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/*
 * The routine which will find the best split for a node
 *
 * Input :      node
 *              node number
 *
 * Output:      Fills in the node's
 *                      primary splits
 *                      competitor splits
 */
#include "rpart.h"
#include "node.h"
#include "rpartproto.h"

void
bsplit(pNode me, int n1, int n2)
{
    int i, j, k;
    int kk;
    int nc;
    double improve;
    double split = 0.0;
    pSplit tsplit;
    int *index;
    double *xtemp;              /* these 3 because I got tired of typeing
                 * "rp.xtemp", etc */
    double **ytemp;
    double *wtemp;

    xtemp = rp.xtemp;
    ytemp = rp.ytemp;
    wtemp = rp.wtemp;

    /*
     * test out the variables 1 at at time
     */
    me->primary = (pSplit) NULL;
    for (i = 0; i < rp.nvar; i++) {
    index = rp.sorts[i];
    nc = rp.numcat[i];
       /* extract x and y data */
    k = 0;
    for (j = n1; j < n2; j++) {
        kk = index[j];
        if (kk >= 0 && rp.wt[kk] > 0) {  /* x data not missing and wt > 0 */
        xtemp[k] = rp.xdata[i][kk];
        ytemp[k] = rp.ydata[kk];
        wtemp[k] = rp.wt[kk];
        k++;
        }
    }

    if (k == 0 || (nc == 0 && xtemp[0] == xtemp[k - 1]))
        continue;           /* no place to split */

    (*rp_choose) (k, ytemp, xtemp, nc, rp.min_node, &improve,
              &split, rp.csplit, me->risk, wtemp);

       /*
    * Originally, this just said "if (improve > 0)", but rounding
    * error will sometimes create a non zero that should be 0.  Yet we
    * want to retain invariance to the scale of "improve".
    */
    if (improve > rp.iscale)
        rp.iscale = improve;        /* largest seen so far */
    if (improve > (rp.iscale * 1e-10)) {
        improve /= rp.vcost[i];     /* scale the improvement */
        tsplit = insert_split(&(me->primary), nc, improve, rp.maxpri);
        if (tsplit) {
        tsplit->improve = improve;
        tsplit->var_num = i;
        tsplit->spoint = split;
        tsplit->count = k;
        if (nc == 0) {
            tsplit->spoint = split;
            tsplit->csplit[0] = rp.csplit[0];
        } else
            for (k = 0; k < nc; k++)
            tsplit->csplit[k] = rp.csplit[k];
        }
    }
    }
}