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Code Issues 1 Projects Releases Wiki Activity Actions 9

[map] Resize map on long chain probes

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This commit is contained in:
Behdad Esfahbod 2023-05-26 15:56:30 -06:00
parent a652281ed6
commit 5abe713203
1 changed files with 9 additions and 0 deletions
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9
src/hb-map.hh
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@ -110,6 +110,7 @@ struct hb_hashmap_t
unsigned int occupancy; /* Including tombstones. */
unsigned int mask;
unsigned int prime;
unsigned int max_chain_length;
item_t *items;
friend void swap (hb_hashmap_t& a, hb_hashmap_t& b)
@ -123,6 +124,7 @@ struct hb_hashmap_t
hb_swap (a.occupancy, b.occupancy);
hb_swap (a.mask, b.mask);
hb_swap (a.prime, b.prime);
hb_swap (a.max_chain_length, b.max_chain_length);
hb_swap (a.items, b.items);
}
void init ()
@ -133,6 +135,7 @@ struct hb_hashmap_t
population = occupancy = 0;
mask = 0;
prime = 0;
max_chain_length = 0;
items = nullptr;
}
void fini ()
@ -181,6 +184,7 @@ struct hb_hashmap_t
population = occupancy = 0;
mask = new_size - 1;
prime = prime_for (power);
max_chain_length = power * 2;
items = new_items;
/* Insert back old items. */
@ -209,6 +213,7 @@ struct hb_hashmap_t
hash &= 0x3FFFFFFF; // We only store lower 30bit of hash
unsigned int tombstone = (unsigned int) -1;
unsigned int i = hash % prime;
unsigned length = 0;
unsigned step = 0;
while (items[i].is_used ())
{
@ -218,6 +223,7 @@ struct hb_hashmap_t
if (items[i].is_tombstone () && tombstone == (unsigned) -1)
tombstone = i;
i = (i + ++step) & mask;
length++;
}
item_t &item = items[tombstone == (unsigned) -1 ? i : tombstone];
@ -238,6 +244,9 @@ struct hb_hashmap_t
occupancy++;
population++;
if (unlikely (length > max_chain_length) && occupancy * 8 > mask)
resize (mask - 8); // This ensures we jump to next larger size
return true;
}