/home/coin/SVN-release/OS-2.0.1/Couenne/src/expression/operators/exprSum.cpp

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00001 /* $Id: exprSum.cpp 154 2009-06-16 18:52:53Z pbelotti $ */
00002 /*
00003  * Name:    exprSum.cpp
00004  * Author:  Pietro Belotti
00005  * Purpose: definition of sum expressions
00006  *
00007  * (C) Carnegie-Mellon University, 2006-07. 
00008  * This file is licensed under the Common Public License (CPL)
00009  */
00010 
00011 #include <stdlib.h>
00012 
00013 #include "exprSum.hpp"
00014 #include "exprCopy.hpp"
00015 #include "exprConst.hpp"
00016 
00017 
00019 exprSum::exprSum  (expression **al, int n): 
00020   exprOp (al, n) { //< non-leaf expression, with argument list
00021 
00022   if (al==NULL) {
00023     arglist_ = new expression * [1];
00024     *arglist_ = new exprConst (0);
00025     nargs_ = 1;    
00026   }
00027 
00028   // commutative operator, sort elements
00029   if (nargs_ > 1)
00030     qsort (arglist_, nargs_, sizeof (expression*), compareExpr);
00031 }
00032 
00033 
00035 exprSum::exprSum (expression *arg0, expression *arg1):
00036   exprOp (arg0, arg1) {
00037 
00038   //  qsort (arglist_, nargs_, sizeof (expression*), compareExpr); // useless...
00039 
00040   if (arg0 -> compare (*arg1) > 0) { // swap elements
00041     expression *swap = arglist_ [0];
00042     arglist_ [0] = arglist_ [1];
00043     arglist_ [1] = swap;
00044   }
00045 }
00046 
00047 
00049 
00050 expression *exprSum::simplify () {
00051 
00052   exprOp:: simplify ();
00053 
00054   if (nargs_ == 1) {
00055 
00056     expression *ret = arglist_ [0];
00057     arglist_ [0] = NULL;
00058     return ret;
00059   }
00060 
00061   // from here on we assume the operands have been simplified
00062 
00063   CouNumber total     = 0;
00064   bool      found_one = false;
00065 
00066   for (register int i=0; i<nargs_; i++) {
00067 
00068     // check for constant operands in multiplications
00069 
00070     if (arglist_ [i] -> Type () == CONST) {
00071 
00072       total += arglist_ [i] -> Value ();
00073       found_one = true;
00074       delete arglist_ [i]; 
00075       arglist_ [i] = NULL;
00076     }
00077   }
00078 
00079   /*
00080   if (found_one && shrink_arglist (total, 0))
00081     return new exprConst (arglist_ [0] -> Value ());
00082   else return NULL;
00083   */
00084 
00085   if (found_one && shrink_arglist (total, 0)) {
00086     expression *ret = arglist_ [0];
00087     arglist_ [0] = NULL;
00088     return ret;
00089   }
00090   else return NULL;
00091 }
00092 
00093 
00095 
00096 expression *exprSum:: differentiate (int index) {
00097 
00098   //  exprOp::differentiate (index); // FIX IT: why is it called?
00099 
00100   expression **arglist = new expression * [nargs_];
00101 
00102   register int nonconst = 0;
00103 
00104   for (int i = 0; i < nargs_; i++) 
00105     if (arglist_ [i] -> dependsOn (index))
00106       arglist [nonconst++] = arglist_ [i] -> differentiate (index);
00107 
00108   if (!nonconst) {
00109     delete [] arglist;
00110     return new exprConst (0.);
00111   }
00112   else return new exprSum (arglist, nonconst);
00113 }
00114 
00115 
00117 void exprSum::getBounds (expression *&lb, expression *&ub) {
00118 
00119   expression **all = new expression * [nargs_];
00120   expression **alu = new expression * [nargs_];
00121 
00122   for (int i=0; i<nargs_; i++)
00123     arglist_ [i] -> getBounds (all [i], alu [i]);
00124 
00125   lb = new exprSum (all, nargs_);
00126   ub = new exprSum (alu, nargs_);
00127 }
00128 
00129 
00131 void exprSum::getBounds (CouNumber &lb, CouNumber &ub) {
00132 
00133   CouNumber tlb, tub;
00134 
00135   lb = ub = 0;
00136 
00137   for (int i=0; i<nargs_; i++) {
00138     arglist_ [i] -> getBounds (tlb, tub);
00139     lb += tlb;
00140     ub += tub;
00141   }
00142 }
00143 
00144 
00146 int exprSum::Linearity () {
00147 
00148   int linmax = arglist_ [0] -> Linearity ();
00149 
00150   for (register int i=1; i<nargs_; i++) {
00151     register int lin = arglist_ [i] -> Linearity ();
00152     if (lin > linmax) linmax = lin;
00153   }
00154   return linmax;
00155 }

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