# aystar.cpp

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    00001 /* $Id: aystar.cpp 11691 2007-12-25 09:48:53Z rubidium $ */
    00002
    00005 /*
    00006  * This file has the core function for AyStar
    00007  *  AyStar is a fast pathfinding routine and is used for things like
    00008  *  AI_pathfinding and Train_pathfinding.
    00009  *  For more information about AyStar (A* Algorithm), you can look at
    00010  *    http://en.wikipedia.org/wiki/A-star_search_algorithm
    00011  */
    00012
    00013 /*
    00014  * Friendly reminder:
    00015  *  Call (AyStar).free() when you are done with Aystar. It reserves a lot of memory
    00016  *  And when not free'd, it can cause system-crashes.
    00017  * Also remember that when you stop an algorithm before it is finished, your
    00018  * should call clear() yourself!
    00019  */
    00020
    00021 #include "stdafx.h"
    00022 #include "openttd.h"
    00023 #include "aystar.h"
    00024 #include "core/alloc_func.hpp"
    00025
    00026 int _aystar_stats_open_size;
    00027 int _aystar_stats_closed_size;
    00028
    00029 // This looks in the Hash if a node exists in ClosedList
    00030 //  If so, it returns the PathNode, else NULL
    00031 static PathNode* AyStarMain_ClosedList_IsInList(AyStar *aystar, const AyStarNode *node)
    00032 {
    00033   return (PathNode*)Hash_Get(&aystar->ClosedListHash, node->tile, node->direction);
    00034 }
    00035
    00036 // This adds a node to the ClosedList
    00037 //  It makes a copy of the data
    00038 static void AyStarMain_ClosedList_Add(AyStar *aystar, const PathNode *node)
    00039 {
    00040   // Add a node to the ClosedList
    00041   PathNode *new_node = MallocT<PathNode>(1);
    00042   *new_node = *node;
    00043   Hash_Set(&aystar->ClosedListHash, node->node.tile, node->node.direction, new_node);
    00044 }
    00045
    00046 // Checks if a node is in the OpenList
    00047 //   If so, it returns the OpenListNode, else NULL
    00048 static OpenListNode *AyStarMain_OpenList_IsInList(AyStar *aystar, const AyStarNode *node)
    00049 {
    00050   return (OpenListNode*)Hash_Get(&aystar->OpenListHash, node->tile, node->direction);
    00051 }
    00052
    00053 // Gets the best node from OpenList
    00054 //  returns the best node, or NULL of none is found
    00055 // Also it deletes the node from the OpenList
    00056 static OpenListNode *AyStarMain_OpenList_Pop(AyStar *aystar)
    00057 {
    00058   // Return the item the Queue returns.. the best next OpenList item.
    00059   OpenListNode *res = (OpenListNode*)aystar->OpenListQueue.pop(&aystar->OpenListQueue);
    00060   if (res != NULL) {
    00061     Hash_Delete(&aystar->OpenListHash, res->path.node.tile, res->path.node.direction);
    00062   }
    00063
    00064   return res;
    00065 }
    00066
    00067 // Adds a node to the OpenList
    00068 //  It makes a copy of node, and puts the pointer of parent in the struct
    00069 static void AyStarMain_OpenList_Add(AyStar *aystar, PathNode *parent, const AyStarNode *node, int f, int g)
    00070 {
    00071   // Add a new Node to the OpenList
    00072   OpenListNode *new_node = MallocT<OpenListNode>(1);
    00073   new_node->g = g;
    00074   new_node->path.parent = parent;
    00075   new_node->path.node = *node;
    00076   Hash_Set(&aystar->OpenListHash, node->tile, node->direction, new_node);
    00077
    00078   // Add it to the queue
    00079   aystar->OpenListQueue.push(&aystar->OpenListQueue, new_node, f);
    00080 }
    00081
    00082 /*
    00083  * Checks one tile and calculate his f-value
    00084  *  return values:
    00085  * AYSTAR_DONE : indicates we are done
    00086  */
    00087 int AyStarMain_CheckTile(AyStar *aystar, AyStarNode *current, OpenListNode *parent)
    00088 {
    00089   int new_f, new_g, new_h;
    00090   PathNode *closedlist_parent;
    00091   OpenListNode *check;
    00092
    00093   // Check the new node against the ClosedList
    00094   if (AyStarMain_ClosedList_IsInList(aystar, current) != NULL) return AYSTAR_DONE;
    00095
    00096   // Calculate the G-value for this node
    00097   new_g = aystar->CalculateG(aystar, current, parent);
    00098   // If the value was INVALID_NODE, we don't do anything with this node
    00099   if (new_g == AYSTAR_INVALID_NODE) return AYSTAR_DONE;
    00100
    00101   // There should not be given any other error-code..
    00102   assert(new_g >= 0);
    00103   // Add the parent g-value to the new g-value
    00104   new_g += parent->g;
    00105   if (aystar->max_path_cost != 0 && (uint)new_g > aystar->max_path_cost) return AYSTAR_DONE;
    00106
    00107   // Calculate the h-value
    00108   new_h = aystar->CalculateH(aystar, current, parent);
    00109   // There should not be given any error-code..
    00110   assert(new_h >= 0);
    00111
    00112   // The f-value if g + h
    00113   new_f = new_g + new_h;
    00114
    00115   // Get the pointer to the parent in the ClosedList (the currentone is to a copy of the one in the OpenList)
    00116   closedlist_parent = AyStarMain_ClosedList_IsInList(aystar, &parent->path.node);
    00117
    00118   // Check if this item is already in the OpenList
    00119   check = AyStarMain_OpenList_IsInList(aystar, current);
    00120   if (check != NULL) {
    00121     uint i;
    00122     // Yes, check if this g value is lower..
    00123     if (new_g > check->g) return AYSTAR_DONE;
    00124     aystar->OpenListQueue.del(&aystar->OpenListQueue, check, 0);
    00125     // It is lower, so change it to this item
    00126     check->g = new_g;
    00127     check->path.parent = closedlist_parent;
    00128     /* Copy user data, will probably have changed */
    00129     for (i = 0; i < lengthof(current->user_data); i++) {
    00130       check->path.node.user_data[i] = current->user_data[i];
    00131     }
    00132     // Readd him in the OpenListQueue
    00133     aystar->OpenListQueue.push(&aystar->OpenListQueue, check, new_f);
    00134   } else {
    00135     // A new node, add him to the OpenList
    00136     AyStarMain_OpenList_Add(aystar, closedlist_parent, current, new_f, new_g);
    00137   }
    00138
    00139   return AYSTAR_DONE;
    00140 }
    00141
    00142 /*
    00143  * This function is the core of AyStar. It handles one item and checks
    00144  *  his neighbour items. If they are valid, they are added to be checked too.
    00145  *  return values:
    00146  *   AYSTAR_EMPTY_OPENLIST : indicates all items are tested, and no path
    00147  *    has been found.
    00148  *   AYSTAR_LIMIT_REACHED : Indicates that the max_nodes limit has been
    00149  *    reached.
    00150  *   AYSTAR_FOUND_END_NODE : indicates we found the end. Path_found now is true, and in path is the path found.
    00151  *   AYSTAR_STILL_BUSY : indicates we have done this tile, did not found the path yet, and have items left to try.
    00152  */
    00153 int AyStarMain_Loop(AyStar *aystar)
    00154 {
    00155   int i, r;
    00156
    00157   // Get the best node from OpenList
    00158   OpenListNode *current = AyStarMain_OpenList_Pop(aystar);
    00159   // If empty, drop an error
    00160   if (current == NULL) return AYSTAR_EMPTY_OPENLIST;
    00161
    00162   // Check for end node and if found, return that code
    00163   if (aystar->EndNodeCheck(aystar, current) == AYSTAR_FOUND_END_NODE) {
    00164     if (aystar->FoundEndNode != NULL)
    00165       aystar->FoundEndNode(aystar, current);
    00166     free(current);
    00167     return AYSTAR_FOUND_END_NODE;
    00168   }
    00169
    00170   // Add the node to the ClosedList
    00171   AyStarMain_ClosedList_Add(aystar, &current->path);
    00172
    00173   // Load the neighbours
    00174   aystar->GetNeighbours(aystar, current);
    00175
    00176   // Go through all neighbours
    00177   for (i = 0; i < aystar->num_neighbours; i++) {
    00178     // Check and add them to the OpenList if needed
    00179     r = aystar->checktile(aystar, &aystar->neighbours[i], current);
    00180   }
    00181
    00182   // Free the node
    00183   free(current);
    00184
    00185   if (aystar->max_search_nodes != 0 && Hash_Size(&aystar->ClosedListHash) >= aystar->max_search_nodes) {
    00186     /* We've expanded enough nodes */
    00187     return AYSTAR_LIMIT_REACHED;
    00188   } else {
    00189     // Return that we are still busy
    00190     return AYSTAR_STILL_BUSY;
    00191   }
    00192 }
    00193
    00194 /*
    00195  * This function frees the memory it allocated
    00196  */
    00197 void AyStarMain_Free(AyStar *aystar)
    00198 {
    00199   aystar->OpenListQueue.free(&aystar->OpenListQueue, false);
    00200   /* 2nd argument above is false, below is true, to free the values only
    00201    * once */
    00202   delete_Hash(&aystar->OpenListHash, true);
    00203   delete_Hash(&aystar->ClosedListHash, true);
    00204 #ifdef AYSTAR_DEBUG
    00205   printf("[AyStar] Memory free'd\n");
    00206 #endif
    00207 }
    00208
    00209 /*
    00210  * This function make the memory go back to zero
    00211  *  This function should be called when you are using the same instance again.
    00212  */
    00213 void AyStarMain_Clear(AyStar *aystar)
    00214 {
    00215   // Clean the Queue, but not the elements within. That will be done by
    00216   // the hash.
    00217   aystar->OpenListQueue.clear(&aystar->OpenListQueue, false);
    00218   // Clean the hashes
    00219   clear_Hash(&aystar->OpenListHash, true);
    00220   clear_Hash(&aystar->ClosedListHash, true);
    00221
    00222 #ifdef AYSTAR_DEBUG
    00223   printf("[AyStar] Cleared AyStar\n");
    00224 #endif
    00225 }
    00226
    00227 /*
    00228  * This is the function you call to run AyStar.
    00229  *  return values:
    00230  *   AYSTAR_FOUND_END_NODE : indicates we found an end node.
    00231  *   AYSTAR_NO_PATH : indicates that there was no path found.
    00232  *   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.
    00233  * When the algorithm is done (when the return value is not AYSTAR_STILL_BUSY)
    00234  * aystar->clear() is called. Note that when you stop the algorithm halfway,
    00235  * you should still call clear() yourself!
    00236  */
    00237 int AyStarMain_Main(AyStar *aystar) {
    00238   int r, i = 0;
    00239   // Loop through the OpenList
    00240   //  Quit if result is no AYSTAR_STILL_BUSY or is more than loops_per_tick
    00241   while ((r = aystar->loop(aystar)) == AYSTAR_STILL_BUSY && (aystar->loops_per_tick == 0 || ++i < aystar->loops_per_tick)) { }
    00242 #ifdef AYSTAR_DEBUG
    00243   switch (r) {
    00244     case AYSTAR_FOUND_END_NODE: printf("[AyStar] Found path!\n"); break;
    00245     case AYSTAR_EMPTY_OPENLIST: printf("[AyStar] OpenList run dry, no path found\n"); break;
    00246     case AYSTAR_LIMIT_REACHED:  printf("[AyStar] Exceeded search_nodes, no path found\n"); break;
    00247     default: break;
    00248   }
    00249 #endif
    00250   if (r != AYSTAR_STILL_BUSY) {
    00251     /* We're done, clean up */
    00252     _aystar_stats_open_size = aystar->OpenListHash.size;
    00253     _aystar_stats_closed_size = aystar->ClosedListHash.size;
    00254     aystar->clear(aystar);
    00255   }
    00256
    00257   switch (r) {
    00258     case AYSTAR_FOUND_END_NODE: return AYSTAR_FOUND_END_NODE;
    00259     case AYSTAR_EMPTY_OPENLIST:
    00260     case AYSTAR_LIMIT_REACHED:  return AYSTAR_NO_PATH;
    00261     default:                    return AYSTAR_STILL_BUSY;
    00262   }
    00263 }
    00264
    00265 /*
    00266  * Adds a node from where to start an algorithm. Multiple nodes can be added
    00267  * if wanted. You should make sure that clear() is called before adding nodes
    00268  * if the AyStar has been used before (though the normal main loop calls
    00269  * clear() automatically when the algorithm finishes
    00270  * g is the cost for starting with this node.
    00271  */
    00272 void AyStarMain_AddStartNode(AyStar *aystar, AyStarNode *start_node, uint g)
    00273 {
    00274 #ifdef AYSTAR_DEBUG
    00275   printf("[AyStar] Starting A* Algorithm from node (%d, %d, %d)\n",
    00276     TileX(start_node->tile), TileY(start_node->tile), start_node->direction);
    00277 #endif
    00278   AyStarMain_OpenList_Add(aystar, NULL, start_node, 0, g);
    00279 }
    00280
    00281 void init_AyStar(AyStar *aystar, Hash_HashProc hash, uint num_buckets)
    00282 {
    00283   // Allocated the Hash for the OpenList and ClosedList
    00284   init_Hash(&aystar->OpenListHash, hash, num_buckets);
    00285   init_Hash(&aystar->ClosedListHash, hash, num_buckets);
    00286
    00287   // Set up our sorting queue
    00288   //  BinaryHeap allocates a block of 1024 nodes
    00289   //  When thatone gets full it reserves an otherone, till this number
    00290   //  That is why it can stay this high
    00291   init_BinaryHeap(&aystar->OpenListQueue, 102400);
    00292
    00293   aystar->addstart  = AyStarMain_AddStartNode;
    00294   aystar->main      = AyStarMain_Main;
    00295   aystar->loop      = AyStarMain_Loop;
    00296   aystar->free      = AyStarMain_Free;
    00297   aystar->clear     = AyStarMain_Clear;
    00298   aystar->checktile = AyStarMain_CheckTile;
    00299 }