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Diffstat (limited to 'extern/bullet2/src/BulletSoftBody/btConjugateGradient.h')
-rw-r--r-- | extern/bullet2/src/BulletSoftBody/btConjugateGradient.h | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/extern/bullet2/src/BulletSoftBody/btConjugateGradient.h b/extern/bullet2/src/BulletSoftBody/btConjugateGradient.h new file mode 100644 index 00000000000..bcd5e6b519d --- /dev/null +++ b/extern/bullet2/src/BulletSoftBody/btConjugateGradient.h @@ -0,0 +1,117 @@ +/* + Written by Xuchen Han <xuchenhan2015@u.northwestern.edu> + + Bullet Continuous Collision Detection and Physics Library + Copyright (c) 2019 Google Inc. http://bulletphysics.org + 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 BT_CONJUGATE_GRADIENT_H +#define BT_CONJUGATE_GRADIENT_H +#include "btKrylovSolver.h" +template <class MatrixX> +class btConjugateGradient : public btKrylovSolver<MatrixX> +{ + typedef btAlignedObjectArray<btVector3> TVStack; + typedef btKrylovSolver<MatrixX> Base; + TVStack r, p, z, temp; + +public: + btConjugateGradient(const int max_it_in) + : btKrylovSolver<MatrixX>(max_it_in, SIMD_EPSILON) + { + } + + virtual ~btConjugateGradient() {} + + // return the number of iterations taken + int solve(MatrixX& A, TVStack& x, const TVStack& b, bool verbose = false) + { + BT_PROFILE("CGSolve"); + btAssert(x.size() == b.size()); + reinitialize(b); + temp = b; + A.project(temp); + p = temp; + A.precondition(p, z); + btScalar d0 = this->dot(z, temp); + d0 = btMin(btScalar(1), d0); + // r = b - A * x --with assigned dof zeroed out + A.multiply(x, temp); + r = this->sub(b, temp); + A.project(r); + // z = M^(-1) * r + A.precondition(r, z); + A.project(z); + btScalar r_dot_z = this->dot(z, r); + if (r_dot_z <= Base::m_tolerance * d0) + { + if (verbose) + { + std::cout << "Iteration = 0" << std::endl; + std::cout << "Two norm of the residual = " << r_dot_z << std::endl; + } + return 0; + } + p = z; + btScalar r_dot_z_new = r_dot_z; + for (int k = 1; k <= Base::m_maxIterations; k++) + { + // temp = A*p + A.multiply(p, temp); + A.project(temp); + if (this->dot(p, temp) < 0) + { + if (verbose) + std::cout << "Encountered negative direction in CG!" << std::endl; + if (k == 1) + { + x = b; + } + return k; + } + // alpha = r^T * z / (p^T * A * p) + btScalar alpha = r_dot_z_new / this->dot(p, temp); + // x += alpha * p; + this->multAndAddTo(alpha, p, x); + // r -= alpha * temp; + this->multAndAddTo(-alpha, temp, r); + // z = M^(-1) * r + A.precondition(r, z); + r_dot_z = r_dot_z_new; + r_dot_z_new = this->dot(r, z); + if (r_dot_z_new < Base::m_tolerance * d0) + { + if (verbose) + { + std::cout << "ConjugateGradient iterations " << k << " residual = " << r_dot_z_new << std::endl; + } + return k; + } + + btScalar beta = r_dot_z_new / r_dot_z; + p = this->multAndAdd(beta, p, z); + } + if (verbose) + { + std::cout << "ConjugateGradient max iterations reached " << Base::m_maxIterations << " error = " << r_dot_z_new << std::endl; + } + return Base::m_maxIterations; + } + + void reinitialize(const TVStack& b) + { + r.resize(b.size()); + p.resize(b.size()); + z.resize(b.size()); + temp.resize(b.size()); + } +}; +#endif /* btConjugateGradient_h */ |