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new hash method for lua_Number (double) (due to a performance problem)

This commit is contained in:
Roberto Ierusalimschy 2003-03-24 11:18:42 -03:00
parent 80bac182db
commit b858161fbc
1 changed files with 38 additions and 15 deletions
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53
ltable.c
View File

@ -1,5 +1,5 @@
/* /*
** $Id: ltable.c,v 1.129 2003/03/18 12:50:04 roberto Exp roberto $ ** $Id: ltable.c,v 1.130 2003/03/20 20:26:33 roberto Exp roberto $
** Lua tables (hash) ** Lua tables (hash)
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -21,6 +21,7 @@
** performance penalties. ** performance penalties.
*/ */
#include <string.h>
#define ltable_c #define ltable_c
@ -54,17 +55,41 @@
#endif #endif
#define hashg(t,n) (gnode(t, lmod((n), sizenode(t)))) #define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
#define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
#define hashboolean(t,p) hashpow2(t, p)
#define hashnum(t,n) hashg(t, cast(lu_hash, cast(ls_hash, (n))))
#define hashstr(t,str) hashg(t, (str)->tsv.hash)
#define hashboolean(t,p) hashg(t, p)
/* /*
** avoid modulus by power of 2 for pointers, as they tend to have many ** for some types, it is better to avoid modulus by power of 2, as
** 2 factors. ** they tend to have many 2 factors.
*/ */
#define hashpointer(t,p) (gnode(t, (IntPoint(p) % ((sizenode(t)-1)|1)))) #define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
#define hashpointer(t,p) hashmod(t, IntPoint(p))
/*
** number of ints inside a lua_Number
*/
#define numints cast(int, sizeof(lua_Number)/sizeof(int))
/*
** hash for lua_Numbers
*/
static Node *hashnum (const Table *t, lua_Number n) {
unsigned int a[numints];
int i;
n += 1; /* normalize number (avoid -0) */
lua_assert(sizeof(a) <= sizeof(n));
memcpy(a, &n, sizeof(a));
for (i = 1; i < numints; i++) a[0] += a[i];
return hashmod(t, cast(lu_hash, a[0]));
}
/* /*
@ -73,11 +98,8 @@
*/ */
Node *luaH_mainposition (const Table *t, const TObject *key) { Node *luaH_mainposition (const Table *t, const TObject *key) {
switch (ttype(key)) { switch (ttype(key)) {
case LUA_TNUMBER: { case LUA_TNUMBER:
int ikey; return hashnum(t, nvalue(key));
lua_number2int(ikey, nvalue(key));
return hashnum(t, ikey);
}
case LUA_TSTRING: case LUA_TSTRING:
return hashstr(t, tsvalue(key)); return hashstr(t, tsvalue(key));
case LUA_TBOOLEAN: case LUA_TBOOLEAN:
@ -416,9 +438,10 @@ const TObject *luaH_getnum (Table *t, int key) {
if (1 <= key && key <= t->sizearray) if (1 <= key && key <= t->sizearray)
return &t->array[key-1]; return &t->array[key-1];
else { else {
Node *n = hashnum(t, key); lua_Number nk = cast(lua_Number, key);
Node *n = hashnum(t, nk);
do { /* check whether `key' is somewhere in the chain */ do { /* check whether `key' is somewhere in the chain */
if (ttisnumber(gkey(n)) && nvalue(gkey(n)) == (lua_Number)key) if (ttisnumber(gkey(n)) && nvalue(gkey(n)) == nk)
return gval(n); /* that's it */ return gval(n); /* that's it */
else n = n->next; else n = n->next;
} while (n); } while (n);