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/* $Id$ */
/*
* 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 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 "../../core/alloc_func.hpp"
#include "aystar.h"
/* 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, const 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, const PathNode *node)
{
/* Add a node to the ClosedList */
PathNode *new_node = MallocT<PathNode>(1);
*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, const 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 */
OpenListNode *AyStar::OpenListPop()
{
/* Return the item the Queue returns.. the best next OpenList item. */
OpenListNode *res = (OpenListNode*)this->OpenListQueue.Pop();
if (res != NULL) {
Hash_Delete(&this->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 */
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;
Hash_Set(&this->OpenListHash, node->tile, node->direction, new_node);
/* Add it to the queue */
this->OpenListQueue.Push(new_node, f);
}
/*
* Checks one tile and calculate his 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 (AyStarMain_ClosedList_IsInList(this, current) != NULL) 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 currentone is to a copy of the one in the OpenList) */
closedlist_parent = AyStarMain_ClosedList_IsInList(this, &parent->path.node);
/* Check if this item is already in the OpenList */
check = AyStarMain_OpenList_IsInList(this, current);
if (check != NULL) {
uint i;
/* Yes, check if this g value is lower.. */
if (new_g > check->g) return;
this->OpenListQueue.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];
}
/* Readd him in the OpenListQueue */
this->OpenListQueue.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 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 AyStar::Loop()
{
int i;
/* Get the best node from OpenList */
OpenListNode *current = this->OpenListPop();
/* If empty, drop an error */
if (current == NULL) return AYSTAR_EMPTY_OPENLIST;
/* Check for end node and if found, return that code */
if (this->EndNodeCheck(this, current) == AYSTAR_FOUND_END_NODE) {
if (this->FoundEndNode != NULL) {
this->FoundEndNode(this, current);
}
free(current);
return AYSTAR_FOUND_END_NODE;
}
/* Add the node to the ClosedList */
AyStarMain_ClosedList_Add(this, ¤t->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 && Hash_Size(&this->ClosedListHash) >= 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->OpenListQueue.Free(false);
/* 2nd argument above is false, below is true, to free the values only
* once */
delete_Hash(&this->OpenListHash, true);
delete_Hash(&this->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 AyStar::Clear()
{
/* Clean the Queue, but not the elements within. That will be done by
* the hash. */
this->OpenListQueue.Clear(false);
/* Clean the hashes */
clear_Hash(&this->OpenListHash, true);
clear_Hash(&this->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)
* this->Clear() is called. Note that when you stop the algorithm halfway,
* you should still 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
* g is 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(NULL, 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 */
init_Hash(&this->OpenListHash, hash, num_buckets);
init_Hash(&this->ClosedListHash, 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->OpenListQueue.Init(102400);
}
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