Commit ad708d70c9d5dc0553e4caa6097b150f6e6843e9
2023-05-11T17:41:49
[cache] Revise the dynamic hash table accounting. Instead of counting entries relative to the middle of the hash table, this switches to the absolute counter with the full index range mask. As a result, some calculations become a bit simpler. The cache resizing logic stays largely the same. * src/cache/ftccache.h (FTC_NODE_TOP_FOR_HASH): Revised with new counter. * src/cache/ftccache.c (ftc_get_top_node_for_hash): Ditto. (ftc_cache_resize): Simplify reallocations and stop their zeroing. (ftc_cache_init): Stop over-allocating but keep zeroing initially. (FTC_Cache_Clear, FTC_Cache_RemoveFaceID): Updated accordingly.
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diff --git a/src/cache/ftccache.c b/src/cache/ftccache.c
index ef7369d..e77c146 100644
--- a/src/cache/ftccache.c
+++ b/src/cache/ftccache.c
@@ -94,8 +94,8 @@
idx = hash & cache->mask;
- if ( idx < cache->p )
- idx = hash & ( 2 * cache->mask + 1 );
+ if ( idx >= cache->p )
+ idx = hash & ( cache->mask >> 1 );
return cache->buckets + idx;
}
@@ -113,9 +113,9 @@
for (;;)
{
FTC_Node node, *pnode;
- FT_UFast p = cache->p;
- FT_UFast mask = cache->mask;
- FT_UFast count = mask + p + 1; /* number of buckets */
+ FT_UFast p = cache->p;
+ FT_UFast size = cache->mask + 1; /* available size */
+ FT_UFast half = size >> 1;
/* do we need to expand the buckets array? */
@@ -127,20 +127,22 @@
/* try to expand the buckets array _before_ splitting
* the bucket lists
*/
- if ( p >= mask )
+ if ( p == size )
{
FT_Memory memory = cache->memory;
FT_Error error;
/* if we can't expand the array, leave immediately */
- if ( FT_RENEW_ARRAY( cache->buckets,
- ( mask + 1 ) * 2, ( mask + 1 ) * 4 ) )
+ if ( FT_QRENEW_ARRAY( cache->buckets, size, size * 2 ) )
break;
+
+ cache->mask = 2 * size - 1;
+ half = size;
}
- /* split a single bucket */
- pnode = cache->buckets + p;
+ /* the bucket to split */
+ pnode = cache->buckets + p - half;
for (;;)
{
@@ -148,7 +150,7 @@
if ( !node )
break;
- if ( node->hash & ( mask + 1 ) )
+ if ( node->hash & half )
{
*pnode = node->link;
node->link = new_list;
@@ -158,56 +160,50 @@
pnode = &node->link;
}
- cache->buckets[p + mask + 1] = new_list;
+ cache->buckets[p] = new_list;
cache->slack += FTC_HASH_MAX_LOAD;
+ cache->p = p + 1;
- if ( p >= mask )
- {
- cache->mask = 2 * mask + 1;
- cache->p = 0;
- }
- else
- cache->p = p + 1;
+ FT_TRACE2(( "ftc_cache_resize: cache %u increased to %u hashes\n",
+ cache->index, cache->p ));
}
/* do we need to shrink the buckets array? */
- else if ( cache->slack > (FT_Long)count * FTC_HASH_SUB_LOAD )
+ else if ( cache->slack > (FT_Long)p * FTC_HASH_SUB_LOAD )
{
- FT_UFast old_index = p + mask;
- FTC_Node* pold;
+ FTC_Node old_list = cache->buckets[--p];
- if ( old_index + 1 <= FTC_HASH_INITIAL_SIZE )
+ if ( p < FTC_HASH_INITIAL_SIZE )
break;
- if ( p == 0 )
+ if ( p == half )
{
FT_Memory memory = cache->memory;
FT_Error error;
/* if we can't shrink the array, leave immediately */
- if ( FT_QRENEW_ARRAY( cache->buckets,
- ( mask + 1 ) * 2, mask + 1 ) )
+ if ( FT_QRENEW_ARRAY( cache->buckets, size, half ) )
break;
- cache->mask >>= 1;
- p = cache->mask;
+ cache->mask = half - 1;
}
- else
- p--;
- pnode = cache->buckets + p;
+ /* the bucket to merge */
+ pnode = cache->buckets + p - half;
+
while ( *pnode )
pnode = &(*pnode)->link;
- pold = cache->buckets + old_index;
- *pnode = *pold;
- *pold = NULL;
+ *pnode = old_list;
cache->slack -= FTC_HASH_MAX_LOAD;
cache->p = p;
+
+ FT_TRACE2(( "ftc_cache_resize: cache %u decreased to %u hashes\n",
+ cache->index, cache->p ));
}
/* otherwise, the hash table is balanced */
@@ -336,11 +332,11 @@
FT_Error error;
- cache->p = 0;
+ cache->p = FTC_HASH_INITIAL_SIZE;
cache->mask = FTC_HASH_INITIAL_SIZE - 1;
cache->slack = FTC_HASH_INITIAL_SIZE * FTC_HASH_MAX_LOAD;
- FT_MEM_NEW_ARRAY( cache->buckets, FTC_HASH_INITIAL_SIZE * 2 );
+ FT_MEM_NEW_ARRAY( cache->buckets, FTC_HASH_INITIAL_SIZE );
return error;
}
@@ -351,11 +347,9 @@
if ( cache && cache->buckets )
{
FTC_Manager manager = cache->manager;
+ FT_UFast count = cache->p;
FT_UFast i;
- FT_UFast count;
-
- count = cache->p + cache->mask + 1;
for ( i = 0; i < count; i++ )
{
@@ -562,12 +556,12 @@
FTC_Cache_RemoveFaceID( FTC_Cache cache,
FTC_FaceID face_id )
{
- FT_UFast i, count;
FTC_Manager manager = cache->manager;
FTC_Node frees = NULL;
+ FT_UFast count = cache->p;
+ FT_UFast i;
- count = cache->p + cache->mask + 1;
for ( i = 0; i < count; i++ )
{
FTC_Node* pnode = cache->buckets + i;
diff --git a/src/cache/ftccache.h b/src/cache/ftccache.h
index 23bcb65..850d255 100644
--- a/src/cache/ftccache.h
+++ b/src/cache/ftccache.h
@@ -72,11 +72,12 @@ FT_BEGIN_HEADER
#define FTC_NODE_NEXT( x ) FTC_NODE( (x)->mru.next )
#define FTC_NODE_PREV( x ) FTC_NODE( (x)->mru.prev )
+ /* address the hash table entries */
#ifdef FTC_INLINE
-#define FTC_NODE_TOP_FOR_HASH( cache, hash ) \
- ( ( cache )->buckets + \
- ( ( ( ( hash ) & ( cache )->mask ) < ( cache )->p ) \
- ? ( ( hash ) & ( ( cache )->mask * 2 + 1 ) ) \
+#define FTC_NODE_TOP_FOR_HASH( cache, hash ) \
+ ( ( cache )->buckets + \
+ ( ( ( ( hash ) & ( cache )->mask ) >= ( cache )->p ) \
+ ? ( ( hash ) & ( ( cache )->mask >> 1 ) ) \
: ( ( hash ) & ( cache )->mask ) ) )
#else
FT_LOCAL( FTC_Node* )
@@ -139,11 +140,13 @@ FT_BEGIN_HEADER
} FTC_CacheClassRec;
- /* each cache really implements a dynamic hash table to manage its nodes */
+ /* each cache really implements a hash table to manage its nodes */
+ /* the number of the table entries (buckets) can change dynamically */
+ /* each bucket contains a linked lists of nodes for a given hash */
typedef struct FTC_CacheRec_
{
- FT_UFast p;
- FT_UFast mask;
+ FT_UFast p; /* hash table counter */
+ FT_UFast mask; /* hash table index range */
FT_Long slack;
FTC_Node* buckets;