2 * This file is part of the GROMACS molecular simulation package.
4 * Copyright (c) 2012, by the GROMACS development team, led by
5 * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
6 * and including many others, as listed in the AUTHORS file in the
7 * top-level source directory and at http://www.gromacs.org.
9 * GROMACS is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public License
11 * as published by the Free Software Foundation; either version 2.1
12 * of the License, or (at your option) any later version.
14 * GROMACS is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with GROMACS; if not, see
21 * http://www.gnu.org/licenses, or write to the Free Software Foundation,
22 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
24 * If you want to redistribute modifications to GROMACS, please
25 * consider that scientific software is very special. Version
26 * control is crucial - bugs must be traceable. We will be happy to
27 * consider code for inclusion in the official distribution, but
28 * derived work must not be called official GROMACS. Details are found
29 * in the README & COPYING files - if they are missing, get the
30 * official version at http://www.gromacs.org.
32 * To help us fund GROMACS development, we humbly ask that you cite
33 * the research papers on the package. Check out http://www.gromacs.org.
45 /* This include file implements the simplest hash table possible.
46 * It is limited to integer keys and integer values.
47 * The purpose is highest efficiency and lowest memory usage possible.
49 * The type definition is placed in types/commrec.h, as it is used there:
50 * typedef struct gmx_hash *gmx_hash_t
59 typedef struct gmx_hash {
66 int start_space_search;
69 /* Clear all the entries in the hash table */
70 static void gmx_hash_clear(gmx_hash_t hash)
74 for (i = 0; i < hash->nalloc; i++)
76 hash->hash[i].key = -1;
77 hash->hash[i].next = -1;
79 hash->start_space_search = hash->mod;
84 static void gmx_hash_realloc(gmx_hash_t hash, int nkey_used_estimate)
86 /* Memory requirements:
87 * nkey_used_est*(2+1-2(1-e^-1/2))*3 ints
88 * where nkey_used_est is the local number of keys used.
90 * Make the direct list twice as long as the number of local keys.
91 * The fraction of entries in the list with:
93 * >=1 size lists: 1 - e^-f
94 * where f is: the #keys / mod
95 * The fraction of keys not in the direct list is: 1-1/f(1-e^-f).
96 * The optimal table size is roughly double the number of keys.
98 /* Make the hash table a power of 2 and at least double the number of keys */
100 while (2*nkey_used_estimate > hash->mod)
104 hash->mask = hash->mod - 1;
105 hash->nalloc = over_alloc_dd(hash->mod);
106 srenew(hash->hash, hash->nalloc);
110 fprintf(debug, "Hash table mod %d nalloc %d\n", hash->mod, hash->nalloc);
114 /* Clear all the entries in the hash table.
115 * With the current number of keys check if the table size is still good,
116 * if not optimize it with the currenr number of keys.
118 static void gmx_hash_clear_and_optimize(gmx_hash_t hash)
120 /* Resize the hash table when the occupation is < 1/4 or > 2/3 */
121 if (hash->nkey > 0 &&
122 (4*hash->nkey < hash->mod || 3*hash->nkey > 2*hash->mod))
126 fprintf(debug, "Hash table size %d #key %d: resizing\n",
127 hash->mod, hash->nkey);
129 gmx_hash_realloc(hash, hash->nkey);
132 gmx_hash_clear(hash);
135 static gmx_hash_t gmx_hash_init(int nkey_used_estimate)
142 gmx_hash_realloc(hash, nkey_used_estimate);
144 gmx_hash_clear(hash);
149 /* Set the hash entry for global atom a_gl to local atom a_loc and cell. */
150 static void gmx_hash_set(gmx_hash_t hash, int key, int value)
152 int ind, ind_prev, i;
154 ind = key & hash->mask;
156 if (hash->hash[ind].key >= 0)
158 /* Search the last entry in the linked list for this index */
160 while (hash->hash[ind_prev].next >= 0)
162 ind_prev = hash->hash[ind_prev].next;
164 /* Search for space in the array */
165 ind = hash->start_space_search;
166 while (ind < hash->nalloc && hash->hash[ind].key >= 0)
170 /* If we are at the end of the list we need to increase the size */
171 if (ind == hash->nalloc)
173 hash->nalloc = over_alloc_dd(ind+1);
174 srenew(hash->hash, hash->nalloc);
175 for (i = ind; i < hash->nalloc; i++)
177 hash->hash[i].key = -1;
178 hash->hash[i].next = -1;
181 hash->hash[ind_prev].next = ind;
183 hash->start_space_search = ind + 1;
185 hash->hash[ind].key = key;
186 hash->hash[ind].val = value;
191 /* Delete the hash entry for key */
192 static void gmx_hash_del(gmx_hash_t hash, int key)
197 ind = key & hash->mask;
200 if (hash->hash[ind].key == key)
204 hash->hash[ind_prev].next = hash->hash[ind].next;
206 /* This index is a linked entry, so we free an entry.
207 * Check if we are creating the first empty space.
209 if (ind < hash->start_space_search)
211 hash->start_space_search = ind;
214 hash->hash[ind].key = -1;
215 hash->hash[ind].val = -1;
216 hash->hash[ind].next = -1;
223 ind = hash->hash[ind].next;
230 /* Change the value for present hash entry for key */
231 static void gmx_hash_change_value(gmx_hash_t hash, int key, int value)
235 ind = key & hash->mask;
238 if (hash->hash[ind].key == key)
240 hash->hash[ind].val = value;
244 ind = hash->hash[ind].next;
251 /* Change the hash value if already set, otherwise set the hash value */
252 static void gmx_hash_change_or_set(gmx_hash_t hash, int key, int value)
256 ind = key & hash->mask;
259 if (hash->hash[ind].key == key)
261 hash->hash[ind].val = value;
265 ind = hash->hash[ind].next;
269 gmx_hash_set(hash, key, value);
274 /* Returns if the key is present, if the key is present *value is set */
275 static gmx_bool gmx_hash_get(const gmx_hash_t hash, int key, int *value)
279 ind = key & hash->mask;
282 if (hash->hash[ind].key == key)
284 *value = hash->hash[ind].val;
288 ind = hash->hash[ind].next;
295 /* Returns the value or -1 if the key is not present */
296 static int gmx_hash_get_minone(const gmx_hash_t hash, int key)
300 ind = key & hash->mask;
303 if (hash->hash[ind].key == key)
305 return hash->hash[ind].val;
307 ind = hash->hash[ind].next;
318 #endif /* _gmx_hash_h */