commit b858161fbcd3992e91c1e555ca7797ec8bec3f84
parent 80bac182db4bba6fc0dcfdb0d4d6abe4183083d1
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 24 Mar 2003 11:18:20 -0300
new hash method for lua_Number (double) (due to a performance problem)
Diffstat:
M | ltable.c | | | 53 | ++++++++++++++++++++++++++++++++++++++--------------- |
1 file changed, 38 insertions(+), 15 deletions(-)
diff --git a/ltable.c b/ltable.c
@@ -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)
** See Copyright Notice in lua.h
*/
@@ -21,6 +21,7 @@
** performance penalties.
*/
+#include <string.h>
#define ltable_c
@@ -54,17 +55,41 @@
#endif
-#define hashg(t,n) (gnode(t, lmod((n), sizenode(t))))
+#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
-#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)
+#define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
+#define hashboolean(t,p) hashpow2(t, p)
+
+
+/*
+** for some types, it is better to avoid modulus by power of 2, as
+** they tend to have many 2 factors.
+*/
+#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))
+
/*
-** avoid modulus by power of 2 for pointers, as they tend to have many
-** 2 factors.
+** hash for lua_Numbers
*/
-#define hashpointer(t,p) (gnode(t, (IntPoint(p) % ((sizenode(t)-1)|1))))
+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) {
switch (ttype(key)) {
- case LUA_TNUMBER: {
- int ikey;
- lua_number2int(ikey, nvalue(key));
- return hashnum(t, ikey);
- }
+ case LUA_TNUMBER:
+ return hashnum(t, nvalue(key));
case LUA_TSTRING:
return hashstr(t, tsvalue(key));
case LUA_TBOOLEAN:
@@ -416,9 +438,10 @@ const TObject *luaH_getnum (Table *t, int key) {
if (1 <= key && key <= t->sizearray)
return &t->array[key-1];
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 */
- if (ttisnumber(gkey(n)) && nvalue(gkey(n)) == (lua_Number)key)
+ if (ttisnumber(gkey(n)) && nvalue(gkey(n)) == nk)
return gval(n); /* that's it */
else n = n->next;
} while (n);