summaryrefslogtreecommitdiff
path: root/aystar.c
blob: 229da27b14e1c5ef071ca5f31047c5e69da79f2c (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
/* $Id$ */

/*
 * This file has the core function for AyStar
 *  AyStar is a fast pathfinding routine and is used for things like
 *  AI_pathfinding and Train_pathfinding.
 *  For more information about AyStar (A* Algorithm), you can look at
 *    http://en.wikipedia.org/wiki/A-star_search_algorithm
 */

/*
 * 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 "openttd.h"
#include "aystar.h"

int _aystar_stats_open_size;
int _aystar_stats_closed_size;

// This looks in the Hash if a node exists in ClosedList
//  If so, it returns the PathNode, else NULL
static PathNode *AyStarMain_ClosedList_IsInList(AyStar *aystar, AyStarNode *node)
{
	return (PathNode*)Hash_Get(&aystar->ClosedListHash, node->tile, node->direction);
}

// This adds a node to the ClosedList
//  It makes a copy of the data
static void AyStarMain_ClosedList_Add(AyStar *aystar, PathNode *node)
{
	// Add a node to the ClosedList
	PathNode *new_node = malloc(sizeof(PathNode));
	*new_node = *node;
	Hash_Set(&aystar->ClosedListHash, node->node.tile, node->node.direction, new_node);
}

// Checks if a node is in the OpenList
//   If so, it returns the OpenListNode, else NULL
static OpenListNode *AyStarMain_OpenList_IsInList(AyStar *aystar, AyStarNode *node)
{
	return (OpenListNode*)Hash_Get(&aystar->OpenListHash, node->tile, node->direction);
}

// Gets the best node from OpenList
//  returns the best node, or NULL of none is found
// Also it deletes the node from the OpenList
static OpenListNode *AyStarMain_OpenList_Pop(AyStar *aystar)
{
	// Return the item the Queue returns.. the best next OpenList item.
	OpenListNode* res = (OpenListNode*)aystar->OpenListQueue.pop(&aystar->OpenListQueue);
	if (res != NULL)
		Hash_Delete(&aystar->OpenListHash, res->path.node.tile, res->path.node.direction);

	return res;
}

// Adds a node to the OpenList
//  It makes a copy of node, and puts the pointer of parent in the struct
static void AyStarMain_OpenList_Add(AyStar *aystar, PathNode *parent, AyStarNode *node, int f, int g)
{
	// Add a new Node to the OpenList
	OpenListNode* new_node = malloc(sizeof(OpenListNode));
	new_node->g = g;
	new_node->path.parent = parent;
	new_node->path.node = *node;
	Hash_Set(&aystar->OpenListHash, node->tile, node->direction, new_node);

	// Add it to the queue
	aystar->OpenListQueue.push(&aystar->OpenListQueue, new_node, f);
}

/*
 * Checks one tile and calculate his f-value
 *  return values:
 *	AYSTAR_DONE : indicates we are done
 */
int AyStarMain_CheckTile(AyStar *aystar, AyStarNode *current, OpenListNode *parent) {
	int new_f, new_g, new_h;
	PathNode *closedlist_parent;
	OpenListNode *check;

	// Check the new node against the ClosedList
	if (AyStarMain_ClosedList_IsInList(aystar, current) != NULL) return AYSTAR_DONE;

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

	// 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 (aystar->max_path_cost != 0 && (uint)new_g > aystar->max_path_cost) return AYSTAR_DONE;

	// Calculate the h-value
	new_h = aystar->CalculateH(aystar, 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 currentone is to a copy of the one in the OpenList)
	closedlist_parent = AyStarMain_ClosedList_IsInList(aystar, &parent->path.node);

	// Check if this item is already in the OpenList
	if ((check = AyStarMain_OpenList_IsInList(aystar, current)) != NULL) {
		uint i;
		// Yes, check if this g value is lower..
		if (new_g > check->g) return AYSTAR_DONE;
		aystar->OpenListQueue.del(&aystar->OpenListQueue, 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];
		// Readd him in the OpenListQueue
		aystar->OpenListQueue.push(&aystar->OpenListQueue, check, new_f);
	} else {
		// A new node, add him to the OpenList
		AyStarMain_OpenList_Add(aystar, closedlist_parent, current, new_f, new_g);
	}

	return AYSTAR_DONE;
}

/*
 * 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 values:
 *	AYSTAR_EMPTY_OPENLIST : indicates all items are tested, and no path
 *	has been found.
 *	AYSTAR_LIMIT_REACHED : Indicates that the max_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 AyStarMain_Loop(AyStar *aystar) {
	int i, r;

	// Get the best node from OpenList
	OpenListNode *current = AyStarMain_OpenList_Pop(aystar);
	// If empty, drop an error
	if (current == NULL) return AYSTAR_EMPTY_OPENLIST;

	// Check for end node and if found, return that code
	if (aystar->EndNodeCheck(aystar, current) == AYSTAR_FOUND_END_NODE) {
		if (aystar->FoundEndNode != NULL)
			aystar->FoundEndNode(aystar, current);
		free(current);
		return AYSTAR_FOUND_END_NODE;
	}

	// Add the node to the ClosedList
	AyStarMain_ClosedList_Add(aystar, &current->path);

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

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

	// Free the node
	free(current);

	if (aystar->max_search_nodes != 0 && Hash_Size(&aystar->ClosedListHash) >= aystar->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 AyStarMain_Free(AyStar *aystar) {
	aystar->OpenListQueue.free(&aystar->OpenListQueue, false);
	/* 2nd argument above is false, below is true, to free the values only
	 * once */
	delete_Hash(&aystar->OpenListHash, true);
	delete_Hash(&aystar->ClosedListHash, 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 AyStarMain_Clear(AyStar *aystar) {
	// Clean the Queue, but not the elements within. That will be done by
	// the hash.
	aystar->OpenListQueue.clear(&aystar->OpenListQueue, false);
	// Clean the hashes
	clear_Hash(&aystar->OpenListHash, true);
	clear_Hash(&aystar->ClosedListHash, true);

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

/*
 * This is the function you call to run AyStar.
 *  return 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.
 * When the algorithm is done (when the return value is not AYSTAR_STILL_BUSY)
 * aystar->clear() is called. Note that when you stop the algorithm halfway,
 * you should still call clear() yourself!
 */
int AyStarMain_Main(AyStar *aystar) {
	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 = aystar->loop(aystar)) == AYSTAR_STILL_BUSY && (aystar->loops_per_tick == 0 || ++i < aystar->loops_per_tick)) { }
#ifdef AYSTAR_DEBUG
	if (r == AYSTAR_FOUND_END_NODE)
		printf("[AyStar] Found path!\n");
	else if (r == AYSTAR_EMPTY_OPENLIST)
		printf("[AyStar] OpenList run dry, no path found\n");
	else if (r == AYSTAR_LIMIT_REACHED)
		printf("[AyStar] Exceeded search_nodes, no path found\n");
#endif
	if (r != AYSTAR_STILL_BUSY)
		/* We're done, clean up */
		_aystar_stats_open_size = aystar->OpenListHash.size;
		_aystar_stats_closed_size = aystar->ClosedListHash.size;
		aystar->clear(aystar);

	// Check result-value
	if (r == AYSTAR_FOUND_END_NODE) return AYSTAR_FOUND_END_NODE;
	// Check if we have some left in the OpenList
	if (r == AYSTAR_EMPTY_OPENLIST || r == AYSTAR_LIMIT_REACHED) return AYSTAR_NO_PATH;

	// Return we are still busy
	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
 * g is the cost for starting with this node.
 */
void AyStarMain_AddStartNode(AyStar *aystar, 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
	AyStarMain_OpenList_Add(aystar, NULL, start_node, 0, g);
}

void init_AyStar(AyStar* aystar, Hash_HashProc hash, uint num_buckets) {
	// Allocated the Hash for the OpenList and ClosedList
	init_Hash(&aystar->OpenListHash, hash, num_buckets);
	init_Hash(&aystar->ClosedListHash, hash, num_buckets);

	// Set up our sorting queue
	//  BinaryHeap allocates a block of 1024 nodes
	//  When thatone gets full it reserves an otherone, till this number
	//  That is why it can stay this high
	init_BinaryHeap(&aystar->OpenListQueue, 102400);

	aystar->addstart	= AyStarMain_AddStartNode;
	aystar->main		= AyStarMain_Main;
	aystar->loop		= AyStarMain_Loop;
	aystar->free		= AyStarMain_Free;
	aystar->clear		= AyStarMain_Clear;
	aystar->checktile	= AyStarMain_CheckTile;
}