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      1 /*************************************************************************
      2  *                                                                       *
      3  * Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith.       *
      4  * All rights reserved.  Email: russ (at) q12.org   Web: www.q12.org          *
      5  *                                                                       *
      6  * This library is free software; you can redistribute it and/or         *
      7  * modify it under the terms of                                          *
      8  *   The BSD-style license that is included with this library in         *
      9  *   the file LICENSE-BSD.TXT.                                           *
     10  *                                                                       *
     11  * This library is distributed in the hope that it will be useful,       *
     12  * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
     13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    *
     14  * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     *
     15  *                                                                       *
     16  *************************************************************************/
     17 
     18 /*
     19 
     20 given (A,b,lo,hi), solve the LCP problem: A*x = b+w, where each x(i),w(i)
     21 satisfies one of
     22 	(1) x = lo, w >= 0
     23 	(2) x = hi, w <= 0
     24 	(3) lo < x < hi, w = 0
     25 A is a matrix of dimension n*n, everything else is a vector of size n*1.
     26 lo and hi can be +/- dInfinity as needed. the first `nub' variables are
     27 unbounded, i.e. hi and lo are assumed to be +/- dInfinity.
     28 
     29 we restrict lo(i) <= 0 and hi(i) >= 0.
     30 
     31 the original data (A,b) may be modified by this function.
     32 
     33 if the `findex' (friction index) parameter is nonzero, it points to an array
     34 of index values. in this case constraints that have findex[i] >= 0 are
     35 special. all non-special constraints are solved for, then the lo and hi values
     36 for the special constraints are set:
     37   hi[i] = abs( hi[i] * x[findex[i]] )
     38   lo[i] = -hi[i]
     39 and the solution continues. this mechanism allows a friction approximation
     40 to be implemented. the first `nub' variables are assumed to have findex < 0.
     41 
     42 */
     43 
     44 
     45 #ifndef _BT_LCP_H_
     46 #define _BT_LCP_H_
     47 
     48 #include <stdlib.h>
     49 #include <stdio.h>
     50 #include <assert.h>
     51 
     52 
     53 #include "LinearMath/btScalar.h"
     54 #include "LinearMath/btAlignedObjectArray.h"
     55 
     56 struct btDantzigScratchMemory
     57 {
     58 	btAlignedObjectArray<btScalar> m_scratch;
     59 	btAlignedObjectArray<btScalar> L;
     60 	btAlignedObjectArray<btScalar> d;
     61 	btAlignedObjectArray<btScalar> delta_w;
     62 	btAlignedObjectArray<btScalar> delta_x;
     63 	btAlignedObjectArray<btScalar> Dell;
     64 	btAlignedObjectArray<btScalar> ell;
     65 	btAlignedObjectArray<btScalar*> Arows;
     66 	btAlignedObjectArray<int> p;
     67 	btAlignedObjectArray<int> C;
     68 	btAlignedObjectArray<bool> state;
     69 };
     70 
     71 //return false if solving failed
     72 bool btSolveDantzigLCP (int n, btScalar *A, btScalar *x, btScalar *b, btScalar *w,
     73 	int nub, btScalar *lo, btScalar *hi, int *findex,btDantzigScratchMemory& scratch);
     74 
     75 
     76 
     77 #endif //_BT_LCP_H_
     78