static char help[] = "Tests DMSwarm with DMShell\n\n";

#include <petscsf.h>
#include <petscdm.h>
#include <petscdmshell.h>
#include <petscdmda.h>
#include <petscdmswarm.h>
#include <petsc/private/dmimpl.h>

PetscErrorCode _DMLocatePoints_DMDARegular_IS(DM dm,Vec pos,IS *iscell)
{
  PetscInt       p,n,bs,npoints,si,sj,milocal,mjlocal,mx,my;
  DM             dmregular;
  PetscInt       *cellidx;
  const PetscScalar *coor;
  PetscReal      dx,dy;
  PetscMPIInt    rank;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank));
  PetscCall(VecGetLocalSize(pos,&n));
  PetscCall(VecGetBlockSize(pos,&bs));
  npoints = n/bs;

  PetscCall(PetscMalloc1(npoints,&cellidx));
  PetscCall(DMGetApplicationContext(dm,&dmregular));
  PetscCall(DMDAGetCorners(dmregular,&si,&sj,NULL,&milocal,&mjlocal,NULL));
  PetscCall(DMDAGetInfo(dmregular,NULL,&mx,&my,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL));

  dx = 2.0/((PetscReal)mx);
  dy = 2.0/((PetscReal)my);

  PetscCall(VecGetArrayRead(pos,&coor));
  for (p=0; p<npoints; p++) {
    PetscReal coorx,coory;
    PetscInt  mi,mj;

    coorx = PetscRealPart(coor[2*p]);
    coory = PetscRealPart(coor[2*p+1]);

    mi = (PetscInt)( (coorx - (-1.0))/dx);
    mj = (PetscInt)( (coory - (-1.0))/dy);

    cellidx[p] = DMLOCATEPOINT_POINT_NOT_FOUND;

    if ((mj >= sj) && (mj < sj + mjlocal)) {
      if ((mi >= si) && (mi < si + milocal)) {
        cellidx[p] = (mi-si) + (mj-sj) * milocal;
      }
    }
    if (coorx < -1.0) cellidx[p] = DMLOCATEPOINT_POINT_NOT_FOUND;
    if (coorx >  1.0) cellidx[p] = DMLOCATEPOINT_POINT_NOT_FOUND;
    if (coory < -1.0) cellidx[p] = DMLOCATEPOINT_POINT_NOT_FOUND;
    if (coory >  1.0) cellidx[p] = DMLOCATEPOINT_POINT_NOT_FOUND;
  }
  PetscCall(VecRestoreArrayRead(pos,&coor));
  PetscCall(ISCreateGeneral(PETSC_COMM_SELF,npoints,cellidx,PETSC_OWN_POINTER,iscell));
  PetscFunctionReturn(0);
}

PetscErrorCode DMLocatePoints_DMDARegular(DM dm,Vec pos,DMPointLocationType ltype, PetscSF cellSF)
{
  IS             iscell;
  PetscSFNode    *cells;
  PetscInt       p,bs,npoints,nfound;
  const PetscInt *boxCells;

  PetscFunctionBegin;
  PetscCall(_DMLocatePoints_DMDARegular_IS(dm,pos,&iscell));
  PetscCall(VecGetLocalSize(pos,&npoints));
  PetscCall(VecGetBlockSize(pos,&bs));
  npoints = npoints / bs;

  PetscCall(PetscMalloc1(npoints, &cells));
  PetscCall(ISGetIndices(iscell, &boxCells));

  for (p=0; p<npoints; p++) {
    cells[p].rank  = 0;
    cells[p].index = DMLOCATEPOINT_POINT_NOT_FOUND;
    cells[p].index = boxCells[p];
  }
  PetscCall(ISRestoreIndices(iscell, &boxCells));
  PetscCall(ISDestroy(&iscell));
  nfound = npoints;
  PetscCall(PetscSFSetGraph(cellSF, npoints, nfound, NULL, PETSC_OWN_POINTER, cells, PETSC_OWN_POINTER));
  PetscCall(ISDestroy(&iscell));
  PetscFunctionReturn(0);
}

PetscErrorCode DMGetNeighbors_DMDARegular(DM dm,PetscInt *nneighbors,const PetscMPIInt **neighbors)
{
  DM             dmregular;

  PetscFunctionBegin;
  PetscCall(DMGetApplicationContext(dm,&dmregular));
  PetscCall(DMGetNeighbors(dmregular,nneighbors,neighbors));
  PetscFunctionReturn(0);
}

PetscErrorCode SwarmViewGP(DM dms,const char prefix[])
{
  PetscReal      *array;
  PetscInt       *iarray;
  PetscInt       npoints,p,bs;
  FILE           *fp;
  char           name[PETSC_MAX_PATH_LEN];
  PetscMPIInt    rank;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank));
  PetscCall(PetscSNPrintf(name,PETSC_MAX_PATH_LEN-1,"%s-rank%d.gp",prefix,rank));
  fp = fopen(name,"w");
  PetscCheck(fp,PETSC_COMM_SELF,PETSC_ERR_FILE_OPEN,"Cannot open file %s",name);
  PetscCall(DMSwarmGetLocalSize(dms,&npoints));
  PetscCall(DMSwarmGetField(dms,DMSwarmPICField_coor,&bs,NULL,(void**)&array));
  PetscCall(DMSwarmGetField(dms,"itag",NULL,NULL,(void**)&iarray));
  for (p=0; p<npoints; p++) {
    fprintf(fp,"%+1.4e %+1.4e %1.4e\n",array[2*p],array[2*p+1],(double)iarray[p]);
  }
  PetscCall(DMSwarmRestoreField(dms,"itag",NULL,NULL,(void**)&iarray));
  PetscCall(DMSwarmRestoreField(dms,DMSwarmPICField_coor,&bs,NULL,(void**)&array));
  fclose(fp);
  PetscFunctionReturn(0);
}

/*
 Create a DMShell and attach a regularly spaced DMDA for point location
 Override methods for point location
*/
PetscErrorCode ex3_1(void)
{
  DM             dms,dmcell,dmregular;
  PetscMPIInt    rank;
  PetscInt       p,bs,nlocal,overlap,mx,tk;
  PetscReal      dx;
  PetscReal      *array,dt;
  PetscInt       *iarray;
  PetscRandom    rand;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank));

  /* Create a regularly spaced DMDA */
  mx = 40;
  overlap = 0;
  PetscCall(DMDACreate2d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,DM_BOUNDARY_NONE,DMDA_STENCIL_BOX,mx,mx,PETSC_DECIDE,PETSC_DECIDE,1,overlap,NULL,NULL,&dmregular));
  PetscCall(DMSetFromOptions(dmregular));
  PetscCall(DMSetUp(dmregular));

  dx = 2.0/((PetscReal)mx);
  PetscCall(DMDASetUniformCoordinates(dmregular,-1.0+0.5*dx,1.0-0.5*dx,-1.0+0.5*dx,1.0-0.5*dx,-1.0,1.0));

  /* Create a DMShell for point location purposes */
  PetscCall(DMShellCreate(PETSC_COMM_WORLD,&dmcell));
  PetscCall(DMSetApplicationContext(dmcell,dmregular));
  dmcell->ops->locatepoints = DMLocatePoints_DMDARegular;
  dmcell->ops->getneighbors = DMGetNeighbors_DMDARegular;

  /* Create the swarm */
  PetscCall(DMCreate(PETSC_COMM_WORLD,&dms));
  PetscCall(DMSetType(dms,DMSWARM));
  PetscCall(DMSetDimension(dms,2));
  PetscCall(PetscObjectSetName((PetscObject) dms, "Particles"));

  PetscCall(DMSwarmSetType(dms,DMSWARM_PIC));
  PetscCall(DMSwarmSetCellDM(dms,dmcell));

  PetscCall(DMSwarmRegisterPetscDatatypeField(dms,"itag",1,PETSC_INT));
  PetscCall(DMSwarmFinalizeFieldRegister(dms));
  {
    PetscInt  si,sj,milocal,mjlocal;
    const PetscScalar *LA_coors;
    Vec       coors;
    PetscInt  cnt;

    PetscCall(DMDAGetCorners(dmregular,&si,&sj,NULL,&milocal,&mjlocal,NULL));
    PetscCall(DMGetCoordinates(dmregular,&coors));
    PetscCall(VecGetArrayRead(coors,&LA_coors));
    PetscCall(DMSwarmSetLocalSizes(dms,milocal*mjlocal,4));
    PetscCall(DMSwarmGetLocalSize(dms,&nlocal));
    PetscCall(DMSwarmGetField(dms,DMSwarmPICField_coor,&bs,NULL,(void**)&array));
    cnt = 0;
    PetscCall(PetscRandomCreate(PETSC_COMM_SELF,&rand));
    PetscCall(PetscRandomSetInterval(rand,-1.0,1.0));
    for (p=0; p<nlocal; p++) {
      PetscReal px,py,rx,ry,r2;

      PetscCall(PetscRandomGetValueReal(rand,&rx));
      PetscCall(PetscRandomGetValueReal(rand,&ry));

      px = PetscRealPart(LA_coors[2*p+0]) + 0.1*rx*dx;
      py = PetscRealPart(LA_coors[2*p+1]) + 0.1*ry*dx;

      r2 = px*px + py*py;
      if (r2 < 0.75*0.75) {
        array[bs*cnt+0] = px;
        array[bs*cnt+1] = py;
        cnt++;
      }
    }
    PetscCall(PetscRandomDestroy(&rand));
    PetscCall(DMSwarmRestoreField(dms,DMSwarmPICField_coor,&bs,NULL,(void**)&array));
    PetscCall(VecRestoreArrayRead(coors,&LA_coors));
    PetscCall(DMSwarmSetLocalSizes(dms,cnt,4));

    PetscCall(DMSwarmGetLocalSize(dms,&nlocal));
    PetscCall(DMSwarmGetField(dms,"itag",&bs,NULL,(void**)&iarray));
    for (p=0; p<nlocal; p++) {
      iarray[p] = (PetscInt)rank;
    }
    PetscCall(DMSwarmRestoreField(dms,"itag",&bs,NULL,(void**)&iarray));
  }

  PetscCall(DMView(dms,PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(SwarmViewGP(dms,"step0"));

  dt = 0.1;
  for (tk=1; tk<20; tk++) {
    char prefix[PETSC_MAX_PATH_LEN];
    PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Step %" PetscInt_FMT " \n",tk));
    /* push points */
    PetscCall(DMSwarmGetLocalSize(dms,&nlocal));
    PetscCall(DMSwarmGetField(dms,DMSwarmPICField_coor,&bs,NULL,(void**)&array));
    for (p=0; p<nlocal; p++) {
      PetscReal cx,cy,vx,vy;

      cx = array[2*p];
      cy = array[2*p+1];
      vx =  cy;
      vy = -cx;

      array[2*p  ] += dt * vx;
      array[2*p+1] += dt * vy;
    }
    PetscCall(DMSwarmRestoreField(dms,DMSwarmPICField_coor,&bs,NULL,(void**)&array));

    /* migrate points */
    PetscCall(DMSwarmMigrate(dms,PETSC_TRUE));
    /* view points */
    PetscCall(PetscSNPrintf(prefix,PETSC_MAX_PATH_LEN-1,"step%" PetscInt_FMT,tk));
    /* should use the regular SwarmView() api, not one for a particular type */
    PetscCall(SwarmViewGP(dms,prefix));
  }
  PetscCall(DMDestroy(&dmregular));
  PetscCall(DMDestroy(&dmcell));
  PetscCall(DMDestroy(&dms));
  PetscFunctionReturn(0);
}

int main(int argc,char **argv)
{

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc,&argv,(char*)0,help));
  PetscCall(ex3_1());
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   build:
      requires: double !complex

   test:
      filter: grep -v atomic
      filter_output: grep -v atomic
TEST*/