server/include/micropather.h

/*
Copyright (c) 2000-2003 Lee Thomason (www.grinninglizard.com)
Grinning Lizard Utilities.

This software is provided 'as-is', without any express or implied 
warranty. In no event will the authors be held liable for any 
damages arising from the use of this software.

Permission is granted to anyone to use this software for any 
purpose, including commercial applications, and to alter it and 
redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must 
not claim that you wrote the original software. If you use this 
software in a product, an acknowledgment in the product documentation 
would be appreciated but is not required.

2. Altered source versions must be plainly marked as such, and 
must not be misrepresented as being the original software.

3. This notice may not be removed or altered from any source 
distribution.
*/


#ifndef GRINNINGLIZARD_MICROPATHER_INCLUDED
#define GRINNINGLIZARD_MICROPATHER_INCLUDED

/** @mainpage MicroPather
        
        MicroPather is a path finder and A* solver (astar or a-star) written in platform independent 
        C++ that can be easily integrated into existing code. MicroPather focuses on being a path 
        finding engine for video games but is a generic A* solver. MicroPather is open source, with 
        a license suitable for open source or commercial use.

        An overview of using MicroPather is in the <A HREF="../readme.htm">readme</A> or
        on the Grinning Lizard website: http://grinninglizard.com/micropather/
*/

#include <vector>
#include <list>
#include <assert.h>
#include <float.h>

#ifdef _DEBUG
        #ifndef DEBUG
                #define DEBUG
        #endif
#endif

#ifndef GRINLIZ_TYPES_INCLUDED
        #if defined(_MSC_VER) && (_MSC_VER >= 1400 )
                #include <stdlib.h>
                typedef uintptr_t               UPTR;
        #else
                #include <stdint.h>
                typedef uintptr_t               UPTR;
        #endif
#endif

/*  USE_LIST and USE_BINARY_HASH change the some of details the pather algorithms. They
        are set optimally in my experiments, but different applications may benefit
        from a different combination of these #defines.
*/
#define USE_LIST
//#define USE_BINARY_HASH

namespace micropather
{
        const float FLT_BIG = FLT_MAX / 2.0f;   

        /**
                Used to pass the cost of states from the cliet application to MicroPather. This
                structure is copied in a vector.

                @sa AdjacentCost
        */
        struct StateCost
        {
                void* state;                    ///< The state as a void*
                float cost;                             ///< The cost to the state. Use FLT_MAX for infinite cost.
        };


        /**
                A pure abstract class used to define a set of callbacks. 
                The client application inherits from 
                this class, and the methods will be called when MicroPather::Solve() is invoked.

                The notion of a "state" is very important. It must have the following properties:
                - Unique
                - Unchanging (unless MicroPather::Reset() is called)

                If the client application represents states as objects, then the state is usually
                just the object cast to a void*. If the client application sees states as numerical
                values, (x,y) for example, then state is an encoding of these values. MicroPather
                never interprets or modifies the value of state.
        */
        class Graph
        {
          public:
                virtual ~Graph() {}
          
                /**
                        Return the least possible cost between 2 states. For example, if your pathfinding 
                        is based on distance, this is simply the straight distance between 2 points on the 
                        map. If you pathfinding is based on minimum time, it is the minimal travel time 
                        between 2 points given the best possible terrain.
                */
                virtual float LeastCostEstimate( void* stateStart, void* stateEnd ) = 0;

                /** 
                        Return the exact cost from the given state to all its neighboring states. This
                        may be called multiple times, or cached by the solver. It *must* return the same
                        exact values for every call to MicroPather::Solve(). It should generally be a simple,
                        fast function with no callbacks into the pather.
                */
                virtual void AdjacentCost( void* state, std::vector< micropather::StateCost > *adjacent ) = 0;

                /**
                        This function is only used in DEBUG mode - it dumps output to stdout. Since void* 
                        aren't really human readable, normally you print out some concise info (like "(1,2)") 
                        without an ending newline.

                        @note If you are using other grinning lizard utilities, you should use GLOUTPUT for output.
                */
                virtual void  PrintStateInfo( void* state ) = 0;
        };


        class PathNode;

        struct NodeCost
        {
                PathNode* node;
                float cost;
        };


        class PathNode
        {
                friend class none;      // Trashy trick to get rid of compiler warning, because
                                                // this class has a private constructor and destructor -
                                                // it can never be "new" or created on the stack, only
                                                // by special allocators.
          public:
                void Init(      unsigned _frame,
                                        void* _state,
                                        float _costFromStart, 
                                        float _estToGoal, 
                                        PathNode* _parent )
                {
                        state = _state;
                        costFromStart = _costFromStart;
                        estToGoal = _estToGoal;
                        totalCost = _costFromStart + _estToGoal;
                        parent = _parent;
                        frame = _frame;
                        numAdjacent = -1;
                        left = 0;
                        #ifdef USE_BINARY_HASH
                        right = 0;
                        #endif
                        #ifdef USE_LIST
                        next = 0;
                        prev = 0;
                        #endif
                        inOpen = 0;
                        inClosed = 0;
                }

                void Reuse( unsigned _frame, float _costFromStart, float _estToGoal, PathNode* _parent ) 
                {
                        costFromStart = _costFromStart;
                        estToGoal = _estToGoal;
                        parent = _parent;
                        frame = _frame;

                        inOpen = 0;
                        inClosed = 0;
                }

                void *state;                    // the client state
                float costFromStart;    // exact
                float estToGoal;                // estimated
                float totalCost;                // could be a function, but save some math.
                PathNode* parent;               // the parent is used to reconstruct the path
                unsigned frame;                 // unique id for this path, so the solver can distinguish
                                                                // correct from stale values

                enum {
                        /*
                                @enum MAX_CACHE. If you want to optimize "down deep" this is the way
                                to go. MAX_CACHE determines the number of adjacent nodes cached by 
                                MicroPather. If your nodes generally have 8 or 3 neighbors (common cases)
                                changing this may increase performance, sometimes dramatically.
                        */
                        MAX_CACHE = 8
                };
                // If there are 4 or less adjacent states, they will be cached as *nodes*.
                NodeCost adjacent[ MAX_CACHE ];
                int numAdjacent;                                        // -1  is unknown & needs to be queried
                                                                                        // 0-4 adjacent is known & in 'adjacent'
                                                                                        // 5+  known, but has to be queried from Graph

                PathNode* left;                 // Binary tree, where the 'state' is what is being compared.
                                                                // Also used as a "next" pointer for memory layout.
                #ifdef USE_BINARY_HASH
                PathNode* right;
                #endif
                #ifdef USE_LIST
                PathNode *next, *prev;
                #endif

                unsigned inOpen:1;
                unsigned inClosed:1;

                #ifdef USE_LIST
                void Unlink() {
                        next->prev = prev;
                        prev->next = next;
                        next = prev = 0;
                }
                void AddBefore( PathNode* addThis ) {
                        addThis->next = this;
                        addThis->prev = prev;
                        prev->next = addThis;
                        prev = addThis;
                }
                #ifdef DEBUG
                void CheckList()
                {
                        assert( totalCost == FLT_MAX );
                        for( PathNode* it = next; it != this; it=it->next ) {
                                assert( it->prev == this || it->totalCost >= it->prev->totalCost );
                                assert( it->totalCost <= it->next->totalCost );
                        }
                }
                #endif
                #endif

          private:
                PathNode();
                ~PathNode();
                PathNode( const PathNode& );
                void operator=( const PathNode& );
        };


        /**
                Create a MicroPather object to solve for a best path. Detailed usage notes are
                on the main page.
        */
        class MicroPather
        {
                friend class micropather::PathNode;

          public:
                enum
                {
                        SOLVED,
                        NO_SOLUTION,
                        START_END_SAME,
                };

                /**
                        Construct the pather, passing a pointer to the object that implements
                        the Graph callbacks.

                        @param graph            The "map" that implements the Graph callbacks.
                        @param allocate         The block size that the node cache is allocated from. In some
                                                                cases setting this parameter will improve the perfomance of
                                                                the pather.
                                                                - If you have a small map, for example the size of a chessboard, set allocate
                                                                  to be the number of states+1. 65 for a chessboard. This will allow
                                                                  MicroPather to used a fixed amount of memory.
                                                                - If your map is large, something like 1/4 the number of possible
                                                                  states is good. For example, Lilith3D normally has about 16,000 
                                                                  states, so 'allocate' should be about 4000.
                */
                MicroPather( Graph* graph, unsigned allocate = 250 );
                ~MicroPather();

                /**
                        Solve for the path from start to end.

                        @param startState       Input, the starting state for the path.
                        @param endState         Input, the ending state for the path.
                        @param path                     Output, a vector of states that define the path. Empty if not found.
                        @param totalCost        Output, the cost of the path, if found.
                        @return                         Success or failure, expressed as SOLVED, NO_SOLUTION, or START_END_SAME.
                */
                int Solve( void* startState, void* endState, std::vector< void* >* path, float* totalCost );

                /// Should be called whenever the cost between states or the connection between states changes.
                void Reset();

                /*  Deprecated. Too complex for the practical value.
                        @warning It is very easy to "miss" a state that needs to be changed and break the pather.

                        As described on the main page, it is possible to change the costs (but not the connections)
                        of states without calling Reset(). Be sure that all effected states are passed to
                        StateCostChange.
                */
                //void StateCostChange( void* state );

                /**
                        Return the "checksum" of the last path returned by Solve(). Useful for debugging,
                        and a quick way to see if 2 paths are the same.
                */
                UPTR Checksum() { return checksum; }
                
                void DumpHashTable();
                
                // Debugging function to return all states that were used
                // by the last "solve" 
                void StatesInPool( std::vector< void* >* stateVec );

          private:
                MicroPather( const MicroPather& );      // undefined and unsupported
                void operator=( const MicroPather ); // undefined and unsupported
                
                void GoalReached( PathNode* node, void* start, void* end, std::vector< void* > *path );
                void RecPathNodeWalk( PathNode* node, int* count );
                
                // Allocates and returns memory for a new, unititialized node.
                PathNode* AllocatePathNode();

                // Returns a path node that is ready to go. 
                // Strictly speaking, the name is somewhat misleading, as it
                // may be reused from the cache, but it will be ready for use regardless.
                PathNode* NewPathNode( void* state, float costFromStart, float estToEnd, PathNode* parent );

                // Finds the node for state, or returns null. 
                // A node that doesn't have a correct "frame" will never be found.
                PathNode* FindPathNode( void* state, bool findStale = false ); 

                NodeCost* GetNodeNeighbors( PathNode* node, std::vector< StateCost >* neighbor, std::vector< NodeCost >* neighborNode );

                #ifdef DEBUG
                void DumpStats();
                #endif

                enum {
                        #ifdef DEBUG_PATH
                        HASH_SIZE = 16,         // In debug mode, stress the allocators more than in release.
                                                                        // The HASH_SIZE must be a power of 2.
                        #else
                        HASH_SIZE = 256,
                        #endif
                };

        unsigned Hash( void* voidval ) {
                        UPTR val = (UPTR)voidval;
            return (unsigned)((HASH_SIZE-1) & ( val + (val>>8) + (val>>16) + (val>>24) ));
        }    
    
                const unsigned ALLOCATE;                        // how big a block of pathnodes to allocate at once
                const unsigned BLOCKSIZE;                       // how many useable pathnodes are in a block

                Graph* graph;
                PathNode* hashTable[HASH_SIZE];         // a fixed hashtable used to "jumpstart" a binary search
                PathNode* pathNodeMem;                          // pointer to root of PathNode blocks
                unsigned availMem;                                      // # PathNodes available in the current block
                unsigned pathNodeCount;                         // the # of PathNodes in use
                unsigned frame;                                         // incremented with every solve, used to determine
                                                                                        // if cached data needs to be refreshed
                UPTR checksum;                                  // the checksum of the last successful "Solve".

                std::vector< StateCost > neighborVec;   // really local vars to Solve, but put here to reduce memory allocation
                std::vector< NodeCost > neighborNodeVec; // really local vars to Solve, but put here to reduce memory allocation
        };

        inline PathNode* MicroPather::FindPathNode( void* state, bool findStale )
        {
                unsigned key = Hash( state );

                PathNode* root = hashTable[key];
                #ifdef USE_BINARY_HASH
                while ( root ) {
                        if ( root->state == state ) {
                                if ( findStale || root->frame == frame )
                                        return root;
                                else
                                        return 0;
                        }
                        else if ( state > root->state ) {
                                root = root->right;
                        }
                        else {
                                assert( state < root->state );
                                root = root->left;
                        }
                }
                #else
                while( root ) {
                        if ( root->state == state ) {
                                if ( findStale || root->frame == frame )
                                        return root;
                                else
                                        return 0;
                        }
                        else {
                                root = root->left;
                        }
                }
                #endif
                return 0;
        }               
};      // namespace grinliz

#endif

Revision:	1.4
Committed:	Sat Apr 23 04:50:24 2011 UTC (13 years, 1 month ago) by root
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.3:	+0 -0 lines
State:	*FILE REMOVED*
Log Message:	removed micropather
#	User	Rev	Content
1	root	1.1	/*
2			Copyright (c) 2000-2003 Lee Thomason (www.grinninglizard.com)
3			Grinning Lizard Utilities.
4
5			This software is provided 'as-is', without any express or implied
6			warranty. In no event will the authors be held liable for any
7			damages arising from the use of this software.
8
9			Permission is granted to anyone to use this software for any
10			purpose, including commercial applications, and to alter it and
11			redistribute it freely, subject to the following restrictions:
12
13			1. The origin of this software must not be misrepresented; you must
14			not claim that you wrote the original software. If you use this
15			software in a product, an acknowledgment in the product documentation
16			would be appreciated but is not required.
17
18			2. Altered source versions must be plainly marked as such, and
19			must not be misrepresented as being the original software.
20
21			3. This notice may not be removed or altered from any source
22			distribution.
23			*/
24
25
26			#ifndef GRINNINGLIZARD_MICROPATHER_INCLUDED
27			#define GRINNINGLIZARD_MICROPATHER_INCLUDED
28
29			/** @mainpage MicroPather
30
31			MicroPather is a path finder and A* solver (astar or a-star) written in platform independent
32			C++ that can be easily integrated into existing code. MicroPather focuses on being a path
33			finding engine for video games but is a generic A* solver. MicroPather is open source, with
34			a license suitable for open source or commercial use.
35
36			An overview of using MicroPather is in the <A HREF="../readme.htm">readme</A> or
37			on the Grinning Lizard website: http://grinninglizard.com/micropather/
38			*/
39
40			#include <vector>
41			#include <list>
42			#include <assert.h>
43			#include <float.h>
44
45			#ifdef _DEBUG
46			#ifndef DEBUG
47			#define DEBUG
48			#endif
49			#endif
50
51			#ifndef GRINLIZ_TYPES_INCLUDED
52			#if defined(_MSC_VER) && (_MSC_VER >= 1400 )
53			#include <stdlib.h>
54			typedef uintptr_t UPTR;
55	root	1.2	#else
56			#include <stdint.h>
57	root	1.1	typedef uintptr_t UPTR;
58			#endif
59			#endif
60
61			/* USE_LIST and USE_BINARY_HASH change the some of details the pather algorithms. They
62			are set optimally in my experiments, but different applications may benefit
63			from a different combination of these #defines.
64			*/
65			#define USE_LIST
66			//#define USE_BINARY_HASH
67
68			namespace micropather
69			{
70			const float FLT_BIG = FLT_MAX / 2.0f;
71
72			/**
73			Used to pass the cost of states from the cliet application to MicroPather. This
74			structure is copied in a vector.
75
76			@sa AdjacentCost
77			*/
78			struct StateCost
79			{
80			void* state; ///< The state as a void*
81			float cost; ///< The cost to the state. Use FLT_MAX for infinite cost.
82			};
83
84
85			/**
86			A pure abstract class used to define a set of callbacks.
87			The client application inherits from
88			this class, and the methods will be called when MicroPather::Solve() is invoked.
89
90			The notion of a "state" is very important. It must have the following properties:
91			- Unique
92			- Unchanging (unless MicroPather::Reset() is called)
93
94			If the client application represents states as objects, then the state is usually
95			just the object cast to a void*. If the client application sees states as numerical
96			values, (x,y) for example, then state is an encoding of these values. MicroPather
97			never interprets or modifies the value of state.
98			*/
99			class Graph
100			{
101			public:
102			virtual ~Graph() {}
103
104			/**
105			Return the least possible cost between 2 states. For example, if your pathfinding
106			is based on distance, this is simply the straight distance between 2 points on the
107			map. If you pathfinding is based on minimum time, it is the minimal travel time
108			between 2 points given the best possible terrain.
109			*/
110			virtual float LeastCostEstimate( void* stateStart, void* stateEnd ) = 0;
111
112			/**
113			Return the exact cost from the given state to all its neighboring states. This
114			may be called multiple times, or cached by the solver. It must return the same
115			exact values for every call to MicroPather::Solve(). It should generally be a simple,
116			fast function with no callbacks into the pather.
117			*/
118			virtual void AdjacentCost( void* state, std::vector< micropather::StateCost > *adjacent ) = 0;
119
120			/**
121			This function is only used in DEBUG mode - it dumps output to stdout. Since void*
122			aren't really human readable, normally you print out some concise info (like "(1,2)")
123			without an ending newline.
124
125			@note If you are using other grinning lizard utilities, you should use GLOUTPUT for output.
126			*/
127			virtual void PrintStateInfo( void* state ) = 0;
128			};
129
130
131			class PathNode;
132
133			struct NodeCost
134			{
135			PathNode* node;
136			float cost;
137			};
138
139
140			class PathNode
141			{
142			friend class none; // Trashy trick to get rid of compiler warning, because
143			// this class has a private constructor and destructor -
144			// it can never be "new" or created on the stack, only
145			// by special allocators.
146			public:
147			void Init( unsigned _frame,
148			void* _state,
149			float _costFromStart,
150			float _estToGoal,
151			PathNode* _parent )
152			{
153			state = _state;
154			costFromStart = _costFromStart;
155			estToGoal = _estToGoal;
156			totalCost = _costFromStart + _estToGoal;
157			parent = _parent;
158			frame = _frame;
159			numAdjacent = -1;
160			left = 0;
161			#ifdef USE_BINARY_HASH
162			right = 0;
163			#endif
164			#ifdef USE_LIST
165			next = 0;
166			prev = 0;
167			#endif
168			inOpen = 0;
169			inClosed = 0;
170			}
171
172			void Reuse( unsigned _frame, float _costFromStart, float _estToGoal, PathNode* _parent )
173			{
174			costFromStart = _costFromStart;
175			estToGoal = _estToGoal;
176			parent = _parent;
177			frame = _frame;
178
179			inOpen = 0;
180			inClosed = 0;
181			}
182
183			void *state; // the client state
184			float costFromStart; // exact
185			float estToGoal; // estimated
186			float totalCost; // could be a function, but save some math.
187			PathNode* parent; // the parent is used to reconstruct the path
188			unsigned frame; // unique id for this path, so the solver can distinguish
189			// correct from stale values
190
191			enum {
192			/*
193			@enum MAX_CACHE. If you want to optimize "down deep" this is the way
194			to go. MAX_CACHE determines the number of adjacent nodes cached by
195			MicroPather. If your nodes generally have 8 or 3 neighbors (common cases)
196			changing this may increase performance, sometimes dramatically.
197			*/
198	root	1.3	MAX_CACHE = 8
199	root	1.1	};
200			// If there are 4 or less adjacent states, they will be cached as nodes.
201			NodeCost adjacent[ MAX_CACHE ];
202			int numAdjacent; // -1 is unknown & needs to be queried
203			// 0-4 adjacent is known & in 'adjacent'
204			// 5+ known, but has to be queried from Graph
205
206			PathNode* left; // Binary tree, where the 'state' is what is being compared.
207			// Also used as a "next" pointer for memory layout.
208			#ifdef USE_BINARY_HASH
209			PathNode* right;
210			#endif
211			#ifdef USE_LIST
212			PathNode next, prev;
213			#endif
214
215			unsigned inOpen:1;
216			unsigned inClosed:1;
217
218			#ifdef USE_LIST
219			void Unlink() {
220			next->prev = prev;
221			prev->next = next;
222			next = prev = 0;
223			}
224			void AddBefore( PathNode* addThis ) {
225			addThis->next = this;
226			addThis->prev = prev;
227			prev->next = addThis;
228			prev = addThis;
229			}
230			#ifdef DEBUG
231			void CheckList()
232			{
233			assert( totalCost == FLT_MAX );
234			for( PathNode* it = next; it != this; it=it->next ) {
235			assert( it->prev == this \|\| it->totalCost >= it->prev->totalCost );
236			assert( it->totalCost <= it->next->totalCost );
237			}
238			}
239			#endif
240			#endif
241
242			private:
243			PathNode();
244			~PathNode();
245			PathNode( const PathNode& );
246			void operator=( const PathNode& );
247			};
248
249
250			/**
251			Create a MicroPather object to solve for a best path. Detailed usage notes are
252			on the main page.
253			*/
254			class MicroPather
255			{
256			friend class micropather::PathNode;
257
258			public:
259			enum
260			{
261			SOLVED,
262			NO_SOLUTION,
263			START_END_SAME,
264			};
265
266			/**
267			Construct the pather, passing a pointer to the object that implements
268			the Graph callbacks.
269
270			@param graph The "map" that implements the Graph callbacks.
271			@param allocate The block size that the node cache is allocated from. In some
272			cases setting this parameter will improve the perfomance of
273			the pather.
274			- If you have a small map, for example the size of a chessboard, set allocate
275			to be the number of states+1. 65 for a chessboard. This will allow
276			MicroPather to used a fixed amount of memory.
277			- If your map is large, something like 1/4 the number of possible
278			states is good. For example, Lilith3D normally has about 16,000
279			states, so 'allocate' should be about 4000.
280			*/
281			MicroPather( Graph* graph, unsigned allocate = 250 );
282			~MicroPather();
283
284			/**
285			Solve for the path from start to end.
286
287			@param startState Input, the starting state for the path.
288			@param endState Input, the ending state for the path.
289			@param path Output, a vector of states that define the path. Empty if not found.
290			@param totalCost Output, the cost of the path, if found.
291			@return Success or failure, expressed as SOLVED, NO_SOLUTION, or START_END_SAME.
292			*/
293			int Solve( void* startState, void* endState, std::vector< void* >* path, float* totalCost );
294
295			/// Should be called whenever the cost between states or the connection between states changes.
296			void Reset();
297
298			/* Deprecated. Too complex for the practical value.
299			@warning It is very easy to "miss" a state that needs to be changed and break the pather.
300
301			As described on the main page, it is possible to change the costs (but not the connections)
302			of states without calling Reset(). Be sure that all effected states are passed to
303			StateCostChange.
304			*/
305			//void StateCostChange( void* state );
306
307			/**
308			Return the "checksum" of the last path returned by Solve(). Useful for debugging,
309			and a quick way to see if 2 paths are the same.
310			*/
311			UPTR Checksum() { return checksum; }
312
313			void DumpHashTable();
314
315			// Debugging function to return all states that were used
316			// by the last "solve"
317			void StatesInPool( std::vector< void* >* stateVec );
318
319			private:
320			MicroPather( const MicroPather& ); // undefined and unsupported
321			void operator=( const MicroPather ); // undefined and unsupported
322
323			void GoalReached( PathNode* node, void* start, void* end, std::vector< void* > *path );
324			void RecPathNodeWalk( PathNode* node, int* count );
325
326			// Allocates and returns memory for a new, unititialized node.
327			PathNode* AllocatePathNode();
328
329			// Returns a path node that is ready to go.
330			// Strictly speaking, the name is somewhat misleading, as it
331			// may be reused from the cache, but it will be ready for use regardless.
332			PathNode* NewPathNode( void* state, float costFromStart, float estToEnd, PathNode* parent );
333
334			// Finds the node for state, or returns null.
335			// A node that doesn't have a correct "frame" will never be found.
336			PathNode* FindPathNode( void* state, bool findStale = false );
337
338			NodeCost* GetNodeNeighbors( PathNode* node, std::vector< StateCost >* neighbor, std::vector< NodeCost >* neighborNode );
339
340			#ifdef DEBUG
341			void DumpStats();
342			#endif
343
344			enum {
345			#ifdef DEBUG_PATH
346			HASH_SIZE = 16, // In debug mode, stress the allocators more than in release.
347			// The HASH_SIZE must be a power of 2.
348			#else
349			HASH_SIZE = 256,
350			#endif
351			};
352
353			unsigned Hash( void* voidval ) {
354			UPTR val = (UPTR)voidval;
355			return (unsigned)((HASH_SIZE-1) & ( val + (val>>8) + (val>>16) + (val>>24) ));
356			}
357
358			const unsigned ALLOCATE; // how big a block of pathnodes to allocate at once
359			const unsigned BLOCKSIZE; // how many useable pathnodes are in a block
360
361			Graph* graph;
362			PathNode* hashTable[HASH_SIZE]; // a fixed hashtable used to "jumpstart" a binary search
363			PathNode* pathNodeMem; // pointer to root of PathNode blocks
364			unsigned availMem; // # PathNodes available in the current block
365			unsigned pathNodeCount; // the # of PathNodes in use
366			unsigned frame; // incremented with every solve, used to determine
367			// if cached data needs to be refreshed
368			UPTR checksum; // the checksum of the last successful "Solve".
369
370			std::vector< StateCost > neighborVec; // really local vars to Solve, but put here to reduce memory allocation
371			std::vector< NodeCost > neighborNodeVec; // really local vars to Solve, but put here to reduce memory allocation
372			};
373
374			inline PathNode* MicroPather::FindPathNode( void* state, bool findStale )
375			{
376			unsigned key = Hash( state );
377
378			PathNode* root = hashTable[key];
379			#ifdef USE_BINARY_HASH
380			while ( root ) {
381			if ( root->state == state ) {
382			if ( findStale \|\| root->frame == frame )
383			return root;
384			else
385			return 0;
386			}
387			else if ( state > root->state ) {
388			root = root->right;
389			}
390			else {
391			assert( state < root->state );
392			root = root->left;
393			}
394			}
395			#else
396			while( root ) {
397			if ( root->state == state ) {
398			if ( findStale \|\| root->frame == frame )
399			return root;
400			else
401			return 0;
402			}
403			else {
404			root = root->left;
405			}
406			}
407			#endif
408			return 0;
409			}
410			}; // namespace grinliz
411
412			#endif
413