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lib/haxebullet/bullet/BulletDynamics/MLCPSolvers/btSolveProjectedGaussSeidel.h

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+/*
+Bullet Continuous Collision Detection and Physics Library
+Copyright (c) 2003-2013 Erwin Coumans  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.
+*/
+///original version written by Erwin Coumans, October 2013
+
+#ifndef BT_SOLVE_PROJECTED_GAUSS_SEIDEL_H
+#define BT_SOLVE_PROJECTED_GAUSS_SEIDEL_H
+
+
+#include "btMLCPSolverInterface.h"
+
+///This solver is mainly for debug/learning purposes: it is functionally equivalent to the btSequentialImpulseConstraintSolver solver, but much slower (it builds the full LCP matrix)
+class btSolveProjectedGaussSeidel : public btMLCPSolverInterface
+{
+
+public:
+
+	btScalar m_leastSquaresResidualThreshold;
+	btScalar m_leastSquaresResidual;
+
+	btSolveProjectedGaussSeidel()
+		:m_leastSquaresResidualThreshold(0),
+		m_leastSquaresResidual(0)
+	{
+	}
+
+	virtual bool solveMLCP(const btMatrixXu & A, const btVectorXu & b, btVectorXu& x, const btVectorXu & lo,const btVectorXu & hi,const btAlignedObjectArray<int>& limitDependency, int numIterations, bool useSparsity = true)
+	{
+		if (!A.rows())
+			return true;
+		//the A matrix is sparse, so compute the non-zero elements
+		A.rowComputeNonZeroElements();
+
+		//A is a m-n matrix, m rows, n columns
+		btAssert(A.rows() == b.rows());
+
+		int i, j, numRows = A.rows();
+	
+		btScalar delta;
+
+		for (int k = 0; k <numIterations; k++)
+		{
+			m_leastSquaresResidual = 0.f;
+			for (i = 0; i <numRows; i++)
+			{
+				delta = 0.0f;
+				if (useSparsity)
+				{
+					for (int h=0;h<A.m_rowNonZeroElements1[i].size();h++)
+					{
+						int j = A.m_rowNonZeroElements1[i][h];
+						if (j != i)//skip main diagonal
+						{
+							delta += A(i,j) * x[j];
+						}
+					}
+				} else
+				{
+					for (j = 0; j <i; j++) 
+						delta += A(i,j) * x[j];
+					for (j = i+1; j<numRows; j++) 
+						delta += A(i,j) * x[j];
+				}
+
+				btScalar aDiag = A(i,i);
+				btScalar xOld = x[i];
+				x [i] = (b [i] - delta) / aDiag;
+				btScalar s = 1.f;
+
+				if (limitDependency[i]>=0)
+				{
+					s = x[limitDependency[i]];
+					if (s<0)
+						s=1;
+				}
+			
+				if (x[i]<lo[i]*s)
+					x[i]=lo[i]*s;
+				if (x[i]>hi[i]*s)
+					x[i]=hi[i]*s;
+				btScalar diff = x[i] - xOld;
+				m_leastSquaresResidual += diff*diff;
+			}
+
+			btScalar eps  = m_leastSquaresResidualThreshold;
+			if ((m_leastSquaresResidual < eps) || (k >=(numIterations-1)))
+			{
+#ifdef VERBOSE_PRINTF_RESIDUAL
+				printf("totalLenSqr = %f at iteration #%d\n", m_leastSquaresResidual,k);
+#endif
+				break;
+			}
+		}
+		return true;
+	}
+
+};
+
+#endif //BT_SOLVE_PROJECTED_GAUSS_SEIDEL_H