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Alteracao do hash, trocando tratamento de colisao por lista 

pela estrategia de re-hash.
Foi feito uma avaliacao da funcao de hash, e constatado sua
eficiencia com uma media de 4 acessos no hash ate' 70% ocupado.
This commit is contained in:
Waldemar Celes 1994-08-09 08:24:45 -03:00
parent 41fd23287a
commit b28da81cfe
2 changed files with 156 additions and 162 deletions
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312
hash.c
View File

@ -1,10 +1,9 @@
/* /*
** hash.c ** hash.c
** hash manager for lua ** hash manager for lua
** Luiz Henrique de Figueiredo - 17 Aug 90
*/ */
char *rcs_hash="$Id: hash.c,v 2.2 1994/07/19 21:27:18 celes Exp celes $"; char *rcs_hash="$Id: hash.c,v 2.3 1994/08/05 19:25:09 celes Exp celes $";
#include <string.h> #include <string.h>
#include <stdlib.h> #include <stdlib.h>
@ -17,19 +16,21 @@ char *rcs_hash="$Id: hash.c,v 2.2 1994/07/19 21:27:18 celes Exp celes $";
#include "table.h" #include "table.h"
#include "lua.h" #include "lua.h"
#define streq(s1,s2) (strcmp(s1,s2)==0) #define streq(s1,s2) (*(s1) == *(s2) && strcmp(s1,s2)==0)
#define strneq(s1,s2) (strcmp(s1,s2)!=0)
#define new(s) ((s *)malloc(sizeof(s))) #define new(s) ((s *)malloc(sizeof(s)))
#define newvector(n,s) ((s *)calloc(n,sizeof(s))) #define newvector(n,s) ((s *)calloc(n,sizeof(s)))
#define nhash(t) ((t)->nhash) #define nhash(t) ((t)->nhash)
#define nodelist(t) ((t)->list) #define nuse(t) ((t)->nuse)
#define list(t,i) ((t)->list[i])
#define markarray(t) ((t)->mark) #define markarray(t) ((t)->mark)
#define ref_tag(n) (tag(&(n)->ref)) #define nodevector(t) ((t)->node)
#define ref_nvalue(n) (nvalue(&(n)->ref)) #define node(t,i) (&(t)->node[i])
#define ref_svalue(n) (svalue(&(n)->ref)) #define ref(n) (&(n)->ref)
#define val(n) (&(n)->val)
#define REHASH_LIMIT 0.70 /* avoid more than this % full */
typedef struct ArrayList typedef struct ArrayList
@ -40,68 +41,97 @@ typedef struct ArrayList
static ArrayList *listhead = NULL; static ArrayList *listhead = NULL;
static int head (Hash *t, Object *ref) /* hash function */
/* hash dimensions values */
static int dimensions[] =
{7, 11, 23, 47, 97, 197, 397, 797, 1597, 3203, 6421, 12853, 25717, 51437, 0};
static int redimension (int nhash)
{ {
if (tag(ref) == T_NUMBER) return (((int)nvalue(ref))%nhash(t)); int i;
else if (tag(ref) == T_STRING) for (i=0; dimensions[i]!=0; i++)
{ {
int h; if (dimensions[i] > nhash)
char *name = svalue(ref); return dimensions[i];
for (h=0; *name!=0; name++) /* interpret name as binary number */ }
return nhash*2+1;
}
static int index (Hash *t, Object *ref) /* hash function */
{
switch (tag(ref))
{
case T_NUMBER:
return (((int)nvalue(ref))%nhash(t));
case T_STRING:
{ {
h <<= 8; int h;
h += (unsigned char) *name; /* avoid sign extension */ char *name = svalue(ref);
h %= nhash(t); /* make it a valid index */ for (h=0; *name!=0; name++) /* interpret name as binary number */
{
h <<= 8;
h += (unsigned char) *name; /* avoid sign extension */
h %= nhash(t); /* make it a valid index */
}
return h;
} }
return h; case T_FUNCTION:
} return (((int)bvalue(ref))%nhash(t));
else case T_CFUNCTION:
{ return (((int)fvalue(ref))%nhash(t));
lua_reportbug ("unexpected type to index table"); case T_ARRAY:
return -1; return (((int)avalue(ref))%nhash(t));
case T_USERDATA:
return (((int)uvalue(ref))%nhash(t));
default:
lua_reportbug ("unexpected type to index table");
return -1;
} }
} }
static Node *present(Hash *t, Object *ref, int h) static int present (Hash *t, Object *ref)
{
int h = index(t, ref);
if (h < 0) return h;
while (tag(ref(node(t, h))) != T_NIL)
{
NCOLISSIONS++;
if (tag(ref) == T_NUMBER && tag(ref(node(t, h))) == T_NUMBER &&
nvalue(ref) == nvalue(ref(node(t, h)))
) return h;
if (tag(ref) == T_STRING && tag(ref(node(t, h))) == T_STRING &&
streq(svalue(ref),svalue(ref(node(t, h))))
) return h;
if (tag(ref) == tag(ref(node(t, h))) &&
uvalue(ref) == uvalue(ref(node(t, h))) /* all others are pointers */
) return h;
h = (h+1) % nhash(t);
}
return h;
}
/*
** Alloc a vector node
*/
static Node *hashnodecreate (int nhash)
{ {
Node *n=NULL, *p; int i;
if (tag(ref) == T_NUMBER) Node *v = newvector (nhash, Node);
if (v == NULL)
{ {
for (p=NULL,n=list(t,h); n!=NULL; p=n, n=n->next) lua_error ("not enough memory");
if (ref_tag(n) == T_NUMBER && nvalue(ref) == ref_nvalue(n)) break;
}
else if (tag(ref) == T_STRING)
{
for (p=NULL,n=list(t,h); n!=NULL; p=n, n=n->next)
if (ref_tag(n) == T_STRING && streq(svalue(ref),ref_svalue(n))) break;
}
if (n==NULL) /* name not present */
return NULL; return NULL;
#if 0
if (p!=NULL) /* name present but not first */
{
p->next=n->next; /* move-to-front self-organization */
n->next=list(t,h);
list(t,h)=n;
}
#endif
return n;
}
static void freelist (Node *n)
{
while (n)
{
Node *next = n->next;
free (n);
n = next;
} }
for (i=0; i<nhash; i++)
tag(ref(&v[i])) = T_NIL;
return v;
} }
/* /*
** Create a new hash. Return the hash pointer or NULL on error. ** Create a new hash. Return the hash pointer or NULL on error.
*/ */
static Hash *hashcreate (unsigned int nhash) static Hash *hashcreate (int nhash)
{ {
Hash *t = new (Hash); Hash *t = new (Hash);
if (t == NULL) if (t == NULL)
@ -109,27 +139,25 @@ static Hash *hashcreate (unsigned int nhash)
lua_error ("not enough memory"); lua_error ("not enough memory");
return NULL; return NULL;
} }
nhash(t) = nhash; nhash = redimension(nhash);
markarray(t) = 0;
nodelist(t) = newvector (nhash, Node*); nodevector(t) = hashnodecreate(nhash);
if (nodelist(t) == NULL) if (nodevector(t) == NULL)
{
lua_error ("not enough memory");
return NULL; return NULL;
}
nhash(t) = nhash;
nuse(t) = 0;
markarray(t) = 0;
return t; return t;
} }
/* /*
** Delete a hash ** Delete a hash
*/ */
static void hashdelete (Hash *h) static void hashdelete (Hash *t)
{ {
int i; free (nodevector(t));
for (i=0; i<nhash(h); i++) free(t);
freelist (list(h,i));
free (nodelist(h));
free(h);
} }
@ -144,8 +172,8 @@ void lua_hashmark (Hash *h)
markarray(h) = 1; markarray(h) = 1;
for (i=0; i<nhash(h); i++) for (i=0; i<nhash(h); i++)
{ {
Node *n; Node *n = node(h,i);
for (n = list(h,i); n != NULL; n = n->next) if (tag(ref(n)) != T_NIL)
{ {
lua_markobject(&n->ref); lua_markobject(&n->ref);
lua_markobject(&n->val); lua_markobject(&n->val);
@ -212,6 +240,25 @@ Hash *lua_createarray (int nhash)
} }
/*
** Re-hash
*/
static void rehash (Hash *t)
{
int i;
int nold = nhash(t);
Node *vold = nodevector(t);
nhash(t) = redimension(nhash(t));
nodevector(t) = hashnodecreate(nhash(t));
for (i=0; i<nold; i++)
{
Node *n = vold+i;
if (tag(ref(n)) != T_NIL && tag(val(n)) != T_NIL)
*node(t, present(t, ref(n))) = *n; /* copy old node to new hahs */
}
free(vold);
}
/* /*
** If the hash node is present, return its pointer, otherwise return a ** If the hash node is present, return its pointer, otherwise return a
** static nil object ** static nil object
@ -219,12 +266,10 @@ Hash *lua_createarray (int nhash)
Object *lua_hashget (Hash *t, Object *ref) Object *lua_hashget (Hash *t, Object *ref)
{ {
static Object nil_obj = {T_NIL, {NULL}}; static Object nil_obj = {T_NIL, {NULL}};
Node *n; int h = present(t, ref);
int h = head (t, ref);
if (h < 0) return NULL; if (h < 0) return NULL;
n = present(t, ref, h); if (tag(ref(node(t, h))) == T_NIL) return &nil_obj;
if (n == NULL) return &nil_obj; else return val(node(t, h));
else return &n->val;
} }
/* /*
@ -236,24 +281,22 @@ Object *lua_hashdefine (Hash *t, Object *ref)
{ {
int h; int h;
Node *n; Node *n;
h = head (t, ref); h = present(t, ref);
if (h < 0) return NULL; if (h < 0) return NULL;
n = node(t, h);
n = present(t, ref, h); if (tag(ref(n)) == T_NIL)
if (n == NULL)
{ {
n = new(Node); nuse(t)++;
if (n == NULL) if (nuse(t) > nhash(t)*REHASH_LIMIT)
{ {
lua_error ("not enough memory"); rehash(t);
return NULL; h = present(t, ref);
n = node(t, h);
} }
n->ref = *ref; *ref(n) = *ref;
tag(&n->val) = T_NIL; tag(val(n)) = T_NIL;
n->next = list(t,h); /* link node to head of list */
list(t,h) = n;
} }
return (&n->val); return (val(n));
} }
@ -263,41 +306,28 @@ Object *lua_hashdefine (Hash *t, Object *ref)
** in the hash. ** in the hash.
** This function pushs the element value and its reference to the stack. ** This function pushs the element value and its reference to the stack.
*/ */
static void firstnode (Hash *a, int h) static void hashnext (Hash *t, int i)
{ {
if (h < nhash(a)) if (i >= nhash(t))
{ {
int i; lua_pushnil(); lua_pushnil();
for (i=h; i<nhash(a); i++) return;
}
while (tag(ref(node(t,i))) == T_NIL || tag(val(node(t,i))) == T_NIL)
{
if (++i >= nhash(t))
{ {
if (list(a,i) != NULL) lua_pushnil(); lua_pushnil();
{ return;
if (tag(&list(a,i)->val) != T_NIL)
{
lua_pushobject (&list(a,i)->ref);
lua_pushobject (&list(a,i)->val);
return;
}
else
{
Node *next = list(a,i)->next;
while (next != NULL && tag(&next->val) == T_NIL) next = next->next;
if (next != NULL)
{
lua_pushobject (&next->ref);
lua_pushobject (&next->val);
return;
}
}
}
} }
} }
lua_pushnil(); lua_pushobject(ref(node(t,i)));
lua_pushnil(); lua_pushobject(val(node(t,i)));
} }
void lua_next (void) void lua_next (void)
{ {
Hash *a; Hash *t;
Object *o = lua_getparam (1); Object *o = lua_getparam (1);
Object *r = lua_getparam (2); Object *r = lua_getparam (2);
if (o == NULL || r == NULL) if (o == NULL || r == NULL)
@ -306,55 +336,19 @@ void lua_next (void)
{ lua_error ("too many arguments to function `next'"); return; } { lua_error ("too many arguments to function `next'"); return; }
if (tag(o) != T_ARRAY) if (tag(o) != T_ARRAY)
{ lua_error ("first argument of function `next' is not a table"); return; } { lua_error ("first argument of function `next' is not a table"); return; }
a = avalue(o);
t = avalue(o);
if (tag(r) == T_NIL) if (tag(r) == T_NIL)
{ {
firstnode (a, 0); hashnext(t, 0);
return;
} }
else else
{ {
int h = head (a, r); int h = present (t, r);
if (h >= 0) if (h >= 0)
{ hashnext(t, h+1);
Node *n = list(a,h); else
while (n) lua_error ("error in function 'next': reference not found");
{
if (memcmp(&n->ref,r,sizeof(Object)) == 0)
{
if (n->next == NULL)
{
firstnode (a, h+1);
return;
}
else if (tag(&n->next->val) != T_NIL)
{
lua_pushobject (&n->next->ref);
lua_pushobject (&n->next->val);
return;
}
else
{
Node *next = n->next->next;
while (next != NULL && tag(&next->val) == T_NIL) next = next->next;
if (next == NULL)
{
firstnode (a, h+1);
return;
}
else
{
lua_pushobject (&next->ref);
lua_pushobject (&next->val);
}
return;
}
}
n = n->next;
}
if (n == NULL)
lua_error ("error in function 'next': reference not found");
}
} }
} }

6
hash.h
View File

@ -2,7 +2,7 @@
** hash.h ** hash.h
** hash manager for lua ** hash manager for lua
** Luiz Henrique de Figueiredo - 17 Aug 90 ** Luiz Henrique de Figueiredo - 17 Aug 90
** $Id: hash.h,v 2.1 1994/04/20 22:07:57 celes Exp celes $ ** $Id: hash.h,v 2.2 1994/08/05 19:25:09 celes Exp celes $
*/ */
#ifndef hash_h #ifndef hash_h
@ -12,14 +12,14 @@ typedef struct node
{ {
Object ref; Object ref;
Object val; Object val;
struct node *next;
} Node; } Node;
typedef struct Hash typedef struct Hash
{ {
char mark; char mark;
unsigned int nhash; unsigned int nhash;
Node **list; unsigned int nuse;
Node *node;
} Hash; } Hash;