static char help[] = "Tests DMDAVecGetKokkosOffsetView() and DMDAVecGetKokkosOffsetViewDOF() \n\n";

#include <petscdmda_kokkos.hpp>
#include <petscdm.h>
#include <petscdmda.h>

using Kokkos::Iterate;
using Kokkos::MDRangePolicy;
using Kokkos::Rank;
using PetscScalarKokkosOffsetView2D      = Kokkos::Experimental::OffsetView<PetscScalar **, Kokkos::LayoutRight, Kokkos::DefaultExecutionSpace::memory_space>;
using ConstPetscScalarKokkosOffsetView2D = Kokkos::Experimental::OffsetView<const PetscScalar **, Kokkos::LayoutRight, Kokkos::DefaultExecutionSpace::memory_space>;

using PetscScalarKokkosOffsetView3D      = Kokkos::Experimental::OffsetView<PetscScalar ***, Kokkos::LayoutRight, Kokkos::DefaultExecutionSpace::memory_space>;
using ConstPetscScalarKokkosOffsetView3D = Kokkos::Experimental::OffsetView<const PetscScalar ***, Kokkos::LayoutRight, Kokkos::DefaultExecutionSpace::memory_space>;

/* can not define the type inside main, otherwise have this compilation error:
   error: A type local to a function ("Node") cannot be used in the type of a
   variable captured by an extended __device__ or __host__ __device__ lambda
*/
typedef struct {
  PetscScalar u, v, w;
} Node;

using NodeKokkosOffsetView2D      = Kokkos::Experimental::OffsetView<Node **, Kokkos::LayoutRight, Kokkos::DefaultExecutionSpace::memory_space>;
using ConstNodeKokkosOffsetView2D = Kokkos::Experimental::OffsetView<const Node **, Kokkos::LayoutRight, Kokkos::DefaultExecutionSpace::memory_space>;

int main(int argc, char **argv)
{
  DM              da;
  PetscInt        M = 5, N = 7, xm, ym, xs, ys;
  PetscInt        dof = 1, sw = 1;
  DMBoundaryType  bx = DM_BOUNDARY_PERIODIC, by = DM_BOUNDARY_PERIODIC;
  DMDAStencilType st = DMDA_STENCIL_STAR;
  PetscReal       nrm;
  Vec             g, l, gg, ll; /* global/local vectors of the da */

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, nullptr, help));

  /* ===========================================================================
    Show how to manage a multi-component DMDA with DMDAVecGetKokkosOffsetViewDOF
   ============================================================================*/
  PetscScalar                     ***garray; /* arrays of g, ll */
  const PetscScalar               ***larray;
  PetscScalarKokkosOffsetView3D      gview; /* views of gg, ll */
  ConstPetscScalarKokkosOffsetView3D lview;

  dof = 2;
  PetscCall(DMDACreate2d(PETSC_COMM_WORLD, bx, by, st, M, N, PETSC_DECIDE, PETSC_DECIDE, dof, sw, NULL, NULL, &da));
  PetscCall(DMSetFromOptions(da));
  PetscCall(DMSetUp(da));
  PetscCall(DMDAGetCorners(da, &xs, &ys, 0, &xm, &ym, 0));
  PetscCall(DMCreateGlobalVector(da, &g));
  PetscCall(DMCreateLocalVector(da, &l));
  PetscCall(DMCreateGlobalVector(da, &gg));
  PetscCall(DMCreateLocalVector(da, &ll));

  /* Init g using array */
  PetscCall(DMDAVecGetArrayDOFWrite(da, g, &garray));
  for (PetscInt j = ys; j < ys + ym; j++) { /* run on host */
    for (PetscInt i = xs; i < xs + xm; i++) {
      for (PetscInt c = 0; c < dof; c++) garray[j][i][c] = 100 * j + 10 * (i + 1) + c;
    }
  }
  PetscCall(DMDAVecRestoreArrayDOFWrite(da, g, &garray));

  /* Init gg using view */
  PetscCall(DMDAVecGetKokkosOffsetViewDOFWrite(da, gg, &gview));
  Kokkos::parallel_for(
    "init 1", MDRangePolicy<Rank<3, Iterate::Right, Iterate::Right>>({ys, xs, 0}, {ys + ym, xs + xm, dof}),
    KOKKOS_LAMBDA(PetscInt j, PetscInt i, PetscInt c) /* might run on device */
    { gview(j, i, c) = 100 * j + 10 * (i + 1) + c; });
  PetscCall(DMDAVecRestoreKokkosOffsetViewDOFWrite(da, gg, &gview));

  /* Scatter g, gg to l, ll */
  PetscCall(DMGlobalToLocal(da, g, INSERT_VALUES, l));
  PetscCall(DMGlobalToLocal(da, gg, INSERT_VALUES, ll));

  /* Do stencil on g with values from l that contains ghosts */
  PetscCall(DMDAVecGetArrayDOFWrite(da, g, &garray));
  PetscCall(DMDAVecGetArrayDOFRead(da, l, &larray));
  for (PetscInt j = ys; j < ys + ym; j++) {
    for (PetscInt i = xs; i < xs + xm; i++) {
      for (PetscInt c = 0; c < dof; c++) garray[j][i][c] = (larray[j][i - 1][c] + larray[j][i + 1][c] + larray[j - 1][i][c] + larray[j + 1][i][c]) / 4.0;
    }
  }
  PetscCall(DMDAVecRestoreArrayDOFWrite(da, g, &garray));
  PetscCall(DMDAVecRestoreArrayDOFRead(da, l, &larray));

  /* Do stencil on gg with values from ll that contains ghosts */
  PetscCall(DMDAVecGetKokkosOffsetViewDOFWrite(da, gg, &gview));
  PetscCall(DMDAVecGetKokkosOffsetViewDOF(da, ll, &lview));
  Kokkos::parallel_for(
    "stencil 1", MDRangePolicy<Rank<3, Iterate::Right, Iterate::Right>>({ys, xs, 0}, {ys + ym, xs + xm, dof}),
    KOKKOS_LAMBDA(PetscInt j, PetscInt i, PetscInt c) { gview(j, i, c) = (lview(j, i - 1, c) + lview(j, i + 1, c) + lview(j - 1, i, c) + lview(j + 1, i, c)) / 4.0; });
  PetscCall(DMDAVecRestoreKokkosOffsetViewDOFWrite(da, gg, &gview));
  PetscCall(DMDAVecRestoreKokkosOffsetViewDOF(da, ll, &lview));

  /* gg should be equal to g */
  PetscCall(VecAXPY(g, -1.0, gg));
  PetscCall(VecNorm(g, NORM_2, &nrm));
  PetscCheck(nrm < PETSC_SMALL, PETSC_COMM_WORLD, PETSC_ERR_PLIB, "gg is not equal to g");

  PetscCall(DMDestroy(&da));
  PetscCall(VecDestroy(&l));
  PetscCall(VecDestroy(&g));
  PetscCall(VecDestroy(&ll));
  PetscCall(VecDestroy(&gg));

  /* =============================================================================
    Show how to manage a multi-component DMDA using DMDAVecGetKokkosOffsetView and
    a customized struct type
   ==============================================================================*/
  Node                             **garray2; /* Node arrays of g, l */
  const Node                       **larray2;
  PetscScalarKokkosOffsetView2D      gview2; /* PetscScalar views of gg, ll */
  ConstPetscScalarKokkosOffsetView2D lview2;
  NodeKokkosOffsetView2D             gnview; /* Node views of gg, ll */
  ConstNodeKokkosOffsetView2D        lnview;

  dof = sizeof(Node) / sizeof(PetscScalar);
  PetscCall(DMDACreate2d(PETSC_COMM_WORLD, bx, by, st, M, N, PETSC_DECIDE, PETSC_DECIDE, sizeof(Node) / sizeof(PetscScalar), sw, NULL, NULL, &da));
  PetscCall(DMSetFromOptions(da));
  PetscCall(DMSetUp(da));
  PetscCall(DMDAGetCorners(da, &xs, &ys, 0, &xm, &ym, 0));
  PetscCall(DMCreateGlobalVector(da, &g));
  PetscCall(DMCreateLocalVector(da, &l));
  PetscCall(DMCreateGlobalVector(da, &gg));
  PetscCall(DMCreateLocalVector(da, &ll));

  /* Init g using array */
  PetscCall(DMDAVecGetArrayWrite(da, g, &garray2));
  for (PetscInt j = ys; j < ys + ym; j++) {
    for (PetscInt i = xs; i < xs + xm; i++) {
      garray2[j][i].u = 100 * j + 10 * (i + 1) + 111;
      garray2[j][i].v = 100 * j + 10 * (i + 1) + 222;
      garray2[j][i].w = 100 * j + 10 * (i + 1) + 333;
    }
  }
  PetscCall(DMDAVecRestoreArrayWrite(da, g, &garray2));

  /* Init gg using view */
  PetscCall(DMDAVecGetKokkosOffsetViewWrite(da, gg, &gview2));
  gnview = NodeKokkosOffsetView2D(reinterpret_cast<Node *>(gview2.data()), {gview2.begin(0) / dof, gview2.begin(1) / dof}, {gview2.end(0) / dof, gview2.end(1) / dof});
  Kokkos::parallel_for(
    "init 2", MDRangePolicy<Rank<2, Iterate::Right, Iterate::Right>>({ys, xs}, {ys + ym, xs + xm}), KOKKOS_LAMBDA(PetscInt j, PetscInt i) {
      gnview(j, i).u = 100 * j + 10 * (i + 1) + 111;
      gnview(j, i).v = 100 * j + 10 * (i + 1) + 222;
      gnview(j, i).w = 100 * j + 10 * (i + 1) + 333;
    });
  PetscCall(DMDAVecRestoreKokkosOffsetViewWrite(da, gg, &gview2));

  /* Scatter g, gg to l, ll */
  PetscCall(DMGlobalToLocal(da, g, INSERT_VALUES, l));
  PetscCall(DMGlobalToLocal(da, gg, INSERT_VALUES, ll));

  /* Do stencil on g with values from l that contains ghosts */
  PetscCall(DMDAVecGetArrayWrite(da, g, &garray2));
  PetscCall(DMDAVecGetArray(da, l, &larray2));
  for (PetscInt j = ys; j < ys + ym; j++) {
    for (PetscInt i = xs; i < xs + xm; i++) {
      garray2[j][i].u = (larray2[j][i - 1].u + larray2[j][i + 1].u + larray2[j - 1][i].u + larray2[j + 1][i].u) / 4.0;
      garray2[j][i].v = (larray2[j][i - 1].v + larray2[j][i + 1].v + larray2[j - 1][i].v + larray2[j + 1][i].v) / 4.0;
      garray2[j][i].w = (larray2[j][i - 1].w + larray2[j][i + 1].w + larray2[j - 1][i].w + larray2[j + 1][i].w) / 4.0;
    }
  }
  PetscCall(DMDAVecRestoreArrayWrite(da, g, &garray2));
  PetscCall(DMDAVecRestoreArray(da, l, &larray2));

  /* Do stencil on gg with values from ll that contains ghosts */
  PetscCall(DMDAVecGetKokkosOffsetViewWrite(da, gg, &gview2)); /* write-only */
  PetscCall(DMDAVecGetKokkosOffsetView(da, ll, &lview2));      /* read-only */
  gnview = NodeKokkosOffsetView2D(reinterpret_cast<Node *>(gview2.data()), {gview2.begin(0) / dof, gview2.begin(1) / dof}, {gview2.end(0) / dof, gview2.end(1) / dof});
  lnview = ConstNodeKokkosOffsetView2D(reinterpret_cast<const Node *>(lview2.data()), {lview2.begin(0) / dof, lview2.begin(1) / dof}, {lview2.end(0) / dof, lview2.end(1) / dof});
  Kokkos::parallel_for(
    "stencil 2", MDRangePolicy<Rank<2, Iterate::Right, Iterate::Right>>({ys, xs}, {ys + ym, xs + xm}), KOKKOS_LAMBDA(PetscInt j, PetscInt i) {
      gnview(j, i).u = (lnview(j, i - 1).u + lnview(j, i + 1).u + lnview(j - 1, i).u + lnview(j + 1, i).u) / 4.0;
      gnview(j, i).v = (lnview(j, i - 1).v + lnview(j, i + 1).v + lnview(j - 1, i).v + lnview(j + 1, i).v) / 4.0;
      gnview(j, i).w = (lnview(j, i - 1).w + lnview(j, i + 1).w + lnview(j - 1, i).w + lnview(j + 1, i).w) / 4.0;
    });
  PetscCall(DMDAVecRestoreKokkosOffsetViewWrite(da, gg, &gview2));
  PetscCall(DMDAVecRestoreKokkosOffsetView(da, ll, &lview2));

  /* gg should be equal to g */
  PetscCall(VecAXPY(g, -1.0, gg));
  PetscCall(VecNorm(g, NORM_2, &nrm));
  PetscCheck(nrm < PETSC_SMALL, PETSC_COMM_WORLD, PETSC_ERR_PLIB, "gg is not equal to g");

  PetscCall(DMDestroy(&da));
  PetscCall(VecDestroy(&l));
  PetscCall(VecDestroy(&g));
  PetscCall(VecDestroy(&ll));
  PetscCall(VecDestroy(&gg));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST
  build:
    requires: kokkos_kernels

  test:
    suffix: 1
    nsize: 4
    requires: kokkos_kernels
    args: -dm_vec_type kokkos
    output_file: output/empty.out

TEST*/