thirdparty/scummvm
2
0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Revised HashMap implementation

Browse source 
svn-id: r34273
This commit is contained in:
Max Horn 2008-09-02 11:34:12 +00:00
parent 155b8606c1
commit 31ce5eb496
4 changed files with 231 additions and 179 deletions
Download patch file Download diff file Expand all files Collapse all files

89
common/hashmap.cpp
View file

@ -24,69 +24,35 @@
*/
// The hash map (associative array) implementation in this file is
// based on code by Andrew Y. Ng, 1996:
/*
* Copyright (c) 1998-2003 Massachusetts Institute of Technology.
* This code was developed as part of the Haystack research project
* (http://haystack.lcs.mit.edu/). Permission is hereby granted,
* free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute,
* sublicense, and/or sell copies of the Software, and to permit
* persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
// based on the PyDict implementation of CPython. The erase() method
// is based on example code in the Wikipedia article on Hash tables.
#include "common/hashmap.h"
namespace Common {
// const char *:
// Hash function for strings, taken from CPython.
uint hashit(const char *p) {
uint hash = 0;
uint hash = *p << 7;
byte c;
while ((c = *p++))
hash = (hash * 31 + c);
return hash;
int size = 0;
while ((c = *p++)) {
hash = (1000003 * hash) ^ c;
size++;
}
return hash ^ size;
}
// Like hashit, but converts every char to lowercase before hashing.
uint hashit_lower(const char *p) {
uint hash = 0;
uint hash = tolower(*p) << 7;
byte c;
while ((c = *p++))
hash = (hash * 31 + tolower(c));
return hash;
}
// 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];
int size = 0;
while ((c = *p++)) {
hash = (1000003 * hash) ^ tolower(c);
size++;
}
return hash ^ size;
}
#ifdef DEBUG_HASH_COLLISIONS
@ -98,6 +64,7 @@ static double
g_size = 0;
static int g_max_capacity = 0, g_max_size = 0;
static int g_totalHashmaps = 0;
static int g_stats[4] = {0,0,0,0};
void updateHashCollisionStats(int collisions, int lookups, int arrsize, int nele) {
g_collisions += collisions;
@ -108,6 +75,15 @@ void updateHashCollisionStats(int collisions, int lookups, int arrsize, int nele
g_size += nele;
g_totalHashmaps++;
if (3*nele <= 2*8)
g_stats[0]++;
if (3*nele <= 2*16)
g_stats[1]++;
if (3*nele <= 2*32)
g_stats[2]++;
if (3*nele <= 2*64)
g_stats[3]++;
g_max_capacity = MAX(g_max_capacity, arrsize);
g_max_size = MAX(g_max_size, nele);
@ -118,6 +94,15 @@ void updateHashCollisionStats(int collisions, int lookups, int arrsize, int nele
100 * g_collPerLook / g_totalHashmaps,
g_size / g_totalHashmaps, g_max_size,
g_capacity / g_totalHashmaps, g_max_capacity);
fprintf(stdout, " %d less than %d; %d less than %d; %d less than %d; %d less than %d\n",
g_stats[0], 2*8/3,
g_stats[1],2*16/3,
g_stats[2],2*32/3,
g_stats[3],2*64/3);
// TODO:
// * Should record the maximal size of the map during its lifetime, not that at its death
// * Should do some statistics: how many maps are less than 2/3*8, 2/3*16, 2/3*32, ...
}
#endif