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small optimization

This commit is contained in:
Roberto Ierusalimschy 2002-01-16 20:02:46 -02:00
parent 6272c843de
commit 566310fa04
1 changed files with 13 additions and 8 deletions
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21
ltable.c
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@ -138,20 +138,22 @@ int luaH_nexti (Table *t, int i, TObject *where) {
static void computesizes (int nums[], int ntotal, int *narray, int *nhash) { static void computesizes (int nums[], int ntotal, int *narray, int *nhash) {
int n = 0; /* optimal (log of) size for array part */ int n = 0; /* (log of) optimal size for array part */
int na = 0; /* number of elements to go to array part */ int na = 0; /* number of elements to go to array part */
int a = nums[0]; /* accumulator */ int i=0;
int i; int a = nums[0]; /* number of elements smaller than 2^i */
for (i=1; i<=MAXBITS; i++) { while (++i <= MAXBITS && *narray >= twoto(i-1)) {
if (nums[i] == 0) continue; /* ignore empty slices */ if (nums[i] == 0) continue;
a += nums[i]; /* number of elements smaller than 2^i */ a += nums[i];
if (a >= (1<<(i-1))) { /* more than half elements in use? */ if (a >= twoto(i-1)) { /* more than half elements in use? */
n = i; n = i;
na = a; na = a;
} }
} }
lua_assert(na <= *narray && *narray <= ntotal);
*nhash = ntotal - na; *nhash = ntotal - na;
*narray = (n == 0) ? 0 : (1<<n); *narray = (n == 0) ? 0 : (1<<n);
lua_assert(na <= *narray && na >= *narray/2);
} }
@ -172,13 +174,16 @@ static void numuse (const Table *t, int *narray, int *nhash) {
totaluse++; totaluse++;
} }
} }
*narray = totaluse; /* all previous uses were in array part */
/* count elements in hash part */ /* count elements in hash part */
i = sizenode(t); i = sizenode(t);
while (i--) { while (i--) {
if (ttype(val(&t->node[i])) != LUA_TNIL) { if (ttype(val(&t->node[i])) != LUA_TNIL) {
int k = arrayindex(key(&t->node[i])); int k = arrayindex(key(&t->node[i]));
if (k >= 0) /* is `key' an appropriate array index? */ if (k >= 0) { /* is `key' an appropriate array index? */
nums[luaO_log2(k-1)+1]++; /* count as such */ nums[luaO_log2(k-1)+1]++; /* count as such */
(*narray)++;
}
totaluse++; totaluse++;
} }
} }