- replaced the hash table size heuristic with a table of hard coded table sizes
(taken from the GNU ISO C++ Library), which are all prime - replaced the string hash function by one that works slightly better & faster - changed various types to unsigned - added code to help debug the number of hash collisions (off by default) svn-id: r21431
This commit is contained in:
Max Horn
parent
7307c4cb3d
commit
9dc07c11cd
2 changed files with 92 additions and 61 deletions
|
|
@ -60,57 +60,68 @@
|
|||
namespace Common {
|
||||
|
||||
// int:
|
||||
int hashit(int x, int hashsize) {
|
||||
uint hashit(int x, uint hashsize) {
|
||||
return x % hashsize;
|
||||
}
|
||||
|
||||
int data_eq(int x, int y) {
|
||||
bool data_eq(int x, int y) {
|
||||
return x == y;
|
||||
}
|
||||
|
||||
#if 0
|
||||
// double:
|
||||
int hashit(double d, int hashsize) {
|
||||
int hash, dex;
|
||||
byte *p = (byte *)&d;
|
||||
|
||||
hash = 0;
|
||||
|
||||
for (dex = 0; dex < sizeof(double); dex++)
|
||||
hash = ((hash << 8) + p[dex]) % hashsize;
|
||||
|
||||
return hash;
|
||||
uint hashit(double d, uint hashsize) {
|
||||
TODO
|
||||
}
|
||||
#endif
|
||||
|
||||
int data_eq(double d1, double d2) {
|
||||
bool data_eq(double d1, double d2) {
|
||||
return (d1 == d2);
|
||||
}
|
||||
|
||||
// const char *:
|
||||
int hashit(const char *str, int hashsize) {
|
||||
uint hashit(const char *str, uint hashsize) {
|
||||
const byte *p = (const byte *)str;
|
||||
int hash, dex;
|
||||
uint hash;
|
||||
char c;
|
||||
|
||||
// my31 algo
|
||||
hash = 0;
|
||||
while ((c = *p++))
|
||||
hash = (hash * 31 + c);
|
||||
|
||||
for (dex = 0; p[dex] != 0; dex++)
|
||||
hash = ((hash << 8) + p[dex]) % hashsize;
|
||||
|
||||
return hash;
|
||||
return hash % hashsize;
|
||||
}
|
||||
|
||||
int data_eq(const char *str1, const char *str2) {
|
||||
bool data_eq(const char *str1, const char *str2) {
|
||||
return !strcmp(str1, str2);
|
||||
}
|
||||
|
||||
// String:
|
||||
int hashit(const Common::String &str, int hashsize) {
|
||||
uint hashit(const Common::String &str, uint hashsize) {
|
||||
return hashit(str.c_str(), hashsize);
|
||||
}
|
||||
|
||||
int data_eq(const Common::String &str1, const String &str2) {
|
||||
bool data_eq(const Common::String &str1, const String &str2) {
|
||||
return (str1 == str2);
|
||||
}
|
||||
|
||||
// The following table is taken from the GNU ISO C++ Library's hashtable.h file.
|
||||
static const uint primes[] = {
|
||||
53ul, 97ul, 193ul, 389ul, 769ul,
|
||||
1543ul, 3079ul, 6151ul, 12289ul, 24593ul,
|
||||
49157ul, 98317ul, 196613ul, 393241ul, 786433ul,
|
||||
1572869ul, 3145739ul, 6291469ul, 12582917ul, 25165843ul,
|
||||
50331653ul, 100663319ul, 201326611ul, 402653189ul, 805306457ul,
|
||||
1610612741ul, 3221225473ul, 4294967291ul
|
||||
};
|
||||
|
||||
uint nextTableSize(uint x) {
|
||||
int i = 0;
|
||||
while (x >= primes[i])
|
||||
i++;
|
||||
return primes[i];
|
||||
}
|
||||
|
||||
|
||||
} // End of namespace Common
|
||||
|
|
|
|||
|
|
@ -64,8 +64,6 @@
|
|||
|
||||
namespace Common {
|
||||
|
||||
#define INIT_SIZE 11
|
||||
|
||||
typedef Common::String String;
|
||||
|
||||
// If aa is an AssocArray<Key,Val>, then space is allocated each
|
||||
|
|
@ -80,14 +78,25 @@ typedef Common::String String;
|
|||
// be considered equal. Also, we assume that "=" works
|
||||
// on Val's for assignment.
|
||||
|
||||
int hashit(int x, int hashsize);
|
||||
int data_eq(int x, int y);
|
||||
int hashit(double x, int hashsize);
|
||||
int data_eq(double x, double y);
|
||||
int hashit(const char *str, int hashsize);
|
||||
int data_eq(const char *str1, const char *str2);
|
||||
int hashit(const String &str, int hashsize);
|
||||
int data_eq(const String &str1, const String &str2);
|
||||
uint hashit(int x, uint hashsize);
|
||||
bool data_eq(int x, int y);
|
||||
uint hashit(double x, uint hashsize);
|
||||
bool data_eq(double x, double y);
|
||||
uint hashit(const char *str, uint hashsize);
|
||||
bool data_eq(const char *str1, const char *str2);
|
||||
uint hashit(const String &str, uint hashsize);
|
||||
bool data_eq(const String &str1, const String &str2);
|
||||
|
||||
|
||||
// The table sizes ideally are primes. We use a helper function to find
|
||||
// suitable table sizes.
|
||||
uint nextTableSize(uint x);
|
||||
|
||||
|
||||
// Enable the following #define if you want to check how many collisions the
|
||||
// code produces (many collisions indicate either a bad hash function, or a
|
||||
// hash table that is too small).
|
||||
//#define DEBUG_HASH_COLLISIONS
|
||||
|
||||
template <class Key, class Val>
|
||||
class AssocArray {
|
||||
|
|
@ -101,7 +110,11 @@ private:
|
|||
};
|
||||
|
||||
aa_ref_t **_arr; // hashtable of size arrsize.
|
||||
int _arrsize, _nele;
|
||||
uint _arrsize, _nele;
|
||||
|
||||
#ifdef DEBUG_HASH_COLLISIONS
|
||||
mutable int _collisions;
|
||||
#endif
|
||||
|
||||
int lookup(const Key &key) const;
|
||||
void expand_array(void);
|
||||
|
|
@ -137,9 +150,7 @@ public:
|
|||
|
||||
template <class Key, class Val>
|
||||
int AssocArray<Key, Val>::lookup(const Key &key) const {
|
||||
int ctr;
|
||||
|
||||
ctr = hashit(key, _arrsize);
|
||||
uint ctr = hashit(key, _arrsize);
|
||||
|
||||
while (_arr[ctr] != NULL && !data_eq(_arr[ctr]->key, key)) {
|
||||
ctr++;
|
||||
|
|
@ -148,19 +159,23 @@ int AssocArray<Key, Val>::lookup(const Key &key) const {
|
|||
ctr = 0;
|
||||
}
|
||||
|
||||
#ifdef DEBUG_HASH_COLLISIONS
|
||||
fprintf(stderr, "collisions = %d in AssocArray %p\n", _collisions, (const void *)this);
|
||||
#endif
|
||||
|
||||
return ctr;
|
||||
}
|
||||
|
||||
template <class Key, class Val>
|
||||
bool AssocArray<Key, Val>::contains(const Key &key) const {
|
||||
int ctr = lookup(key);
|
||||
uint ctr = lookup(key);
|
||||
return (_arr[ctr] != NULL);
|
||||
}
|
||||
|
||||
template <class Key, class Val>
|
||||
Key *AssocArray<Key, Val>::new_all_keys(void) const {
|
||||
Key *all_keys;
|
||||
int ctr, dex;
|
||||
uint ctr, dex;
|
||||
|
||||
if (_nele == 0)
|
||||
return NULL;
|
||||
|
|
@ -186,7 +201,7 @@ Key *AssocArray<Key, Val>::new_all_keys(void) const {
|
|||
template <class Key, class Val>
|
||||
Val *AssocArray<Key, Val>::new_all_values(void) const {
|
||||
Val *all_values;
|
||||
int ctr, dex;
|
||||
uint ctr, dex;
|
||||
|
||||
if (_nele == 0)
|
||||
return NULL;
|
||||
|
|
@ -212,21 +227,24 @@ Val *AssocArray<Key, Val>::new_all_values(void) const {
|
|||
|
||||
template <class Key, class Val>
|
||||
AssocArray<Key, Val>::AssocArray() {
|
||||
int ctr;
|
||||
uint ctr;
|
||||
|
||||
_arr = new aa_ref_t *[INIT_SIZE];
|
||||
_arrsize = nextTableSize(0);
|
||||
_arr = new aa_ref_t *[_arrsize];
|
||||
assert(_arr != NULL);
|
||||
|
||||
for (ctr = 0; ctr < INIT_SIZE; ctr++)
|
||||
for (ctr = 0; ctr < _arrsize; ctr++)
|
||||
_arr[ctr] = NULL;
|
||||
|
||||
_arrsize = INIT_SIZE;
|
||||
_nele = 0;
|
||||
|
||||
#ifdef DEBUG_HASH_COLLISIONS
|
||||
_collisions = 0;
|
||||
#endif
|
||||
}
|
||||
|
||||
template <class Key, class Val>
|
||||
AssocArray<Key, Val>::~AssocArray() {
|
||||
int ctr;
|
||||
uint ctr;
|
||||
|
||||
for (ctr = 0; ctr < _arrsize; ctr++)
|
||||
if (_arr[ctr] != NULL)
|
||||
|
|
@ -237,20 +255,20 @@ AssocArray<Key, Val>::~AssocArray() {
|
|||
|
||||
template <class Key, class Val>
|
||||
void AssocArray<Key, Val>::clear(bool shrinkArray) {
|
||||
for (int ctr = 0; ctr < _arrsize; ctr++) {
|
||||
for (uint ctr = 0; ctr < _arrsize; ctr++) {
|
||||
if (_arr[ctr] != NULL) {
|
||||
delete _arr[ctr];
|
||||
_arr[ctr] = NULL;
|
||||
}
|
||||
}
|
||||
|
||||
if (shrinkArray && _arrsize > INIT_SIZE) {
|
||||
delete _arr;
|
||||
if (shrinkArray && _arrsize > nextTableSize(0)) {
|
||||
delete[] _arr;
|
||||
|
||||
_arr = new aa_ref_t *[INIT_SIZE];
|
||||
_arrsize = INIT_SIZE;
|
||||
|
||||
for (int ctr = 0; ctr < _arrsize; ctr++)
|
||||
_arrsize = nextTableSize(0);
|
||||
_arr = new aa_ref_t *[_arrsize];
|
||||
assert(_arr != NULL);
|
||||
for (uint ctr = 0; ctr < _arrsize; ctr++)
|
||||
_arr[ctr] = NULL;
|
||||
}
|
||||
|
||||
|
|
@ -260,19 +278,14 @@ void AssocArray<Key, Val>::clear(bool shrinkArray) {
|
|||
template <class Key, class Val>
|
||||
void AssocArray<Key, Val>::expand_array(void) {
|
||||
aa_ref_t **old_arr;
|
||||
int old_arrsize, old_nele, ctr, dex;
|
||||
uint old_arrsize, old_nele, ctr, dex;
|
||||
|
||||
old_nele = _nele;
|
||||
old_arr = _arr;
|
||||
old_arrsize = _arrsize;
|
||||
|
||||
// GROWTH_FACTOR 1.531415936535
|
||||
// allocate a new array
|
||||
_arrsize = 153 * old_arrsize / 100;
|
||||
|
||||
// Ensure that _arrsize is odd.
|
||||
_arrsize |= 1;
|
||||
|
||||
_arrsize = nextTableSize(old_arrsize);
|
||||
_arr = new aa_ref_t *[_arrsize];
|
||||
|
||||
assert(_arr != NULL);
|
||||
|
|
@ -307,12 +320,19 @@ void AssocArray<Key, Val>::expand_array(void) {
|
|||
|
||||
template <class Key, class Val>
|
||||
Val &AssocArray<Key, Val>::operator [](const Key &key) {
|
||||
int ctr = lookup(key);
|
||||
uint ctr = lookup(key);
|
||||
|
||||
if (_arr[ctr] == NULL) {
|
||||
_arr[ctr] = new aa_ref_t(key);
|
||||
_nele++;
|
||||
|
||||
#ifdef DEBUG_HASH_COLLISIONS
|
||||
if (ctr != hashit(key, _arrsize)) {
|
||||
_collisions++;
|
||||
// fprintf(stderr, "collisions = %d\n", _collisions);
|
||||
}
|
||||
#endif
|
||||
// Only fill array to fifty percent
|
||||
if (_nele > _arrsize / 2) {
|
||||
expand_array();
|
||||
ctr = lookup(key);
|
||||
|
|
@ -329,7 +349,7 @@ const Val &AssocArray<Key, Val>::operator [](const Key &key) const {
|
|||
|
||||
template <class Key, class Val>
|
||||
const Val &AssocArray<Key, Val>::queryVal(const Key &key) const {
|
||||
int ctr = lookup(key);
|
||||
uint ctr = lookup(key);
|
||||
assert(_arr[ctr] != NULL);
|
||||
return _arr[ctr]->dat;
|
||||
}
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue