source: trunk/sources/ALGLIB/dforest.cs @ 2636

/*************************************************************************
Copyright (c) 2009, Sergey Bochkanov (ALGLIB project).

>>> SOURCE LICENSE >>>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation (www.fsf.org); either version 2 of the 
License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

A copy of the GNU General Public License is available at
http://www.fsf.org/licensing/licenses

>>> END OF LICENSE >>>
*************************************************************************/

using System;

namespace alglib
{
    public class dforest
    {
        public struct decisionforest
        {
            public int nvars;
            public int nclasses;
            public int ntrees;
            public int bufsize;
            public double[] trees;
        };


        public struct dfreport
        {
            public double relclserror;
            public double avgce;
            public double rmserror;
            public double avgerror;
            public double avgrelerror;
            public double oobrelclserror;
            public double oobavgce;
            public double oobrmserror;
            public double oobavgerror;
            public double oobavgrelerror;
        };


        public struct dfinternalbuffers
        {
            public double[] treebuf;
            public int[] idxbuf;
            public double[] tmpbufr;
            public double[] tmpbufr2;
            public int[] tmpbufi;
            public int[] classibuf;
            public int[] varpool;
            public bool[] evsbin;
            public double[] evssplits;
        };




        public const int dfvnum = 8;
        public const int innernodewidth = 3;
        public const int leafnodewidth = 2;
        public const int dfusestrongsplits = 1;
        public const int dfuseevs = 2;


        /*************************************************************************
        This subroutine builds random decision forest.

        INPUT PARAMETERS:
            XY          -   training set
            NPoints     -   training set size, NPoints>=1
            NVars       -   number of independent variables, NVars>=1
            NClasses    -   task type:
                            * NClasses=1 - regression task with one
                                           dependent variable
                            * NClasses>1 - classification task with
                                           NClasses classes.
            NTrees      -   number of trees in a forest, NTrees>=1.
                            recommended values: 50-100.
            R           -   percent of a training set used to build
                            individual trees. 0<R<=1.
                            recommended values: 0.1 <= R <= 0.66.

        OUTPUT PARAMETERS:
            Info        -   return code:
                            * -2, if there is a point with class number
                                  outside of [0..NClasses-1].
                            * -1, if incorrect parameters was passed
                                  (NPoints<1, NVars<1, NClasses<1, NTrees<1, R<=0
                                  or R>1).
                            *  1, if task has been solved
            DF          -   model built
            Rep         -   training report, contains error on a training set
                            and out-of-bag estimates of generalization error.

          -- ALGLIB --
             Copyright 19.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static void dfbuildrandomdecisionforest(ref double[,] xy,
            int npoints,
            int nvars,
            int nclasses,
            int ntrees,
            double r,
            ref int info,
            ref decisionforest df,
            ref dfreport rep)
        {
            int samplesize = 0;

            if( (double)(r)<=(double)(0) | (double)(r)>(double)(1) )
            {
                info = -1;
                return;
            }
            samplesize = Math.Max((int)Math.Round(r*npoints), 1);
            dfbuildinternal(ref xy, npoints, nvars, nclasses, ntrees, samplesize, Math.Max(nvars/2, 1), dfusestrongsplits+dfuseevs, ref info, ref df, ref rep);
        }


        public static void dfbuildinternal(ref double[,] xy,
            int npoints,
            int nvars,
            int nclasses,
            int ntrees,
            int samplesize,
            int nfeatures,
            int flags,
            ref int info,
            ref decisionforest df,
            ref dfreport rep)
        {
            int i = 0;
            int j = 0;
            int k = 0;
            int tmpi = 0;
            int lasttreeoffs = 0;
            int offs = 0;
            int ooboffs = 0;
            int treesize = 0;
            int nvarsinpool = 0;
            bool useevs = new bool();
            dfinternalbuffers bufs = new dfinternalbuffers();
            int[] permbuf = new int[0];
            double[] oobbuf = new double[0];
            int[] oobcntbuf = new int[0];
            double[,] xys = new double[0,0];
            double[] x = new double[0];
            double[] y = new double[0];
            int oobcnt = 0;
            int oobrelcnt = 0;
            double v = 0;
            double vmin = 0;
            double vmax = 0;
            bool bflag = new bool();
            int i_ = 0;
            int i1_ = 0;

            
            //
            // Test for inputs
            //
            if( npoints<1 | samplesize<1 | samplesize>npoints | nvars<1 | nclasses<1 | ntrees<1 | nfeatures<1 )
            {
                info = -1;
                return;
            }
            if( nclasses>1 )
            {
                for(i=0; i<=npoints-1; i++)
                {
                    if( (int)Math.Round(xy[i,nvars])<0 | (int)Math.Round(xy[i,nvars])>=nclasses )
                    {
                        info = -2;
                        return;
                    }
                }
            }
            info = 1;
            
            //
            // Flags
            //
            useevs = flags/dfuseevs%2!=0;
            
            //
            // Allocate data, prepare header
            //
            treesize = 1+innernodewidth*(samplesize-1)+leafnodewidth*samplesize;
            permbuf = new int[npoints-1+1];
            bufs.treebuf = new double[treesize-1+1];
            bufs.idxbuf = new int[npoints-1+1];
            bufs.tmpbufr = new double[npoints-1+1];
            bufs.tmpbufr2 = new double[npoints-1+1];
            bufs.tmpbufi = new int[npoints-1+1];
            bufs.varpool = new int[nvars-1+1];
            bufs.evsbin = new bool[nvars-1+1];
            bufs.evssplits = new double[nvars-1+1];
            bufs.classibuf = new int[2*nclasses-1+1];
            oobbuf = new double[nclasses*npoints-1+1];
            oobcntbuf = new int[npoints-1+1];
            df.trees = new double[ntrees*treesize-1+1];
            xys = new double[samplesize-1+1, nvars+1];
            x = new double[nvars-1+1];
            y = new double[nclasses-1+1];
            for(i=0; i<=npoints-1; i++)
            {
                permbuf[i] = i;
            }
            for(i=0; i<=npoints*nclasses-1; i++)
            {
                oobbuf[i] = 0;
            }
            for(i=0; i<=npoints-1; i++)
            {
                oobcntbuf[i] = 0;
            }
            
            //
            // Prepare variable pool and EVS (extended variable selection/splitting) buffers
            // (whether EVS is turned on or not):
            // 1. detect binary variables and pre-calculate splits for them
            // 2. detect variables with non-distinct values and exclude them from pool
            //
            for(i=0; i<=nvars-1; i++)
            {
                bufs.varpool[i] = i;
            }
            nvarsinpool = nvars;
            if( useevs )
            {
                for(j=0; j<=nvars-1; j++)
                {
                    vmin = xy[0,j];
                    vmax = vmin;
                    for(i=0; i<=npoints-1; i++)
                    {
                        v = xy[i,j];
                        vmin = Math.Min(vmin, v);
                        vmax = Math.Max(vmax, v);
                    }
                    if( (double)(vmin)==(double)(vmax) )
                    {
                        
                        //
                        // exclude variable from pool
                        //
                        bufs.varpool[j] = bufs.varpool[nvarsinpool-1];
                        bufs.varpool[nvarsinpool-1] = -1;
                        nvarsinpool = nvarsinpool-1;
                        continue;
                    }
                    bflag = false;
                    for(i=0; i<=npoints-1; i++)
                    {
                        v = xy[i,j];
                        if( (double)(v)!=(double)(vmin) & (double)(v)!=(double)(vmax) )
                        {
                            bflag = true;
                            break;
                        }
                    }
                    if( bflag )
                    {
                        
                        //
                        // non-binary variable
                        //
                        bufs.evsbin[j] = false;
                    }
                    else
                    {
                        
                        //
                        // Prepare
                        //
                        bufs.evsbin[j] = true;
                        bufs.evssplits[j] = 0.5*(vmin+vmax);
                        if( (double)(bufs.evssplits[j])<=(double)(vmin) )
                        {
                            bufs.evssplits[j] = vmax;
                        }
                    }
                }
            }
            
            //
            // RANDOM FOREST FORMAT
            // W[0]         -   size of array
            // W[1]         -   version number
            // W[2]         -   NVars
            // W[3]         -   NClasses (1 for regression)
            // W[4]         -   NTrees
            // W[5]         -   trees offset
            //
            //
            // TREE FORMAT
            // W[Offs]      -   size of sub-array
            //     node info:
            // W[K+0]       -   variable number        (-1 for leaf mode)
            // W[K+1]       -   threshold              (class/value for leaf node)
            // W[K+2]       -   ">=" branch index      (absent for leaf node)
            //
            //
            df.nvars = nvars;
            df.nclasses = nclasses;
            df.ntrees = ntrees;
            
            //
            // Build forest
            //
            offs = 0;
            for(i=0; i<=ntrees-1; i++)
            {
                
                //
                // Prepare sample
                //
                for(k=0; k<=samplesize-1; k++)
                {
                    j = k+AP.Math.RandomInteger(npoints-k);
                    tmpi = permbuf[k];
                    permbuf[k] = permbuf[j];
                    permbuf[j] = tmpi;
                    j = permbuf[k];
                    for(i_=0; i_<=nvars;i_++)
                    {
                        xys[k,i_] = xy[j,i_];
                    }
                }
                
                //
                // build tree, copy
                //
                dfbuildtree(ref xys, samplesize, nvars, nclasses, nfeatures, nvarsinpool, flags, ref bufs);
                j = (int)Math.Round(bufs.treebuf[0]);
                i1_ = (0) - (offs);
                for(i_=offs; i_<=offs+j-1;i_++)
                {
                    df.trees[i_] = bufs.treebuf[i_+i1_];
                }
                lasttreeoffs = offs;
                offs = offs+j;
                
                //
                // OOB estimates
                //
                for(k=samplesize; k<=npoints-1; k++)
                {
                    for(j=0; j<=nclasses-1; j++)
                    {
                        y[j] = 0;
                    }
                    j = permbuf[k];
                    for(i_=0; i_<=nvars-1;i_++)
                    {
                        x[i_] = xy[j,i_];
                    }
                    dfprocessinternal(ref df, lasttreeoffs, ref x, ref y);
                    i1_ = (0) - (j*nclasses);
                    for(i_=j*nclasses; i_<=(j+1)*nclasses-1;i_++)
                    {
                        oobbuf[i_] = oobbuf[i_] + y[i_+i1_];
                    }
                    oobcntbuf[j] = oobcntbuf[j]+1;
                }
            }
            df.bufsize = offs;
            
            //
            // Normalize OOB results
            //
            for(i=0; i<=npoints-1; i++)
            {
                if( oobcntbuf[i]!=0 )
                {
                    v = (double)(1)/(double)(oobcntbuf[i]);
                    for(i_=i*nclasses; i_<=i*nclasses+nclasses-1;i_++)
                    {
                        oobbuf[i_] = v*oobbuf[i_];
                    }
                }
            }
            
            //
            // Calculate training set estimates
            //
            rep.relclserror = dfrelclserror(ref df, ref xy, npoints);
            rep.avgce = dfavgce(ref df, ref xy, npoints);
            rep.rmserror = dfrmserror(ref df, ref xy, npoints);
            rep.avgerror = dfavgerror(ref df, ref xy, npoints);
            rep.avgrelerror = dfavgrelerror(ref df, ref xy, npoints);
            
            //
            // Calculate OOB estimates.
            //
            rep.oobrelclserror = 0;
            rep.oobavgce = 0;
            rep.oobrmserror = 0;
            rep.oobavgerror = 0;
            rep.oobavgrelerror = 0;
            oobcnt = 0;
            oobrelcnt = 0;
            for(i=0; i<=npoints-1; i++)
            {
                if( oobcntbuf[i]!=0 )
                {
                    ooboffs = i*nclasses;
                    if( nclasses>1 )
                    {
                        
                        //
                        // classification-specific code
                        //
                        k = (int)Math.Round(xy[i,nvars]);
                        tmpi = 0;
                        for(j=1; j<=nclasses-1; j++)
                        {
                            if( (double)(oobbuf[ooboffs+j])>(double)(oobbuf[ooboffs+tmpi]) )
                            {
                                tmpi = j;
                            }
                        }
                        if( tmpi!=k )
                        {
                            rep.oobrelclserror = rep.oobrelclserror+1;
                        }
                        if( (double)(oobbuf[ooboffs+k])!=(double)(0) )
                        {
                            rep.oobavgce = rep.oobavgce-Math.Log(oobbuf[ooboffs+k]);
                        }
                        else
                        {
                            rep.oobavgce = rep.oobavgce-Math.Log(AP.Math.MinRealNumber);
                        }
                        for(j=0; j<=nclasses-1; j++)
                        {
                            if( j==k )
                            {
                                rep.oobrmserror = rep.oobrmserror+AP.Math.Sqr(oobbuf[ooboffs+j]-1);
                                rep.oobavgerror = rep.oobavgerror+Math.Abs(oobbuf[ooboffs+j]-1);
                                rep.oobavgrelerror = rep.oobavgrelerror+Math.Abs(oobbuf[ooboffs+j]-1);
                                oobrelcnt = oobrelcnt+1;
                            }
                            else
                            {
                                rep.oobrmserror = rep.oobrmserror+AP.Math.Sqr(oobbuf[ooboffs+j]);
                                rep.oobavgerror = rep.oobavgerror+Math.Abs(oobbuf[ooboffs+j]);
                            }
                        }
                    }
                    else
                    {
                        
                        //
                        // regression-specific code
                        //
                        rep.oobrmserror = rep.oobrmserror+AP.Math.Sqr(oobbuf[ooboffs]-xy[i,nvars]);
                        rep.oobavgerror = rep.oobavgerror+Math.Abs(oobbuf[ooboffs]-xy[i,nvars]);
                        if( (double)(xy[i,nvars])!=(double)(0) )
                        {
                            rep.oobavgrelerror = rep.oobavgrelerror+Math.Abs((oobbuf[ooboffs]-xy[i,nvars])/xy[i,nvars]);
                            oobrelcnt = oobrelcnt+1;
                        }
                    }
                    
                    //
                    // update OOB estimates count.
                    //
                    oobcnt = oobcnt+1;
                }
            }
            if( oobcnt>0 )
            {
                rep.oobrelclserror = rep.oobrelclserror/oobcnt;
                rep.oobavgce = rep.oobavgce/oobcnt;
                rep.oobrmserror = Math.Sqrt(rep.oobrmserror/(oobcnt*nclasses));
                rep.oobavgerror = rep.oobavgerror/(oobcnt*nclasses);
                if( oobrelcnt>0 )
                {
                    rep.oobavgrelerror = rep.oobavgrelerror/oobrelcnt;
                }
            }
        }


        /*************************************************************************
        Procesing

        INPUT PARAMETERS:
            DF      -   decision forest model
            X       -   input vector,  array[0..NVars-1].

        OUTPUT PARAMETERS:
            Y       -   result. Regression estimate when solving regression  task,
                        vector of posterior probabilities for classification task.
                        Subroutine does not allocate memory for this vector, it is
                        responsibility of a caller to allocate it. Array  must  be
                        at least [0..NClasses-1].

          -- ALGLIB --
             Copyright 16.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static void dfprocess(ref decisionforest df,
            ref double[] x,
            ref double[] y)
        {
            int offs = 0;
            int i = 0;
            double v = 0;
            int i_ = 0;

            
            //
            // Proceed
            //
            offs = 0;
            for(i=0; i<=df.nclasses-1; i++)
            {
                y[i] = 0;
            }
            for(i=0; i<=df.ntrees-1; i++)
            {
                
                //
                // Process basic tree
                //
                dfprocessinternal(ref df, offs, ref x, ref y);
                
                //
                // Next tree
                //
                offs = offs+(int)Math.Round(df.trees[offs]);
            }
            v = (double)(1)/(double)(df.ntrees);
            for(i_=0; i_<=df.nclasses-1;i_++)
            {
                y[i_] = v*y[i_];
            }
        }


        /*************************************************************************
        Relative classification error on the test set

        INPUT PARAMETERS:
            DF      -   decision forest model
            XY      -   test set
            NPoints -   test set size

        RESULT:
            percent of incorrectly classified cases.
            Zero if model solves regression task.

          -- ALGLIB --
             Copyright 16.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static double dfrelclserror(ref decisionforest df,
            ref double[,] xy,
            int npoints)
        {
            double result = 0;

            result = (double)(dfclserror(ref df, ref xy, npoints))/(double)(npoints);
            return result;
        }


        /*************************************************************************
        Average cross-entropy (in bits per element) on the test set

        INPUT PARAMETERS:
            DF      -   decision forest model
            XY      -   test set
            NPoints -   test set size

        RESULT:
            CrossEntropy/(NPoints*LN(2)).
            Zero if model solves regression task.

          -- ALGLIB --
             Copyright 16.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static double dfavgce(ref decisionforest df,
            ref double[,] xy,
            int npoints)
        {
            double result = 0;
            double[] x = new double[0];
            double[] y = new double[0];
            int i = 0;
            int j = 0;
            int k = 0;
            int tmpi = 0;
            int i_ = 0;

            x = new double[df.nvars-1+1];
            y = new double[df.nclasses-1+1];
            result = 0;
            for(i=0; i<=npoints-1; i++)
            {
                for(i_=0; i_<=df.nvars-1;i_++)
                {
                    x[i_] = xy[i,i_];
                }
                dfprocess(ref df, ref x, ref y);
                if( df.nclasses>1 )
                {
                    
                    //
                    // classification-specific code
                    //
                    k = (int)Math.Round(xy[i,df.nvars]);
                    tmpi = 0;
                    for(j=1; j<=df.nclasses-1; j++)
                    {
                        if( (double)(y[j])>(double)(y[tmpi]) )
                        {
                            tmpi = j;
                        }
                    }
                    if( (double)(y[k])!=(double)(0) )
                    {
                        result = result-Math.Log(y[k]);
                    }
                    else
                    {
                        result = result-Math.Log(AP.Math.MinRealNumber);
                    }
                }
            }
            result = result/npoints;
            return result;
        }


        /*************************************************************************
        RMS error on the test set

        INPUT PARAMETERS:
            DF      -   decision forest model
            XY      -   test set
            NPoints -   test set size

        RESULT:
            root mean square error.
            Its meaning for regression task is obvious. As for
            classification task, RMS error means error when estimating posterior
            probabilities.

          -- ALGLIB --
             Copyright 16.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static double dfrmserror(ref decisionforest df,
            ref double[,] xy,
            int npoints)
        {
            double result = 0;
            double[] x = new double[0];
            double[] y = new double[0];
            int i = 0;
            int j = 0;
            int k = 0;
            int tmpi = 0;
            int i_ = 0;

            x = new double[df.nvars-1+1];
            y = new double[df.nclasses-1+1];
            result = 0;
            for(i=0; i<=npoints-1; i++)
            {
                for(i_=0; i_<=df.nvars-1;i_++)
                {
                    x[i_] = xy[i,i_];
                }
                dfprocess(ref df, ref x, ref y);
                if( df.nclasses>1 )
                {
                    
                    //
                    // classification-specific code
                    //
                    k = (int)Math.Round(xy[i,df.nvars]);
                    tmpi = 0;
                    for(j=1; j<=df.nclasses-1; j++)
                    {
                        if( (double)(y[j])>(double)(y[tmpi]) )
                        {
                            tmpi = j;
                        }
                    }
                    for(j=0; j<=df.nclasses-1; j++)
                    {
                        if( j==k )
                        {
                            result = result+AP.Math.Sqr(y[j]-1);
                        }
                        else
                        {
                            result = result+AP.Math.Sqr(y[j]);
                        }
                    }
                }
                else
                {
                    
                    //
                    // regression-specific code
                    //
                    result = result+AP.Math.Sqr(y[0]-xy[i,df.nvars]);
                }
            }
            result = Math.Sqrt(result/(npoints*df.nclasses));
            return result;
        }


        /*************************************************************************
        Average error on the test set

        INPUT PARAMETERS:
            DF      -   decision forest model
            XY      -   test set
            NPoints -   test set size

        RESULT:
            Its meaning for regression task is obvious. As for
            classification task, it means average error when estimating posterior
            probabilities.

          -- ALGLIB --
             Copyright 16.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static double dfavgerror(ref decisionforest df,
            ref double[,] xy,
            int npoints)
        {
            double result = 0;
            double[] x = new double[0];
            double[] y = new double[0];
            int i = 0;
            int j = 0;
            int k = 0;
            int i_ = 0;

            x = new double[df.nvars-1+1];
            y = new double[df.nclasses-1+1];
            result = 0;
            for(i=0; i<=npoints-1; i++)
            {
                for(i_=0; i_<=df.nvars-1;i_++)
                {
                    x[i_] = xy[i,i_];
                }
                dfprocess(ref df, ref x, ref y);
                if( df.nclasses>1 )
                {
                    
                    //
                    // classification-specific code
                    //
                    k = (int)Math.Round(xy[i,df.nvars]);
                    for(j=0; j<=df.nclasses-1; j++)
                    {
                        if( j==k )
                        {
                            result = result+Math.Abs(y[j]-1);
                        }
                        else
                        {
                            result = result+Math.Abs(y[j]);
                        }
                    }
                }
                else
                {
                    
                    //
                    // regression-specific code
                    //
                    result = result+Math.Abs(y[0]-xy[i,df.nvars]);
                }
            }
            result = result/(npoints*df.nclasses);
            return result;
        }


        /*************************************************************************
        Average relative error on the test set

        INPUT PARAMETERS:
            DF      -   decision forest model
            XY      -   test set
            NPoints -   test set size

        RESULT:
            Its meaning for regression task is obvious. As for
            classification task, it means average relative error when estimating
            posterior probability of belonging to the correct class.

          -- ALGLIB --
             Copyright 16.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static double dfavgrelerror(ref decisionforest df,
            ref double[,] xy,
            int npoints)
        {
            double result = 0;
            double[] x = new double[0];
            double[] y = new double[0];
            int relcnt = 0;
            int i = 0;
            int j = 0;
            int k = 0;
            int i_ = 0;

            x = new double[df.nvars-1+1];
            y = new double[df.nclasses-1+1];
            result = 0;
            relcnt = 0;
            for(i=0; i<=npoints-1; i++)
            {
                for(i_=0; i_<=df.nvars-1;i_++)
                {
                    x[i_] = xy[i,i_];
                }
                dfprocess(ref df, ref x, ref y);
                if( df.nclasses>1 )
                {
                    
                    //
                    // classification-specific code
                    //
                    k = (int)Math.Round(xy[i,df.nvars]);
                    for(j=0; j<=df.nclasses-1; j++)
                    {
                        if( j==k )
                        {
                            result = result+Math.Abs(y[j]-1);
                            relcnt = relcnt+1;
                        }
                    }
                }
                else
                {
                    
                    //
                    // regression-specific code
                    //
                    if( (double)(xy[i,df.nvars])!=(double)(0) )
                    {
                        result = result+Math.Abs((y[0]-xy[i,df.nvars])/xy[i,df.nvars]);
                        relcnt = relcnt+1;
                    }
                }
            }
            if( relcnt>0 )
            {
                result = result/relcnt;
            }
            return result;
        }


        /*************************************************************************
        Copying of DecisionForest strucure

        INPUT PARAMETERS:
            DF1 -   original

        OUTPUT PARAMETERS:
            DF2 -   copy

          -- ALGLIB --
             Copyright 13.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static void dfcopy(ref decisionforest df1,
            ref decisionforest df2)
        {
            int i_ = 0;

            df2.nvars = df1.nvars;
            df2.nclasses = df1.nclasses;
            df2.ntrees = df1.ntrees;
            df2.bufsize = df1.bufsize;
            df2.trees = new double[df1.bufsize-1+1];
            for(i_=0; i_<=df1.bufsize-1;i_++)
            {
                df2.trees[i_] = df1.trees[i_];
            }
        }


        /*************************************************************************
        Serialization of DecisionForest strucure

        INPUT PARAMETERS:
            DF      -   original

        OUTPUT PARAMETERS:
            RA      -   array of real numbers which stores decision forest,
                        array[0..RLen-1]
            RLen    -   RA lenght

          -- ALGLIB --
             Copyright 13.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static void dfserialize(ref decisionforest df,
            ref double[] ra,
            ref int rlen)
        {
            int i_ = 0;
            int i1_ = 0;

            ra = new double[df.bufsize+5-1+1];
            ra[0] = dfvnum;
            ra[1] = df.nvars;
            ra[2] = df.nclasses;
            ra[3] = df.ntrees;
            ra[4] = df.bufsize;
            i1_ = (0) - (5);
            for(i_=5; i_<=5+df.bufsize-1;i_++)
            {
                ra[i_] = df.trees[i_+i1_];
            }
            rlen = 5+df.bufsize;
        }


        /*************************************************************************
        Unserialization of DecisionForest strucure

        INPUT PARAMETERS:
            RA      -   real array which stores decision forest

        OUTPUT PARAMETERS:
            DF      -   restored structure

          -- ALGLIB --
             Copyright 13.02.2009 by Bochkanov Sergey
        *************************************************************************/
        public static void dfunserialize(ref double[] ra,
            ref decisionforest df)
        {
            int i_ = 0;
            int i1_ = 0;

            System.Diagnostics.Debug.Assert((int)Math.Round(ra[0])==dfvnum, "DFUnserialize: incorrect array!");
            df.nvars = (int)Math.Round(ra[1]);
            df.nclasses = (int)Math.Round(ra[2]);
            df.ntrees = (int)Math.Round(ra[3]);
            df.bufsize = (int)Math.Round(ra[4]);
            df.trees = new double[df.bufsize-1+1];
            i1_ = (5) - (0);
            for(i_=0; i_<=df.bufsize-1;i_++)
            {
                df.trees[i_] = ra[i_+i1_];
            }
        }


        /*************************************************************************
        Classification error
        *************************************************************************/
        private static int dfclserror(ref decisionforest df,
            ref double[,] xy,
            int npoints)
        {
            int result = 0;
            double[] x = new double[0];
            double[] y = new double[0];
            int i = 0;
            int j = 0;
            int k = 0;
            int tmpi = 0;
            int i_ = 0;

            if( df.nclasses<=1 )
            {
                result = 0;
                return result;
            }
            x = new double[df.nvars-1+1];
            y = new double[df.nclasses-1+1];
            result = 0;
            for(i=0; i<=npoints-1; i++)
            {
                for(i_=0; i_<=df.nvars-1;i_++)
                {
                    x[i_] = xy[i,i_];
                }
                dfprocess(ref df, ref x, ref y);
                k = (int)Math.Round(xy[i,df.nvars]);
                tmpi = 0;
                for(j=1; j<=df.nclasses-1; j++)
                {
                    if( (double)(y[j])>(double)(y[tmpi]) )
                    {
                        tmpi = j;
                    }
                }
                if( tmpi!=k )
                {
                    result = result+1;
                }
            }
            return result;
        }


        /*************************************************************************
        Internal subroutine for processing one decision tree starting at Offs
        *************************************************************************/
        private static void dfprocessinternal(ref decisionforest df,
            int offs,
            ref double[] x,
            ref double[] y)
        {
            int i = 0;
            int k = 0;
            int idx = 0;

            
            //
            // Set pointer to the root
            //
            k = offs+1;
            
            //
            // Navigate through the tree
            //
            while( true )
            {
                if( (double)(df.trees[k])==(double)(-1) )
                {
                    if( df.nclasses==1 )
                    {
                        y[0] = y[0]+df.trees[k+1];
                    }
                    else
                    {
                        idx = (int)Math.Round(df.trees[k+1]);
                        y[idx] = y[idx]+1;
                    }
                    break;
                }
                if( (double)(x[(int)Math.Round(df.trees[k])])<(double)(df.trees[k+1]) )
                {
                    k = k+innernodewidth;
                }
                else
                {
                    k = offs+(int)Math.Round(df.trees[k+2]);
                }
            }
        }


        /*************************************************************************
        Builds one decision tree. Just a wrapper for the DFBuildTreeRec.
        *************************************************************************/
        private static void dfbuildtree(ref double[,] xy,
            int npoints,
            int nvars,
            int nclasses,
            int nfeatures,
            int nvarsinpool,
            int flags,
            ref dfinternalbuffers bufs)
        {
            int numprocessed = 0;
            int i = 0;

            System.Diagnostics.Debug.Assert(npoints>0);
            
            //
            // Prepare IdxBuf. It stores indices of the training set elements.
            // When training set is being split, contents of IdxBuf is
            // correspondingly reordered so we can know which elements belong
            // to which branch of decision tree.
            //
            for(i=0; i<=npoints-1; i++)
            {
                bufs.idxbuf[i] = i;
            }
            
            //
            // Recursive procedure
            //
            numprocessed = 1;
            dfbuildtreerec(ref xy, npoints, nvars, nclasses, nfeatures, nvarsinpool, flags, ref numprocessed, 0, npoints-1, ref bufs);
            bufs.treebuf[0] = numprocessed;
        }


        /*************************************************************************
        Builds one decision tree (internal recursive subroutine)

        Parameters:
            TreeBuf     -   large enough array, at least TreeSize
            IdxBuf      -   at least NPoints elements
            TmpBufR     -   at least NPoints
            TmpBufR2    -   at least NPoints
            TmpBufI     -   at least NPoints
            TmpBufI2    -   at least NPoints+1
        *************************************************************************/
        private static void dfbuildtreerec(ref double[,] xy,
            int npoints,
            int nvars,
            int nclasses,
            int nfeatures,
            int nvarsinpool,
            int flags,
            ref int numprocessed,
            int idx1,
            int idx2,
            ref dfinternalbuffers bufs)
        {
            int i = 0;
            int j = 0;
            int k = 0;
            bool bflag = new bool();
            int offs = 0;
            int i1 = 0;
            int i2 = 0;
            int lsize = 0;
            int info = 0;
            double sl = 0;
            double sr = 0;
            double w = 0;
            int idxbest = 0;
            double ebest = 0;
            double tbest = 0;
            int varcur = 0;
            double s = 0;
            double v = 0;
            double v1 = 0;
            double v2 = 0;
            int nbuf = 0;
            double threshold = 0;
            int oldnp = 0;
            double e = 0;
            double currms = 0;
            double curcvrms = 0;
            bool useevs = new bool();

            System.Diagnostics.Debug.Assert(npoints>0);
            System.Diagnostics.Debug.Assert(idx2>=idx1);
            useevs = flags/dfuseevs%2!=0;
            
            //
            // Leaf node
            //
            if( idx2==idx1 )
            {
                bufs.treebuf[numprocessed] = -1;
                bufs.treebuf[numprocessed+1] = xy[bufs.idxbuf[idx1],nvars];
                numprocessed = numprocessed+leafnodewidth;
                return;
            }
            
            //
            // Non-leaf node.
            // Select random variable, prepare split:
            // 1. prepare default solution - no splitting, class at random
            // 2. investigate possible splits, compare with default/best
            //
            idxbest = -1;
            if( nclasses>1 )
            {
                
                //
                // default solution for classification
                //
                for(i=0; i<=nclasses-1; i++)
                {
                    bufs.classibuf[i] = 0;
                }
                s = idx2-idx1+1;
                for(i=idx1; i<=idx2; i++)
                {
                    j = (int)Math.Round(xy[bufs.idxbuf[i],nvars]);
                    bufs.classibuf[j] = bufs.classibuf[j]+1;
                }
                ebest = 0;
                for(i=0; i<=nclasses-1; i++)
                {
                    ebest = ebest+bufs.classibuf[i]*AP.Math.Sqr(1-bufs.classibuf[i]/s)+(s-bufs.classibuf[i])*AP.Math.Sqr(bufs.classibuf[i]/s);
                }
                ebest = Math.Sqrt(ebest/(nclasses*(idx2-idx1+1)));
            }
            else
            {
                
                //
                // default solution for regression
                //
                v = 0;
                for(i=idx1; i<=idx2; i++)
                {
                    v = v+xy[bufs.idxbuf[i],nvars];
                }
                v = v/(idx2-idx1+1);
                ebest = 0;
                for(i=idx1; i<=idx2; i++)
                {
                    ebest = ebest+AP.Math.Sqr(xy[bufs.idxbuf[i],nvars]-v);
                }
                ebest = Math.Sqrt(ebest/(idx2-idx1+1));
            }
            i = 0;
            while( i<=Math.Min(nfeatures, nvarsinpool)-1 )
            {
                
                //
                // select variables from pool
                //
                j = i+AP.Math.RandomInteger(nvarsinpool-i);
                k = bufs.varpool[i];
                bufs.varpool[i] = bufs.varpool[j];
                bufs.varpool[j] = k;
                varcur = bufs.varpool[i];
                
                //
                // load variable values to working array
                //
                // apply EVS preprocessing: if all variable values are same,
                // variable is excluded from pool.
                //
                // This is necessary for binary pre-splits (see later) to work.
                //
                for(j=idx1; j<=idx2; j++)
                {
                    bufs.tmpbufr[j-idx1] = xy[bufs.idxbuf[j],varcur];
                }
                if( useevs )
                {
                    bflag = false;
                    v = bufs.tmpbufr[0];
                    for(j=0; j<=idx2-idx1; j++)
                    {
                        if( (double)(bufs.tmpbufr[j])!=(double)(v) )
                        {
                            bflag = true;
                            break;
                        }
                    }
                    if( !bflag )
                    {
                        
                        //
                        // exclude variable from pool,
                        // go to the next iteration.
                        // I is not increased.
                        //
                        k = bufs.varpool[i];
                        bufs.varpool[i] = bufs.varpool[nvarsinpool-1];
                        bufs.varpool[nvarsinpool-1] = k;
                        nvarsinpool = nvarsinpool-1;
                        continue;
                    }
                }
                
                //
                // load labels to working array
                //
                if( nclasses>1 )
                {
                    for(j=idx1; j<=idx2; j++)
                    {
                        bufs.tmpbufi[j-idx1] = (int)Math.Round(xy[bufs.idxbuf[j],nvars]);
                    }
                }
                else
                {
                    for(j=idx1; j<=idx2; j++)
                    {
                        bufs.tmpbufr2[j-idx1] = xy[bufs.idxbuf[j],nvars];
                    }
                }
                
                //
                // calculate split
                //
                if( useevs & bufs.evsbin[varcur] )
                {
                    
                    //
                    // Pre-calculated splits for binary variables.
                    // Threshold is already known, just calculate RMS error
                    //
                    threshold = bufs.evssplits[varcur];
                    if( nclasses>1 )
                    {
                        
                        //
                        // classification-specific code
                        //
                        for(j=0; j<=2*nclasses-1; j++)
                        {
                            bufs.classibuf[j] = 0;
                        }
                        sl = 0;
                        sr = 0;
                        for(j=0; j<=idx2-idx1; j++)
                        {
                            k = bufs.tmpbufi[j];
                            if( (double)(bufs.tmpbufr[j])<(double)(threshold) )
                            {
                                bufs.classibuf[k] = bufs.classibuf[k]+1;
                                sl = sl+1;
                            }
                            else
                            {
                                bufs.classibuf[k+nclasses] = bufs.classibuf[k+nclasses]+1;
                                sr = sr+1;
                            }
                        }
                        System.Diagnostics.Debug.Assert((double)(sl)!=(double)(0) & (double)(sr)!=(double)(0), "DFBuildTreeRec: something strange!");
                        currms = 0;
                        for(j=0; j<=nclasses-1; j++)
                        {
                            w = bufs.classibuf[j];
                            currms = currms+w*AP.Math.Sqr(w/sl-1);
                            currms = currms+(sl-w)*AP.Math.Sqr(w/sl);
                            w = bufs.classibuf[nclasses+j];
                            currms = currms+w*AP.Math.Sqr(w/sr-1);
                            currms = currms+(sr-w)*AP.Math.Sqr(w/sr);
                        }
                        currms = Math.Sqrt(currms/(nclasses*(idx2-idx1+1)));
                    }
                    else
                    {
                        
                        //
                        // regression-specific code
                        //
                        sl = 0;
                        sr = 0;
                        v1 = 0;
                        v2 = 0;
                        for(j=0; j<=idx2-idx1; j++)
                        {
                            if( (double)(bufs.tmpbufr[j])<(double)(threshold) )
                            {
                                v1 = v1+bufs.tmpbufr2[j];
                                sl = sl+1;
                            }
                            else
                            {
                                v2 = v2+bufs.tmpbufr2[j];
                                sr = sr+1;
                            }
                        }
                        System.Diagnostics.Debug.Assert((double)(sl)!=(double)(0) & (double)(sr)!=(double)(0), "DFBuildTreeRec: something strange!");
                        v1 = v1/sl;
                        v2 = v2/sr;
                        currms = 0;
                        for(j=0; j<=idx2-idx1; j++)
                        {
                            if( (double)(bufs.tmpbufr[j])<(double)(threshold) )
                            {
                                currms = currms+AP.Math.Sqr(v1-bufs.tmpbufr2[j]);
                            }
                            else
                            {
                                currms = currms+AP.Math.Sqr(v2-bufs.tmpbufr2[j]);
                            }
                        }
                        currms = Math.Sqrt(currms/(idx2-idx1+1));
                    }
                    info = 1;
                }
                else
                {
                    
                    //
                    // Generic splits
                    //
                    if( nclasses>1 )
                    {
                        dfsplitc(ref bufs.tmpbufr, ref bufs.tmpbufi, ref bufs.classibuf, idx2-idx1+1, nclasses, dfusestrongsplits, ref info, ref threshold, ref currms);
                    }
                    else
                    {
                        dfsplitr(ref bufs.tmpbufr, ref bufs.tmpbufr2, idx2-idx1+1, dfusestrongsplits, ref info, ref threshold, ref currms);
                    }
                }
                if( info>0 )
                {
                    if( (double)(currms)<=(double)(ebest) )
                    {
                        ebest = currms;
                        idxbest = varcur;
                        tbest = threshold;
                    }
                }
                
                //
                // Next iteration
                //
                i = i+1;
            }
            
            //
            // to split or not to split
            //
            if( idxbest<0 )
            {
                
                //
                // All values are same, cannot split.
                //
                bufs.treebuf[numprocessed] = -1;
                if( nclasses>1 )
                {
                    
                    //
                    // Select random class label (randomness allows us to
                    // approximate distribution of the classes)
                    //
                    bufs.treebuf[numprocessed+1] = (int)Math.Round(xy[bufs.idxbuf[idx1+AP.Math.RandomInteger(idx2-idx1+1)],nvars]);
                }
                else
                {
                    
                    //
                    // Select average (for regression task).
                    //
                    v = 0;
                    for(i=idx1; i<=idx2; i++)
                    {
                        v = v+xy[bufs.idxbuf[i],nvars]/(idx2-idx1+1);
                    }
                    bufs.treebuf[numprocessed+1] = v;
                }
                numprocessed = numprocessed+leafnodewidth;
            }
            else
            {
                
                //
                // we can split
                //
                bufs.treebuf[numprocessed] = idxbest;
                bufs.treebuf[numprocessed+1] = tbest;
                i1 = idx1;
                i2 = idx2;
                while( i1<=i2 )
                {
                    
                    //
                    // Reorder indices so that left partition is in [Idx1..I1-1],
                    // and right partition is in [I2+1..Idx2]
                    //
                    if( (double)(xy[bufs.idxbuf[i1],idxbest])<(double)(tbest) )
                    {
                        i1 = i1+1;
                        continue;
                    }
                    if( (double)(xy[bufs.idxbuf[i2],idxbest])>=(double)(tbest) )
                    {
                        i2 = i2-1;
                        continue;
                    }
                    j = bufs.idxbuf[i1];
                    bufs.idxbuf[i1] = bufs.idxbuf[i2];
                    bufs.idxbuf[i2] = j;
                    i1 = i1+1;
                    i2 = i2-1;
                }
                oldnp = numprocessed;
                numprocessed = numprocessed+innernodewidth;
                dfbuildtreerec(ref xy, npoints, nvars, nclasses, nfeatures, nvarsinpool, flags, ref numprocessed, idx1, i1-1, ref bufs);
                bufs.treebuf[oldnp+2] = numprocessed;
                dfbuildtreerec(ref xy, npoints, nvars, nclasses, nfeatures, nvarsinpool, flags, ref numprocessed, i2+1, idx2, ref bufs);
            }
        }


        /*************************************************************************
        Makes weak split on attribute
        *************************************************************************/
        private static void dfweakspliti(ref double[] x,
            ref int[] y,
            int n,
            int nclasses,
            ref int info,
            ref double threshold,
            ref double e)
        {
            int i = 0;
            int neq = 0;
            int nless = 0;
            int ngreater = 0;

            tsort.tagsortfasti(ref x, ref y, n);
            if( n%2==1 )
            {
                
                //
                // odd number of elements
                //
                threshold = x[n/2];
            }
            else
            {
                
                //
                // even number of elements.
                //
                // if two closest to the middle of the array are equal,
                // we will select one of them (to avoid possible problems with
                // floating point errors).
                // we will select halfsum otherwise.
                //
                if( (double)(x[n/2-1])==(double)(x[n/2]) )
                {
                    threshold = x[n/2-1];
                }
                else
                {
                    threshold = 0.5*(x[n/2-1]+x[n/2]);
                }
            }
            neq = 0;
            nless = 0;
            ngreater = 0;
            for(i=0; i<=n-1; i++)
            {
                if( (double)(x[i])<(double)(threshold) )
                {
                    nless = nless+1;
                }
                if( (double)(x[i])==(double)(threshold) )
                {
                    neq = neq+1;
                }
                if( (double)(x[i])>(double)(threshold) )
                {
                    ngreater = ngreater+1;
                }
            }
            if( nless==0 & ngreater==0 )
            {
                info = -3;
            }
            else
            {
                if( neq!=0 )
                {
                    if( nless<ngreater )
                    {
                        threshold = 0.5*(x[nless+neq-1]+x[nless+neq]);
                    }
                    else
                    {
                        threshold = 0.5*(x[nless-1]+x[nless]);
                    }
                }
                info = 1;
                e = 0;
            }
        }


        /*************************************************************************
        Makes split on attribute
        *************************************************************************/
        private static void dfsplitc(ref double[] x,
            ref int[] c,
            ref int[] cntbuf,
            int n,
            int nc,
            int flags,
            ref int info,
            ref double threshold,
            ref double e)
        {
            int i = 0;
            int neq = 0;
            int nless = 0;
            int ngreater = 0;
            int q = 0;
            int qmin = 0;
            int qmax = 0;
            int qcnt = 0;
            double cursplit = 0;
            int nleft = 0;
            double v = 0;
            double cure = 0;
            double w = 0;
            double sl = 0;
            double sr = 0;

            tsort.tagsortfasti(ref x, ref c, n);
            e = AP.Math.MaxRealNumber;
            threshold = 0.5*(x[0]+x[n-1]);
            info = -3;
            if( flags/dfusestrongsplits%2==0 )
            {
                
                //
                // weak splits, split at half
                //
                qcnt = 2;
                qmin = 1;
                qmax = 1;
            }
            else
            {
                
                //
                // strong splits: choose best quartile
                //
                qcnt = 4;
                qmin = 1;
                qmax = 3;
            }
            for(q=qmin; q<=qmax; q++)
            {
                cursplit = x[n*q/qcnt];
                neq = 0;
                nless = 0;
                ngreater = 0;
                for(i=0; i<=n-1; i++)
                {
                    if( (double)(x[i])<(double)(cursplit) )
                    {
                        nless = nless+1;
                    }
                    if( (double)(x[i])==(double)(cursplit) )
                    {
                        neq = neq+1;
                    }
                    if( (double)(x[i])>(double)(cursplit) )
                    {
                        ngreater = ngreater+1;
                    }
                }
                System.Diagnostics.Debug.Assert(neq!=0, "DFSplitR: NEq=0, something strange!!!");
                if( nless!=0 | ngreater!=0 )
                {
                    
                    //
                    // set threshold between two partitions, with
                    // some tweaking to avoid problems with floating point
                    // arithmetics.
                    //
                    // The problem is that when you calculates C = 0.5*(A+B) there
                    // can be no C which lies strictly between A and B (for example,
                    // there is no floating point number which is
                    // greater than 1 and less than 1+eps). In such situations
                    // we choose right side as theshold (remember that
                    // points which lie on threshold falls to the right side).
                    //
                    if( nless<ngreater )
                    {
                        cursplit = 0.5*(x[nless+neq-1]+x[nless+neq]);
                        nleft = nless+neq;
                        if( (double)(cursplit)<=(double)(x[nless+neq-1]) )
                        {
                            cursplit = x[nless+neq];
                        }
                    }
                    else
                    {
                        cursplit = 0.5*(x[nless-1]+x[nless]);
                        nleft = nless;
                        if( (double)(cursplit)<=(double)(x[nless-1]) )
                        {
                            cursplit = x[nless];
                        }
                    }
                    info = 1;
                    cure = 0;
                    for(i=0; i<=2*nc-1; i++)
                    {
                        cntbuf[i] = 0;
                    }
                    for(i=0; i<=nleft-1; i++)
                    {
                        cntbuf[c[i]] = cntbuf[c[i]]+1;
                    }
                    for(i=nleft; i<=n-1; i++)
                    {
                        cntbuf[nc+c[i]] = cntbuf[nc+c[i]]+1;
                    }
                    sl = nleft;
                    sr = n-nleft;
                    v = 0;
                    for(i=0; i<=nc-1; i++)
                    {
                        w = cntbuf[i];
                        v = v+w*AP.Math.Sqr(w/sl-1);
                        v = v+(sl-w)*AP.Math.Sqr(w/sl);
                        w = cntbuf[nc+i];
                        v = v+w*AP.Math.Sqr(w/sr-1);
                        v = v+(sr-w)*AP.Math.Sqr(w/sr);
                    }
                    cure = Math.Sqrt(v/(nc*n));
                    if( (double)(cure)<(double)(e) )
                    {
                        threshold = cursplit;
                        e = cure;
                    }
                }
            }
        }


        /*************************************************************************
        Makes split on attribute
        *************************************************************************/
        private static void dfsplitr(ref double[] x,
            ref double[] y,
            int n,
            int flags,
            ref int info,
            ref double threshold,
            ref double e)
        {
            int i = 0;
            int neq = 0;
            int nless = 0;
            int ngreater = 0;
            int q = 0;
            int qmin = 0;
            int qmax = 0;
            int qcnt = 0;
            double cursplit = 0;
            int nleft = 0;
            double v = 0;
            double cure = 0;

            tsort.tagsortfastr(ref x, ref y, n);
            e = AP.Math.MaxRealNumber;
            threshold = 0.5*(x[0]+x[n-1]);
            info = -3;
            if( flags/dfusestrongsplits%2==0 )
            {
                
                //
                // weak splits, split at half
                //
                qcnt = 2;
                qmin = 1;
                qmax = 1;
            }
            else
            {
                
                //
                // strong splits: choose best quartile
                //
                qcnt = 4;
                qmin = 1;
                qmax = 3;
            }
            for(q=qmin; q<=qmax; q++)
            {
                cursplit = x[n*q/qcnt];
                neq = 0;
                nless = 0;
                ngreater = 0;
                for(i=0; i<=n-1; i++)
                {
                    if( (double)(x[i])<(double)(cursplit) )
                    {
                        nless = nless+1;
                    }
                    if( (double)(x[i])==(double)(cursplit) )
                    {
                        neq = neq+1;
                    }
                    if( (double)(x[i])>(double)(cursplit) )
                    {
                        ngreater = ngreater+1;
                    }
                }
                System.Diagnostics.Debug.Assert(neq!=0, "DFSplitR: NEq=0, something strange!!!");
                if( nless!=0 | ngreater!=0 )
                {
                    
                    //
                    // set threshold between two partitions, with
                    // some tweaking to avoid problems with floating point
                    // arithmetics.
                    //
                    // The problem is that when you calculates C = 0.5*(A+B) there
                    // can be no C which lies strictly between A and B (for example,
                    // there is no floating point number which is
                    // greater than 1 and less than 1+eps). In such situations
                    // we choose right side as theshold (remember that
                    // points which lie on threshold falls to the right side).
                    //
                    if( nless<ngreater )
                    {
                        cursplit = 0.5*(x[nless+neq-1]+x[nless+neq]);
                        nleft = nless+neq;
                        if( (double)(cursplit)<=(double)(x[nless+neq-1]) )
                        {
                            cursplit = x[nless+neq];
                        }
                    }
                    else
                    {
                        cursplit = 0.5*(x[nless-1]+x[nless]);
                        nleft = nless;
                        if( (double)(cursplit)<=(double)(x[nless-1]) )
                        {
                            cursplit = x[nless];
                        }
                    }
                    info = 1;
                    cure = 0;
                    v = 0;
                    for(i=0; i<=nleft-1; i++)
                    {
                        v = v+y[i];
                    }
                    v = v/nleft;
                    for(i=0; i<=nleft-1; i++)
                    {
                        cure = cure+AP.Math.Sqr(y[i]-v);
                    }
                    v = 0;
                    for(i=nleft; i<=n-1; i++)
                    {
                        v = v+y[i];
                    }
                    v = v/(n-nleft);
                    for(i=nleft; i<=n-1; i++)
                    {
                        cure = cure+AP.Math.Sqr(y[i]-v);
                    }
                    cure = Math.Sqrt(cure/n);
                    if( (double)(cure)<(double)(e) )
                    {
                        threshold = cursplit;
                        e = cure;
                    }
                }
            }
        }
    }
}