucket_id];
ecs_bucket_t *new_bucket = &map->buckets[new_bucket_id];

if (count == 1 && !new_bucket->count) {
new_bucket->keys = keys;
new_bucket->payload = payload;
new_bucket->count = 1;
keys = NULL;
payload = NULL;
} else {
add_to_bucket(new_bucket, elem_size, key, elem);
remove_from_bucket(bucket, elem_size, key, i);

count --;
i --;
}
}

if (!bucket->count) {
clear_bucket(bucket);
if (count) {
ecs_os_free(keys);
ecs_os_free(payload);
}
}

ecs_os_free(old_buckets);
}

void _ecs_map_init(
Expand Down
2 changes: 1 addition & 1 deletion src/table_cache.c
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ void ecs_table_cache_init(
ecs_table_cache_t *cache)
{
ecs_assert(cache != NULL, ECS_INTERNAL_ERROR, NULL);
ecs_map_init(&cache->index, ecs_table_cache_hdr_t*, 0);
ecs_map_init(&cache->index, ecs_table_cache_hdr_t*, 4);
}

void ecs_table_cache_fini(
Expand Down
2 changes: 1 addition & 1 deletion test/collections/src/Map.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,7 @@ void Map_set_rehash() {
ecs_map_set(map, i + 1000000, &(char*){"yyy"});
}

test_int(ecs_map_bucket_count(map), 64);
test_int(ecs_map_bucket_count(map), 32);
test_str(ecs_map_get_ptr(map, char*, 1 + 1000000), "yyy");
test_str(ecs_map_get_ptr(map, char*, 2 + 1000000), "yyy");
test_str(ecs_map_get_ptr(map, char*, 3 + 1000000), "yyy");
Expand Down

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