/*
 * Copyright(C) 1999-2020, 2023 National Technology & Engineering Solutions
 * of Sandia, LLC (NTESS).  Under the terms of Contract DE-NA0003525 with
 * NTESS, the U.S. Government retains certain rights in this software.
 *
 * See packages/seacas/LICENSE for details
 */

#include "params.h"  // for MAXSETS
#include "structs.h" // for vtx_data

void inits3d(struct vtx_data **graph,                /* graph data structure for vertex weights */
             double          **xvecs,                /* values to partition with */
             double           *vals[8][MAXSETS],     /* values in sorted lists */
             int              *indices[8][MAXSETS],  /* indices sorting lists */
             int               nvtxs,                /* number of vertices */
             double           *dist,                 /* trial separation point */
             int               startvtx[8][MAXSETS], /* indices defining separation */
             double           *size,                 /* size of each set being modified */
             int              *sets                  /* set each vertex gets assigned to */
)
{
  double xmid, ymid, zmid;    /* median x, y and z values */
  double val, bestval;        /* values for determining set preferences */
  int    bestset = 0;         /* set vertex wants to be in */
  int    signx, signy, signz; /* sign values for different target points */
  int    nsets = 8;           /* number of different sets */
  int    i, j;                /* loop counters */

  /*
      xmid = .25 * (vals[0][1][indices[0][1][nvtxs / 2]] +
                    vals[0][1][indices[0][1][nvtxs / 2 - 1]]);
      ymid = .25 * (vals[0][2][indices[0][2][nvtxs / 2]] +
                    vals[0][2][indices[0][2][nvtxs / 2 - 1]]);
      zmid = .25 * (vals[0][4][indices[0][4][nvtxs / 2]] +
                    vals[0][4][indices[0][4][nvtxs / 2 - 1]]);
  */
  xmid = .5 * vals[0][1][indices[0][1][nvtxs / 2]];
  ymid = .5 * vals[0][2][indices[0][2][nvtxs / 2]];
  zmid = .5 * vals[0][4][indices[0][4][nvtxs / 2]];

  dist[0] = -xmid - ymid - zmid;
  dist[1] = xmid - ymid - zmid;
  dist[2] = -xmid + ymid - zmid;
  dist[3] = xmid + ymid - zmid;
  dist[4] = -xmid - ymid + zmid;
  dist[5] = xmid - ymid + zmid;
  dist[6] = -xmid + ymid + zmid;
  dist[7] = xmid + ymid + zmid;

  /* Now initialize startvtxs. */
  startvtx[0][1] = startvtx[2][3] = startvtx[4][5] = startvtx[6][7] = nvtxs / 2;
  startvtx[0][2] = startvtx[1][3] = startvtx[4][6] = startvtx[5][7] = nvtxs / 2;
  startvtx[0][4] = startvtx[1][5] = startvtx[2][6] = startvtx[3][7] = nvtxs / 2;
  startvtx[0][3] = startvtx[4][7] = findindex(indices[0][3], vals[0][3], dist[3] - dist[0], nvtxs);
  startvtx[1][2] = startvtx[5][6] = findindex(indices[1][2], vals[1][2], dist[2] - dist[1], nvtxs);
  startvtx[0][5] = startvtx[2][7] = findindex(indices[0][5], vals[0][5], dist[5] - dist[0], nvtxs);
  startvtx[1][4] = startvtx[3][6] = findindex(indices[1][4], vals[1][4], dist[4] - dist[1], nvtxs);
  startvtx[0][6] = startvtx[1][7] = findindex(indices[0][6], vals[0][6], dist[6] - dist[0], nvtxs);
  startvtx[2][4] = startvtx[3][5] = findindex(indices[2][4], vals[2][4], dist[4] - dist[2], nvtxs);
  startvtx[0][7]                  = findindex(indices[0][7], vals[0][7], dist[7] - dist[0], nvtxs);
  startvtx[1][6]                  = findindex(indices[1][6], vals[1][6], dist[6] - dist[1], nvtxs);
  startvtx[2][5]                  = findindex(indices[2][5], vals[2][5], dist[5] - dist[2], nvtxs);
  startvtx[3][4]                  = findindex(indices[3][4], vals[3][4], dist[4] - dist[3], nvtxs);

  /* Finally, determine the set sizes based on this splitter. */

  for (i = 0; i < nsets; i++) {
    size[i] = 0;
  }

  for (i = 1; i <= nvtxs; i++) {
    /* Which set is this vertex in? */
    signx = signy = signz = -1;
    bestval               = 0;
    for (j = 0; j < nsets; j++) {
      val = -dist[j] + 2 * (signx * xvecs[1][i] + signy * xvecs[2][i] + signz * xvecs[3][i]);
      if (j == 0 || val < bestval) {
        bestval = val;
        bestset = j;
      }
      if (signx == 1 && signy == 1) {
        signz *= -1;
      }
      if (signx == 1) {
        signy *= -1;
      }
      signx *= -1;
    }
    sets[i] = bestset;
    size[bestset] += graph[i]->vwgt;
  }
}