Bullet Collision Detection & Physics Library: btConjugateResidual.h Source File

Bullet Collision Detection & Physics Library

btConjugateResidual.h
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1/*
2 Written by Xuchen Han <xuchenhan2015@u.northwestern.edu>
3
4 Bullet Continuous Collision Detection and Physics Library
5 Copyright (c) 2019 Google Inc. http://bulletphysics.org
6 This software is provided 'as-is', without any express or implied warranty.
7 In no event will the authors be held liable for any damages arising from the use of this software.
8 Permission is granted to anyone to use this software for any purpose,
9 including commercial applications, and to alter it and redistribute it freely,
10 subject to the following restrictions:
11 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.
12 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
13 3. This notice may not be removed or altered from any source distribution.
14 */
15
16#ifndef BT_CONJUGATE_RESIDUAL_H
17#define BT_CONJUGATE_RESIDUAL_H
18#include "btKrylovSolver.h"
19
20template <class MatrixX>
21 class btConjugateResidual : public btKrylovSolver<MatrixX>
22{
23 typedef btAlignedObjectArray<btVector3> TVStack;
24 typedef btKrylovSolver<MatrixX> Base;
25 TVStack r, p, z, temp_p, temp_r, best_x;
26 // temp_r = A*r
27 // temp_p = A*p
28 // z = M^(-1) * temp_p = M^(-1) * A * p
29 btScalar best_r;
30
31public:
32 btConjugateResidual(const int max_it_in)
33 : Base(max_it_in, 1e-8)
34 {
35 }
36
37 virtual ~btConjugateResidual() {}
38
39 // return the number of iterations taken
40 int solve(MatrixX& A, TVStack& x, const TVStack& b, bool verbose = false)
41 {
42 BT_PROFILE("CRSolve");
43 btAssert(x.size() == b.size());
44 reinitialize(b);
45 // r = b - A * x --with assigned dof zeroed out
46 A.multiply(x, temp_r); // borrow temp_r here to store A*x
47 r = this->sub(b, temp_r);
48 // z = M^(-1) * r
49 A.precondition(r, z); // borrow z to store preconditioned r
50 r = z;
51 btScalar residual_norm = this->norm(r);
52 if (residual_norm <= Base::m_tolerance)
53 {
54 return 0;
55 }
56 p = r;
57 btScalar r_dot_Ar, r_dot_Ar_new;
58 // temp_p = A*p
59 A.multiply(p, temp_p);
60 // temp_r = A*r
61 temp_r = temp_p;
62 r_dot_Ar = this->dot(r, temp_r);
63 for (int k = 1; k <= Base::m_maxIterations; k++)
64 {
65 // z = M^(-1) * Ap
66 A.precondition(temp_p, z);
67 // alpha = r^T * A * r / (Ap)^T * M^-1 * Ap)
68 btScalar alpha = r_dot_Ar / this->dot(temp_p, z);
69 // x += alpha * p;
70 this->multAndAddTo(alpha, p, x);
71 // r -= alpha * z;
72 this->multAndAddTo(-alpha, z, r);
73 btScalar norm_r = this->norm(r);
74 if (norm_r < best_r)
75 {
76 best_x = x;
77 best_r = norm_r;
78 if (norm_r < Base::m_tolerance)
79 {
80 return k;
81 }
82 }
83 // temp_r = A * r;
84 A.multiply(r, temp_r);
85 r_dot_Ar_new = this->dot(r, temp_r);
86 btScalar beta = r_dot_Ar_new / r_dot_Ar;
87 r_dot_Ar = r_dot_Ar_new;
88 // p = beta*p + r;
89 p = this->multAndAdd(beta, p, r);
90 // temp_p = beta*temp_p + temp_r;
91 temp_p = this->multAndAdd(beta, temp_p, temp_r);
92 }
93 if (verbose)
94 {
95 std::cout << "ConjugateResidual max iterations reached, residual = " << best_r << std::endl;
96 }
97 x = best_x;
98 return Base::m_maxIterations;
99 }
100
101 void reinitialize(const TVStack& b)
102 {
103 r.resize(b.size());
104 p.resize(b.size());
105 z.resize(b.size());
106 temp_p.resize(b.size());
107 temp_r.resize(b.size());
108 best_x.resize(b.size());
109 best_r = SIMD_INFINITY;
110 }
111};
112#endif /* btConjugateResidual_h */
btKrylovSolver.h
BT_PROFILE
#define BT_PROFILE(name)
Definition btQuickprof.h:198
btScalar
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition btScalar.h:314
SIMD_INFINITY
#define SIMD_INFINITY
Definition btScalar.h:544
btAssert
#define btAssert(x)
Definition btScalar.h:153
btAlignedObjectArray
The btAlignedObjectArray template class uses a subset of the stl::vector interface for its methods It...
Definition btAlignedObjectArray.h:46
btAlignedObjectArray::size
int size() const
return the number of elements in the array
Definition btAlignedObjectArray.h:142
btConjugateResidual::best_r
btScalar best_r
Definition btConjugateResidual.h:29
btConjugateResidual::btConjugateResidual
btConjugateResidual(const int max_it_in)
Definition btConjugateResidual.h:32
btConjugateResidual::solve
int solve(MatrixX &A, TVStack &x, const TVStack &b, bool verbose=false)
Definition btConjugateResidual.h:40
btConjugateResidual::reinitialize
void reinitialize(const TVStack &b)
Definition btConjugateResidual.h:101
btConjugateResidual::Base
btKrylovSolver< MatrixX > Base
Definition btConjugateResidual.h:24
btConjugateResidual::z
TVStack z
Definition btConjugateResidual.h:25
btConjugateResidual::r
TVStack r
Definition btConjugateResidual.h:25
btConjugateResidual::~btConjugateResidual
virtual ~btConjugateResidual()
Definition btConjugateResidual.h:37
btConjugateResidual::p
TVStack p
Definition btConjugateResidual.h:25
btConjugateResidual::best_x
TVStack best_x
Definition btConjugateResidual.h:25
btConjugateResidual::TVStack
btAlignedObjectArray< btVector3 > TVStack
Definition btConjugateResidual.h:23
btConjugateResidual::temp_p
TVStack temp_p
Definition btConjugateResidual.h:25
btConjugateResidual::temp_r
TVStack temp_r
Definition btConjugateResidual.h:25
btKrylovSolver::norm
virtual btScalar norm(const TVStack &a)
Definition btKrylovSolver.h:63
btKrylovSolver::dot
virtual btScalar dot(const TVStack &a, const TVStack &b)
Definition btKrylovSolver.h:76
btKrylovSolver::sub
virtual TVStack sub(const TVStack &a, const TVStack &b)
Definition btKrylovSolver.h:45
btKrylovSolver::m_tolerance
btScalar m_tolerance
Definition btKrylovSolver.h:33
btKrylovSolver::btKrylovSolver
btKrylovSolver(int maxIterations, btScalar tolerance)
Definition btKrylovSolver.h:34
btKrylovSolver::multAndAddTo
virtual void multAndAddTo(btScalar s, const TVStack &a, TVStack &result)
Definition btKrylovSolver.h:84
btKrylovSolver::m_maxIterations
int m_maxIterations
Definition btKrylovSolver.h:32
btKrylovSolver::multAndAdd
virtual TVStack multAndAdd(btScalar s, const TVStack &a, const TVStack &b)
Definition btKrylovSolver.h:92