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More efficient hash table thawing

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* src/fns.c (hash_table_thaw): Don't allocate anything for empty
tables.  Don't initialise the next vector twice.
(maybe_resize_hash_table): Factor out min_size constant.
This commit is contained in:
Mattias Engdegård 2024-01-15 10:58:59 +01:00
parent 0b8fe3c73c
commit dc404c5d0c
1 changed files with 33 additions and 23 deletions
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56
src/fns.c
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@ -4665,11 +4665,12 @@ maybe_resize_hash_table (struct Lisp_Hash_Table *h)
if (h->next_free < 0)
{
ptrdiff_t old_size = HASH_TABLE_SIZE (h);
ptrdiff_t base_size = min (max (old_size, 8), PTRDIFF_MAX / 2);
ptrdiff_t min_size = 8;
ptrdiff_t base_size = min (max (old_size, min_size), PTRDIFF_MAX / 2);
/* Grow aggressively at small sizes, then just double. */
ptrdiff_t new_size =
old_size == 0
? 8
? min_size
: (base_size <= 64 ? base_size * 4 : base_size * 2);
/* Allocate all the new vectors before updating *H, to
@ -4754,30 +4755,39 @@ hash_table_thaw (Lisp_Object hash_table)
h->test = hash_table_test_from_std (h->frozen_test);
ptrdiff_t size = h->count;
h->table_size = size;
ptrdiff_t index_size = hash_index_size (size);
h->index_size = index_size;
h->next_free = -1;
h->hash = hash_table_alloc_bytes (size * sizeof *h->hash);
h->next = hash_table_alloc_bytes (size * sizeof *h->next);
for (ptrdiff_t i = 0; i < size; i++)
h->next[i] = -1;
h->index = hash_table_alloc_bytes (index_size * sizeof *h->index);
for (ptrdiff_t i = 0; i < index_size; i++)
h->index[i] = -1;
/* Recompute the actual hash codes for each entry in the table.
Order is still invalid. */
for (ptrdiff_t i = 0; i < size; i++)
if (size == 0)
{
Lisp_Object key = HASH_KEY (h, i);
hash_hash_t hash_code = hash_from_key (h, key);
ptrdiff_t start_of_bucket = hash_index_index (h, hash_code);
set_hash_hash_slot (h, i, hash_code);
set_hash_next_slot (h, i, HASH_INDEX (h, start_of_bucket));
set_hash_index_slot (h, start_of_bucket, i);
h->key_and_value = NULL;
h->hash = NULL;
h->next = NULL;
h->index_size = 1;
h->index = (hash_idx_t *)empty_hash_index_vector;
}
else
{
ptrdiff_t index_size = hash_index_size (size);
h->index_size = index_size;
h->hash = hash_table_alloc_bytes (size * sizeof *h->hash);
h->next = hash_table_alloc_bytes (size * sizeof *h->next);
h->index = hash_table_alloc_bytes (index_size * sizeof *h->index);
for (ptrdiff_t i = 0; i < index_size; i++)
h->index[i] = -1;
/* Recompute the hash codes for each entry in the table. */
for (ptrdiff_t i = 0; i < size; i++)
{
Lisp_Object key = HASH_KEY (h, i);
hash_hash_t hash_code = hash_from_key (h, key);
ptrdiff_t start_of_bucket = hash_index_index (h, hash_code);
set_hash_hash_slot (h, i, hash_code);
set_hash_next_slot (h, i, HASH_INDEX (h, start_of_bucket));
set_hash_index_slot (h, start_of_bucket, i);
}
}
}