summaryrefslogtreecommitdiff
path: root/src/pathfinder/npf/aystar.cpp
blob: addfc4930e34c02d70fb6d045775b447030039cd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file aystar.cpp Implementation of A*.
 *
 * This file has the core function for %AyStar.
 * %AyStar is a fast path finding routine and is used for things like AI path finding and Train path finding.
 * For more information about %AyStar (A* Algorithm), you can look at
 * <A HREF='http://en.wikipedia.org/wiki/A-star_search_algorithm'>http://en.wikipedia.org/wiki/A-star_search_algorithm</A>.
 */

/*
 * Friendly reminder:
 *  Call (AyStar).free() when you are done with Aystar. It reserves a lot of memory
 *  And when not free'd, it can cause system-crashes.
 * Also remember that when you stop an algorithm before it is finished, your
 * should call clear() yourself!
 */

#include "../../stdafx.h"
#include "../../core/alloc_func.hpp"
#include "aystar.h"

#include "../../safeguards.h"

/**
 * This looks in the hash whether a node exists in the closed list.
 * @param node Node to search.
 * @return The #PathNode if it is available, else \c nullptr
 */
PathNode *AyStar::ClosedListIsInList(const AyStarNode *node)
{
	return (PathNode*)this->closedlist_hash.Get(node->tile, node->direction);
}

/**
 * This adds a node to the closed list.
 * It makes a copy of the data.
 * @param node Node to add to the closed list.
 */
void AyStar::ClosedListAdd(const PathNode *node)
{
	/* Add a node to the ClosedList */
	PathNode *new_node = MallocT<PathNode>(1);
	*new_node = *node;
	this->closedlist_hash.Set(node->node.tile, node->node.direction, new_node);
}

/**
 * Check whether a node is in the open list.
 * @param node Node to search.
 * @return If the node is available, it is returned, else \c nullptr is returned.
 */
OpenListNode *AyStar::OpenListIsInList(const AyStarNode *node)
{
	return (OpenListNode*)this->openlist_hash.Get(node->tile, node->direction);
}

/**
 * Gets the best node from the open list.
 * It deletes the returned node from the open list.
 * @returns the best node available, or \c nullptr of none is found.
 */
OpenListNode *AyStar::OpenListPop()
{
	/* Return the item the Queue returns.. the best next OpenList item. */
	OpenListNode *res = (OpenListNode*)this->openlist_queue.Pop();
	if (res != nullptr) {
		this->openlist_hash.DeleteValue(res->path.node.tile, res->path.node.direction);
	}

	return res;
}

/**
 * Adds a node to the open list.
 * It makes a copy of node, and puts the pointer of parent in the struct.
 */
void AyStar::OpenListAdd(PathNode *parent, const AyStarNode *node, int f, int g)
{
	/* Add a new Node to the OpenList */
	OpenListNode *new_node = MallocT<OpenListNode>(1);
	new_node->g = g;
	new_node->path.parent = parent;
	new_node->path.node = *node;
	this->openlist_hash.Set(node->tile, node->direction, new_node);

	/* Add it to the queue */
	this->openlist_queue.Push(new_node, f);
}

/**
 * Checks one tile and calculate its f-value
 */
void AyStar::CheckTile(AyStarNode *current, OpenListNode *parent)
{
	int new_f, new_g, new_h;
	PathNode *closedlist_parent;
	OpenListNode *check;

	/* Check the new node against the ClosedList */
	if (this->ClosedListIsInList(current) != nullptr) return;

	/* Calculate the G-value for this node */
	new_g = this->CalculateG(this, current, parent);
	/* If the value was INVALID_NODE, we don't do anything with this node */
	if (new_g == AYSTAR_INVALID_NODE) return;

	/* There should not be given any other error-code.. */
	assert(new_g >= 0);
	/* Add the parent g-value to the new g-value */
	new_g += parent->g;
	if (this->max_path_cost != 0 && (uint)new_g > this->max_path_cost) return;

	/* Calculate the h-value */
	new_h = this->CalculateH(this, current, parent);
	/* There should not be given any error-code.. */
	assert(new_h >= 0);

	/* The f-value if g + h */
	new_f = new_g + new_h;

	/* Get the pointer to the parent in the ClosedList (the current one is to a copy of the one in the OpenList) */
	closedlist_parent = this->ClosedListIsInList(&parent->path.node);

	/* Check if this item is already in the OpenList */
	check = this->OpenListIsInList(current);
	if (check != nullptr) {
		uint i;
		/* Yes, check if this g value is lower.. */
		if (new_g > check->g) return;
		this->openlist_queue.Delete(check, 0);
		/* It is lower, so change it to this item */
		check->g = new_g;
		check->path.parent = closedlist_parent;
		/* Copy user data, will probably have changed */
		for (i = 0; i < lengthof(current->user_data); i++) {
			check->path.node.user_data[i] = current->user_data[i];
		}
		/* Re-add it in the openlist_queue. */
		this->openlist_queue.Push(check, new_f);
	} else {
		/* A new node, add him to the OpenList */
		this->OpenListAdd(closedlist_parent, current, new_f, new_g);
	}
}

/**
 * This function is the core of %AyStar. It handles one item and checks
 * his neighbour items. If they are valid, they are added to be checked too.
 * @return Possible values:
 *  - #AYSTAR_EMPTY_OPENLIST : indicates all items are tested, and no path has been found.
 *  - #AYSTAR_LIMIT_REACHED : Indicates that the max_search_nodes limit has been reached.
 *  - #AYSTAR_FOUND_END_NODE : indicates we found the end. Path_found now is true, and in path is the path found.
 *  - #AYSTAR_STILL_BUSY : indicates we have done this tile, did not found the path yet, and have items left to try.
 */
int AyStar::Loop()
{
	int i;

	/* Get the best node from OpenList */
	OpenListNode *current = this->OpenListPop();
	/* If empty, drop an error */
	if (current == nullptr) return AYSTAR_EMPTY_OPENLIST;

	/* Check for end node and if found, return that code */
	if (this->EndNodeCheck(this, current) == AYSTAR_FOUND_END_NODE && !CheckIgnoreFirstTile(&current->path)) {
		if (this->FoundEndNode != nullptr) {
			this->FoundEndNode(this, current);
		}
		free(current);
		return AYSTAR_FOUND_END_NODE;
	}

	/* Add the node to the ClosedList */
	this->ClosedListAdd(&current->path);

	/* Load the neighbours */
	this->GetNeighbours(this, current);

	/* Go through all neighbours */
	for (i = 0; i < this->num_neighbours; i++) {
		/* Check and add them to the OpenList if needed */
		this->CheckTile(&this->neighbours[i], current);
	}

	/* Free the node */
	free(current);

	if (this->max_search_nodes != 0 && this->closedlist_hash.GetSize() >= this->max_search_nodes) {
		/* We've expanded enough nodes */
		return AYSTAR_LIMIT_REACHED;
	} else {
		/* Return that we are still busy */
		return AYSTAR_STILL_BUSY;
	}
}

/**
 * This function frees the memory it allocated
 */
void AyStar::Free()
{
	this->openlist_queue.Free(false);
	/* 2nd argument above is false, below is true, to free the values only
	 * once */
	this->openlist_hash.Delete(true);
	this->closedlist_hash.Delete(true);
#ifdef AYSTAR_DEBUG
	printf("[AyStar] Memory free'd\n");
#endif
}

/**
 * This function make the memory go back to zero.
 * This function should be called when you are using the same instance again.
 */
void AyStar::Clear()
{
	/* Clean the Queue, but not the elements within. That will be done by
	 * the hash. */
	this->openlist_queue.Clear(false);
	/* Clean the hashes */
	this->openlist_hash.Clear(true);
	this->closedlist_hash.Clear(true);

#ifdef AYSTAR_DEBUG
	printf("[AyStar] Cleared AyStar\n");
#endif
}

/**
 * This is the function you call to run AyStar.
 * @return Possible values:
 *  - #AYSTAR_FOUND_END_NODE : indicates we found an end node.
 *  - #AYSTAR_NO_PATH : indicates that there was no path found.
 *  - #AYSTAR_STILL_BUSY : indicates we have done some checked, that we did not found the path yet, and that we still have items left to try.
 * @note When the algorithm is done (when the return value is not #AYSTAR_STILL_BUSY) #Clear() is called automatically.
 *       When you stop the algorithm halfway, you should call #Clear() yourself!
 */
int AyStar::Main()
{
	int r, i = 0;
	/* Loop through the OpenList
	 *  Quit if result is no AYSTAR_STILL_BUSY or is more than loops_per_tick */
	while ((r = this->Loop()) == AYSTAR_STILL_BUSY && (this->loops_per_tick == 0 || ++i < this->loops_per_tick)) { }
#ifdef AYSTAR_DEBUG
	switch (r) {
		case AYSTAR_FOUND_END_NODE: printf("[AyStar] Found path!\n"); break;
		case AYSTAR_EMPTY_OPENLIST: printf("[AyStar] OpenList run dry, no path found\n"); break;
		case AYSTAR_LIMIT_REACHED:  printf("[AyStar] Exceeded search_nodes, no path found\n"); break;
		default: break;
	}
#endif
	if (r != AYSTAR_STILL_BUSY) {
		/* We're done, clean up */
		this->Clear();
	}

	switch (r) {
		case AYSTAR_FOUND_END_NODE: return AYSTAR_FOUND_END_NODE;
		case AYSTAR_EMPTY_OPENLIST:
		case AYSTAR_LIMIT_REACHED:  return AYSTAR_NO_PATH;
		default:                    return AYSTAR_STILL_BUSY;
	}
}

/**
 * Adds a node from where to start an algorithm. Multiple nodes can be added
 * if wanted. You should make sure that #Clear() is called before adding nodes
 * if the #AyStar has been used before (though the normal main loop calls
 * #Clear() automatically when the algorithm finishes.
 * @param start_node Node to start with.
 * @param g the cost for starting with this node.
 */
void AyStar::AddStartNode(AyStarNode *start_node, uint g)
{
#ifdef AYSTAR_DEBUG
	printf("[AyStar] Starting A* Algorithm from node (%d, %d, %d)\n",
		TileX(start_node->tile), TileY(start_node->tile), start_node->direction);
#endif
	this->OpenListAdd(nullptr, start_node, 0, g);
}

/**
 * Initialize an #AyStar. You should fill all appropriate fields before
 * calling #Init (see the declaration of #AyStar for which fields are internal).
 */
void AyStar::Init(Hash_HashProc hash, uint num_buckets)
{
	/* Allocated the Hash for the OpenList and ClosedList */
	this->openlist_hash.Init(hash, num_buckets);
	this->closedlist_hash.Init(hash, num_buckets);

	/* Set up our sorting queue
	 *  BinaryHeap allocates a block of 1024 nodes
	 *  When that one gets full it reserves another one, till this number
	 *  That is why it can stay this high */
	this->openlist_queue.Init(102400);
}