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source: code/trunk/src/external/bullet/BulletCollision/CollisionDispatch/btUnionFind.h @ 10552

Last change on this file since 10552 was 8393, checked in by rgrieder, 14 years ago

Updated Bullet from v2.77 to v2.78.
(I'm not going to make a branch for that since the update from 2.74 to 2.77 hasn't been tested that much either).

You will HAVE to do a complete RECOMPILE! I tested with MSVC and MinGW and they both threw linker errors at me.

  • Property svn:eol-style set to native
File size: 3.4 KB
Line 
1/*
2Bullet Continuous Collision Detection and Physics Library
3Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/
4
5This software is provided 'as-is', without any express or implied warranty.
6In no event will the authors be held liable for any damages arising from the use of this software.
7Permission is granted to anyone to use this software for any purpose,
8including commercial applications, and to alter it and redistribute it freely,
9subject to the following restrictions:
10
111. 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.
122. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
133. This notice may not be removed or altered from any source distribution.
14*/
15
16#ifndef BT_UNION_FIND_H
17#define BT_UNION_FIND_H
18
19#include "LinearMath/btAlignedObjectArray.h"
20
21#define USE_PATH_COMPRESSION 1
22
23///see for discussion of static island optimizations by Vroonsh here: http://code.google.com/p/bullet/issues/detail?id=406
24#define STATIC_SIMULATION_ISLAND_OPTIMIZATION 1
25
26struct  btElement
27{
28        int     m_id;
29        int     m_sz;
30};
31
32///UnionFind calculates connected subsets
33// Implements weighted Quick Union with path compression
34// optimization: could use short ints instead of ints (halving memory, would limit the number of rigid bodies to 64k, sounds reasonable)
35class btUnionFind
36  {
37    private:
38                btAlignedObjectArray<btElement> m_elements;
39
40    public:
41         
42                btUnionFind();
43                ~btUnionFind();
44
45       
46                //this is a special operation, destroying the content of btUnionFind.
47                //it sorts the elements, based on island id, in order to make it easy to iterate over islands
48                void    sortIslands();
49
50          void  reset(int N);
51
52          SIMD_FORCE_INLINE int getNumElements() const
53          {
54                  return int(m_elements.size());
55          }
56          SIMD_FORCE_INLINE bool  isRoot(int x) const
57          {
58                  return (x == m_elements[x].m_id);
59          }
60
61          btElement&    getElement(int index)
62          {
63                  return m_elements[index];
64          }
65          const btElement& getElement(int index) const
66          {
67                  return m_elements[index];
68          }
69   
70          void  allocate(int N);
71          void  Free();
72
73
74
75
76          int find(int p, int q)
77                { 
78                        return (find(p) == find(q)); 
79                }
80
81                void unite(int p, int q)
82                {
83                        int i = find(p), j = find(q);
84                        if (i == j) 
85                                return;
86
87#ifndef USE_PATH_COMPRESSION
88                        //weighted quick union, this keeps the 'trees' balanced, and keeps performance of unite O( log(n) )
89                        if (m_elements[i].m_sz < m_elements[j].m_sz)
90                        { 
91                                m_elements[i].m_id = j; m_elements[j].m_sz += m_elements[i].m_sz; 
92                        }
93                        else 
94                        { 
95                                m_elements[j].m_id = i; m_elements[i].m_sz += m_elements[j].m_sz; 
96                        }
97#else
98                        m_elements[i].m_id = j; m_elements[j].m_sz += m_elements[i].m_sz; 
99#endif //USE_PATH_COMPRESSION
100                }
101
102                int find(int x)
103                { 
104                        //btAssert(x < m_N);
105                        //btAssert(x >= 0);
106
107                        while (x != m_elements[x].m_id) 
108                        {
109                //not really a reason not to use path compression, and it flattens the trees/improves find performance dramatically
110       
111                #ifdef USE_PATH_COMPRESSION
112                                const btElement* elementPtr = &m_elements[m_elements[x].m_id];
113                                m_elements[x].m_id = elementPtr->m_id;
114                                x = elementPtr->m_id;                   
115                #else//
116                                x = m_elements[x].m_id;
117                #endif         
118                                //btAssert(x < m_N);
119                                //btAssert(x >= 0);
120
121                        }
122                        return x; 
123                }
124
125
126  };
127
128
129#endif //BT_UNION_FIND_H
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