#include <petsc/private/sfimpl.h>
#include <../src/vec/is/sf/impls/basic/sfpack.h>
#include <../src/vec/is/sf/impls/basic/sfbasic.h>

/* This is a C file that contains packing facilities, with dispatches to device if enabled. */

/*
 * MPI_Reduce_local is not really useful because it can't handle sparse data and it vectorizes "in the wrong direction",
 * therefore we pack data types manually. This file defines packing routines for the standard data types.
 */

#define CPPJoin4(a, b, c, d) a##_##b##_##c##_##d

/* Operations working like s += t */
#define OP_BINARY(op, s, t) \
  do { \
    (s) = (s)op(t); \
  } while (0) /* binary ops in the middle such as +, *, && etc. */
#define OP_FUNCTION(op, s, t) \
  do { \
    (s) = op((s), (t)); \
  } while (0) /* ops like a function, such as PetscMax, PetscMin */
#define OP_LXOR(op, s, t) \
  do { \
    (s) = (!(s)) != (!(t)); \
  } while (0) /* logical exclusive OR */
#define OP_ASSIGN(op, s, t) \
  do { \
    (s) = (t); \
  } while (0)
/* Ref MPI MAXLOC */
#define OP_XLOC(op, s, t) \
  do { \
    if ((s).u == (t).u) (s).i = PetscMin((s).i, (t).i); \
    else if (!((s).u op(t).u)) s = t; \
  } while (0)

/* DEF_PackFunc - macro defining a Pack routine

   Arguments of the macro:
   +Type      Type of the basic data in an entry, i.e., int, PetscInt, PetscReal etc. It is not the type of an entry.
   .BS        Block size for vectorization. It is a factor of bsz.
   -EQ        (bs == BS) ? 1 : 0. EQ is a compile-time const to help compiler optimizations. See below.

   Arguments of the Pack routine:
   +count     Number of indices in idx[].
   .start     When opt and idx are NULL, it means indices are contiguous & start is the first index; otherwise, not used.
   .opt       Per-pack optimization plan. NULL means no such plan.
   .idx       Indices of entries to packed.
   .link      Provide a context for the current call, such as link->bs, number of basic types in an entry. Ex. if unit is MPI_2INT, then bs=2 and the basic type is int.
   .unpacked  Address of the unpacked data. The entries will be packed are unpacked[idx[i]],for i in [0,count).
   -packed    Address of the packed data.
 */
#define DEF_PackFunc(Type, BS, EQ) \
  static PetscErrorCode CPPJoin4(Pack, Type, BS, EQ)(PetscSFLink link, PetscInt count, PetscInt start, PetscSFPackOpt opt, const PetscInt *idx, const void *unpacked, void *packed) \
  { \
    const Type    *u = (const Type *)unpacked, *u2; \
    Type          *p = (Type *)packed, *p2; \
    PetscInt       i, j, k, X, Y, r, bs = link->bs; \
    const PetscInt M   = (EQ) ? 1 : bs / BS; /* If EQ, then M=1 enables compiler's const-propagation */ \
    const PetscInt MBS = M * BS;             /* MBS=bs. We turn MBS into a compile time const when EQ=1. */ \
    PetscFunctionBegin; \
    if (!idx) PetscCall(PetscArraycpy(p, u + start * MBS, MBS * count)); /* idx[] are contiguous */ \
    else if (opt) { /* has optimizations available */ p2 = p; \
      for (r = 0; r < opt->n; r++) { \
        u2 = u + opt->start[r] * MBS; \
        X  = opt->X[r]; \
        Y  = opt->Y[r]; \
        for (k = 0; k < opt->dz[r]; k++) \
          for (j = 0; j < opt->dy[r]; j++) { \
            PetscCall(PetscArraycpy(p2, u2 + (X * Y * k + X * j) * MBS, opt->dx[r] * MBS)); \
            p2 += opt->dx[r] * MBS; \
          } \
      } \
    } else { \
      for (i = 0; i < count; i++) \
        for (j = 0; j < M; j++)    /* Decent compilers should eliminate this loop when M = const 1 */ \
          for (k = 0; k < BS; k++) /* Compiler either unrolls (BS=1) or vectorizes (BS=2,4,8,etc) this loop */ \
            p[i * MBS + j * BS + k] = u[idx[i] * MBS + j * BS + k]; \
    } \
    PetscFunctionReturn(PETSC_SUCCESS); \
  }

/* DEF_Action - macro defining a UnpackAndInsert routine that unpacks data from a contiguous buffer
                and inserts into a sparse array.

   Arguments:
  .Type       Type of the data
  .BS         Block size for vectorization
  .EQ        (bs == BS) ? 1 : 0. EQ is a compile-time const.

  Notes:
   This macro is not combined with DEF_ActionAndOp because we want to use memcpy in this macro.
 */
#define DEF_UnpackFunc(Type, BS, EQ) \
  static PetscErrorCode CPPJoin4(UnpackAndInsert, Type, BS, EQ)(PetscSFLink link, PetscInt count, PetscInt start, PetscSFPackOpt opt, const PetscInt *idx, void *unpacked, const void *packed) \
  { \
    Type          *u = (Type *)unpacked, *u2; \
    const Type    *p = (const Type *)packed; \
    PetscInt       i, j, k, X, Y, r, bs = link->bs; \
    const PetscInt M   = (EQ) ? 1 : bs / BS; /* If EQ, then M=1 enables compiler's const-propagation */ \
    const PetscInt MBS = M * BS;             /* MBS=bs. We turn MBS into a compile time const when EQ=1. */ \
    PetscFunctionBegin; \
    if (!idx) { \
      u += start * MBS; \
      if (u != p) PetscCall(PetscArraycpy(u, p, count *MBS)); \
    } else if (opt) { /* has optimizations available */ \
      for (r = 0; r < opt->n; r++) { \
        u2 = u + opt->start[r] * MBS; \
        X  = opt->X[r]; \
        Y  = opt->Y[r]; \
        for (k = 0; k < opt->dz[r]; k++) \
          for (j = 0; j < opt->dy[r]; j++) { \
            PetscCall(PetscArraycpy(u2 + (X * Y * k + X * j) * MBS, p, opt->dx[r] * MBS)); \
            p += opt->dx[r] * MBS; \
          } \
      } \
    } else { \
      for (i = 0; i < count; i++) \
        for (j = 0; j < M; j++) \
          for (k = 0; k < BS; k++) u[idx[i] * MBS + j * BS + k] = p[i * MBS + j * BS + k]; \
    } \
    PetscFunctionReturn(PETSC_SUCCESS); \
  }

/* DEF_UnpackAndOp - macro defining a UnpackAndOp routine where Op should not be Insert

   Arguments:
  +Opname     Name of the Op, such as Add, Mult, LAND, etc.
  .Type       Type of the data
  .BS         Block size for vectorization
  .EQ         (bs == BS) ? 1 : 0. EQ is a compile-time const.
  .Op         Operator for the op, such as +, *, &&, ||, PetscMax, PetscMin, etc.
  .OpApply    Macro defining application of the op. Could be OP_BINARY, OP_FUNCTION, OP_LXOR
 */
#define DEF_UnpackAndOp(Type, BS, EQ, Opname, Op, OpApply) \
  static PetscErrorCode CPPJoin4(UnpackAnd##Opname, Type, BS, EQ)(PetscSFLink link, PetscInt count, PetscInt start, PetscSFPackOpt opt, const PetscInt *idx, void *unpacked, const void *packed) \
  { \
    Type          *u = (Type *)unpacked, *u2; \
    const Type    *p = (const Type *)packed; \
    PetscInt       i, j, k, X, Y, r, bs = link->bs; \
    const PetscInt M   = (EQ) ? 1 : bs / BS; /* If EQ, then M=1 enables compiler's const-propagation */ \
    const PetscInt MBS = M * BS;             /* MBS=bs. We turn MBS into a compile time const when EQ=1. */ \
    PetscFunctionBegin; \
    if (!idx) { \
      u += start * MBS; \
      for (i = 0; i < count; i++) \
        for (j = 0; j < M; j++) \
          for (k = 0; k < BS; k++) OpApply(Op, u[i * MBS + j * BS + k], p[i * MBS + j * BS + k]); \
    } else if (opt) { /* idx[] has patterns */ \
      for (r = 0; r < opt->n; r++) { \
        u2 = u + opt->start[r] * MBS; \
        X  = opt->X[r]; \
        Y  = opt->Y[r]; \
        for (k = 0; k < opt->dz[r]; k++) \
          for (j = 0; j < opt->dy[r]; j++) { \
            for (i = 0; i < opt->dx[r] * MBS; i++) OpApply(Op, u2[(X * Y * k + X * j) * MBS + i], p[i]); \
            p += opt->dx[r] * MBS; \
          } \
      } \
    } else { \
      for (i = 0; i < count; i++) \
        for (j = 0; j < M; j++) \
          for (k = 0; k < BS; k++) OpApply(Op, u[idx[i] * MBS + j * BS + k], p[i * MBS + j * BS + k]); \
    } \
    PetscFunctionReturn(PETSC_SUCCESS); \
  }

#define DEF_FetchAndOp(Type, BS, EQ, Opname, Op, OpApply) \
  static PetscErrorCode CPPJoin4(FetchAnd##Opname, Type, BS, EQ)(PetscSFLink link, PetscInt count, PetscInt start, PetscSFPackOpt opt, const PetscInt *idx, void *unpacked, void *packed) \
  { \
    Type          *u = (Type *)unpacked, *p = (Type *)packed, tmp; \
    PetscInt       i, j, k, r, l, bs = link->bs; \
    const PetscInt M   = (EQ) ? 1 : bs / BS; \
    const PetscInt MBS = M * BS; \
    PetscFunctionBegin; \
    for (i = 0; i < count; i++) { \
      r = (!idx ? start + i : idx[i]) * MBS; \
      l = i * MBS; \
      for (j = 0; j < M; j++) \
        for (k = 0; k < BS; k++) { \
          tmp = u[r + j * BS + k]; \
          OpApply(Op, u[r + j * BS + k], p[l + j * BS + k]); \
          p[l + j * BS + k] = tmp; \
        } \
    } \
    PetscFunctionReturn(PETSC_SUCCESS); \
  }

#define DEF_ScatterAndOp(Type, BS, EQ, Opname, Op, OpApply) \
  static PetscErrorCode CPPJoin4(ScatterAnd##Opname, Type, BS, EQ)(PetscSFLink link, PetscInt count, PetscInt srcStart, PetscSFPackOpt srcOpt, const PetscInt *srcIdx, const void *src, PetscInt dstStart, PetscSFPackOpt dstOpt, const PetscInt *dstIdx, void *dst) \
  { \
    const Type    *u = (const Type *)src; \
    Type          *v = (Type *)dst; \
    PetscInt       i, j, k, s, t, X, Y, bs = link->bs; \
    const PetscInt M   = (EQ) ? 1 : bs / BS; \
    const PetscInt MBS = M * BS; \
    PetscFunctionBegin; \
    if (!srcIdx) { /* src is contiguous */ \
      u += srcStart * MBS; \
      PetscCall(CPPJoin4(UnpackAnd##Opname, Type, BS, EQ)(link, count, dstStart, dstOpt, dstIdx, dst, u)); \
    } else if (srcOpt && !dstIdx) { /* src is 3D, dst is contiguous */ \
      u += srcOpt->start[0] * MBS; \
      v += dstStart * MBS; \
      X = srcOpt->X[0]; \
      Y = srcOpt->Y[0]; \
      for (k = 0; k < srcOpt->dz[0]; k++) \
        for (j = 0; j < srcOpt->dy[0]; j++) { \
          for (i = 0; i < srcOpt->dx[0] * MBS; i++) OpApply(Op, v[i], u[(X * Y * k + X * j) * MBS + i]); \
          v += srcOpt->dx[0] * MBS; \
        } \
    } else { /* all other cases */ \
      for (i = 0; i < count; i++) { \
        s = (!srcIdx ? srcStart + i : srcIdx[i]) * MBS; \
        t = (!dstIdx ? dstStart + i : dstIdx[i]) * MBS; \
        for (j = 0; j < M; j++) \
          for (k = 0; k < BS; k++) OpApply(Op, v[t + j * BS + k], u[s + j * BS + k]); \
      } \
    } \
    PetscFunctionReturn(PETSC_SUCCESS); \
  }

#define DEF_FetchAndOpLocal(Type, BS, EQ, Opname, Op, OpApply) \
  static PetscErrorCode CPPJoin4(FetchAnd##Opname##Local, Type, BS, EQ)(PetscSFLink link, PetscInt count, PetscInt rootstart, PetscSFPackOpt rootopt, const PetscInt *rootidx, void *rootdata, PetscInt leafstart, PetscSFPackOpt leafopt, const PetscInt *leafidx, const void *leafdata, void *leafupdate) \
  { \
    Type          *rdata = (Type *)rootdata, *lupdate = (Type *)leafupdate; \
    const Type    *ldata = (const Type *)leafdata; \
    PetscInt       i, j, k, r, l, bs = link->bs; \
    const PetscInt M   = (EQ) ? 1 : bs / BS; \
    const PetscInt MBS = M * BS; \
    PetscFunctionBegin; \
    for (i = 0; i < count; i++) { \
      r = (rootidx ? rootidx[i] : rootstart + i) * MBS; \
      l = (leafidx ? leafidx[i] : leafstart + i) * MBS; \
      for (j = 0; j < M; j++) \
        for (k = 0; k < BS; k++) { \
          lupdate[l + j * BS + k] = rdata[r + j * BS + k]; \
          OpApply(Op, rdata[r + j * BS + k], ldata[l + j * BS + k]); \
        } \
    } \
    PetscFunctionReturn(PETSC_SUCCESS); \
  }

/* Pack, Unpack/Fetch ops */
#define DEF_Pack(Type, BS, EQ) \
  DEF_PackFunc(Type, BS, EQ) DEF_UnpackFunc(Type, BS, EQ) DEF_ScatterAndOp(Type, BS, EQ, Insert, =, OP_ASSIGN) static void CPPJoin4(PackInit_Pack, Type, BS, EQ)(PetscSFLink link) \
  { \
    link->h_Pack             = CPPJoin4(Pack, Type, BS, EQ); \
    link->h_UnpackAndInsert  = CPPJoin4(UnpackAndInsert, Type, BS, EQ); \
    link->h_ScatterAndInsert = CPPJoin4(ScatterAndInsert, Type, BS, EQ); \
  }

/* Add, Mult ops */
#define DEF_Add(Type, BS, EQ) \
  DEF_UnpackAndOp(Type, BS, EQ, Add, +, OP_BINARY) DEF_UnpackAndOp(Type, BS, EQ, Mult, *, OP_BINARY) DEF_FetchAndOp(Type, BS, EQ, Add, +, OP_BINARY) DEF_ScatterAndOp(Type, BS, EQ, Add, +, OP_BINARY) DEF_ScatterAndOp(Type, BS, EQ, Mult, *, OP_BINARY) DEF_FetchAndOpLocal(Type, BS, EQ, Add, +, OP_BINARY) static void CPPJoin4(PackInit_Add, Type, BS, EQ)(PetscSFLink link) \
  { \
    link->h_UnpackAndAdd     = CPPJoin4(UnpackAndAdd, Type, BS, EQ); \
    link->h_UnpackAndMult    = CPPJoin4(UnpackAndMult, Type, BS, EQ); \
    link->h_FetchAndAdd      = CPPJoin4(FetchAndAdd, Type, BS, EQ); \
    link->h_ScatterAndAdd    = CPPJoin4(ScatterAndAdd, Type, BS, EQ); \
    link->h_ScatterAndMult   = CPPJoin4(ScatterAndMult, Type, BS, EQ); \
    link->h_FetchAndAddLocal = CPPJoin4(FetchAndAddLocal, Type, BS, EQ); \
  }

/* Max, Min ops */
#define DEF_Cmp(Type, BS, EQ) \
  DEF_UnpackAndOp(Type, BS, EQ, Max, PetscMax, OP_FUNCTION) DEF_UnpackAndOp(Type, BS, EQ, Min, PetscMin, OP_FUNCTION) DEF_ScatterAndOp(Type, BS, EQ, Max, PetscMax, OP_FUNCTION) DEF_ScatterAndOp(Type, BS, EQ, Min, PetscMin, OP_FUNCTION) static void CPPJoin4(PackInit_Compare, Type, BS, EQ)(PetscSFLink link) \
  { \
    link->h_UnpackAndMax  = CPPJoin4(UnpackAndMax, Type, BS, EQ); \
    link->h_UnpackAndMin  = CPPJoin4(UnpackAndMin, Type, BS, EQ); \
    link->h_ScatterAndMax = CPPJoin4(ScatterAndMax, Type, BS, EQ); \
    link->h_ScatterAndMin = CPPJoin4(ScatterAndMin, Type, BS, EQ); \
  }

/* Logical ops.
  The operator in OP_LXOR should be empty but is ||. It is not used. Put here to avoid
  the compilation warning "empty macro arguments are undefined in ISO C90"
 */
#define DEF_Log(Type, BS, EQ) \
  DEF_UnpackAndOp(Type, BS, EQ, LAND, &&, OP_BINARY) DEF_UnpackAndOp(Type, BS, EQ, LOR, ||, OP_BINARY) DEF_UnpackAndOp(Type, BS, EQ, LXOR, ||, OP_LXOR) DEF_ScatterAndOp(Type, BS, EQ, LAND, &&, OP_BINARY) DEF_ScatterAndOp(Type, BS, EQ, LOR, ||, OP_BINARY) DEF_ScatterAndOp(Type, BS, EQ, LXOR, ||, OP_LXOR) static void CPPJoin4(PackInit_Logical, Type, BS, EQ)(PetscSFLink link) \
  { \
    link->h_UnpackAndLAND  = CPPJoin4(UnpackAndLAND, Type, BS, EQ); \
    link->h_UnpackAndLOR   = CPPJoin4(UnpackAndLOR, Type, BS, EQ); \
    link->h_UnpackAndLXOR  = CPPJoin4(UnpackAndLXOR, Type, BS, EQ); \
    link->h_ScatterAndLAND = CPPJoin4(ScatterAndLAND, Type, BS, EQ); \
    link->h_ScatterAndLOR  = CPPJoin4(ScatterAndLOR, Type, BS, EQ); \
    link->h_ScatterAndLXOR = CPPJoin4(ScatterAndLXOR, Type, BS, EQ); \
  }

/* Bitwise ops */
#define DEF_Bit(Type, BS, EQ) \
  DEF_UnpackAndOp(Type, BS, EQ, BAND, &, OP_BINARY) DEF_UnpackAndOp(Type, BS, EQ, BOR, |, OP_BINARY) DEF_UnpackAndOp(Type, BS, EQ, BXOR, ^, OP_BINARY) DEF_ScatterAndOp(Type, BS, EQ, BAND, &, OP_BINARY) DEF_ScatterAndOp(Type, BS, EQ, BOR, |, OP_BINARY) DEF_ScatterAndOp(Type, BS, EQ, BXOR, ^, OP_BINARY) static void CPPJoin4(PackInit_Bitwise, Type, BS, EQ)(PetscSFLink link) \
  { \
    link->h_UnpackAndBAND  = CPPJoin4(UnpackAndBAND, Type, BS, EQ); \
    link->h_UnpackAndBOR   = CPPJoin4(UnpackAndBOR, Type, BS, EQ); \
    link->h_UnpackAndBXOR  = CPPJoin4(UnpackAndBXOR, Type, BS, EQ); \
    link->h_ScatterAndBAND = CPPJoin4(ScatterAndBAND, Type, BS, EQ); \
    link->h_ScatterAndBOR  = CPPJoin4(ScatterAndBOR, Type, BS, EQ); \
    link->h_ScatterAndBXOR = CPPJoin4(ScatterAndBXOR, Type, BS, EQ); \
  }

/* Maxloc, Minloc ops */
#define DEF_Xloc(Type, BS, EQ) \
  DEF_UnpackAndOp(Type, BS, EQ, Max, >, OP_XLOC) DEF_UnpackAndOp(Type, BS, EQ, Min, <, OP_XLOC) DEF_ScatterAndOp(Type, BS, EQ, Max, >, OP_XLOC) DEF_ScatterAndOp(Type, BS, EQ, Min, <, OP_XLOC) static void CPPJoin4(PackInit_Xloc, Type, BS, EQ)(PetscSFLink link) \
  { \
    link->h_UnpackAndMaxloc  = CPPJoin4(UnpackAndMax, Type, BS, EQ); \
    link->h_UnpackAndMinloc  = CPPJoin4(UnpackAndMin, Type, BS, EQ); \
    link->h_ScatterAndMaxloc = CPPJoin4(ScatterAndMax, Type, BS, EQ); \
    link->h_ScatterAndMinloc = CPPJoin4(ScatterAndMin, Type, BS, EQ); \
  }

#define DEF_IntegerType(Type, BS, EQ) \
  DEF_Pack(Type, BS, EQ) DEF_Add(Type, BS, EQ) DEF_Cmp(Type, BS, EQ) DEF_Log(Type, BS, EQ) DEF_Bit(Type, BS, EQ) static void CPPJoin4(PackInit_IntegerType, Type, BS, EQ)(PetscSFLink link) \
  { \
    CPPJoin4(PackInit_Pack, Type, BS, EQ)(link); \
    CPPJoin4(PackInit_Add, Type, BS, EQ)(link); \
    CPPJoin4(PackInit_Compare, Type, BS, EQ)(link); \
    CPPJoin4(PackInit_Logical, Type, BS, EQ)(link); \
    CPPJoin4(PackInit_Bitwise, Type, BS, EQ)(link); \
  }

#define DEF_RealType(Type, BS, EQ) \
  DEF_Pack(Type, BS, EQ) DEF_Add(Type, BS, EQ) DEF_Cmp(Type, BS, EQ) static void CPPJoin4(PackInit_RealType, Type, BS, EQ)(PetscSFLink link) \
  { \
    CPPJoin4(PackInit_Pack, Type, BS, EQ)(link); \
    CPPJoin4(PackInit_Add, Type, BS, EQ)(link); \
    CPPJoin4(PackInit_Compare, Type, BS, EQ)(link); \
  }

#if defined(PETSC_HAVE_COMPLEX)
  #define DEF_ComplexType(Type, BS, EQ) \
    DEF_Pack(Type, BS, EQ) DEF_Add(Type, BS, EQ) static void CPPJoin4(PackInit_ComplexType, Type, BS, EQ)(PetscSFLink link) \
    { \
      CPPJoin4(PackInit_Pack, Type, BS, EQ)(link); \
      CPPJoin4(PackInit_Add, Type, BS, EQ)(link); \
    }
#endif

#define DEF_DumbType(Type, BS, EQ) \
  DEF_Pack(Type, BS, EQ) static void CPPJoin4(PackInit_DumbType, Type, BS, EQ)(PetscSFLink link) \
  { \
    CPPJoin4(PackInit_Pack, Type, BS, EQ)(link); \
  }

/* Maxloc, Minloc */
#define DEF_PairType(Type, BS, EQ) \
  DEF_Pack(Type, BS, EQ) DEF_Xloc(Type, BS, EQ) static void CPPJoin4(PackInit_PairType, Type, BS, EQ)(PetscSFLink link) \
  { \
    CPPJoin4(PackInit_Pack, Type, BS, EQ)(link); \
    CPPJoin4(PackInit_Xloc, Type, BS, EQ)(link); \
  }

DEF_IntegerType(PetscInt, 1, 1)   /* unit = 1 MPIU_INT  */
  DEF_IntegerType(PetscInt, 2, 1) /* unit = 2 MPIU_INTs */
  DEF_IntegerType(PetscInt, 4, 1) /* unit = 4 MPIU_INTs */
  DEF_IntegerType(PetscInt, 8, 1) /* unit = 8 MPIU_INTs */
  DEF_IntegerType(PetscInt, 1, 0) /* unit = 1*n MPIU_INTs, n>1 */
  DEF_IntegerType(PetscInt, 2, 0) /* unit = 2*n MPIU_INTs, n>1 */
  DEF_IntegerType(PetscInt, 4, 0) /* unit = 4*n MPIU_INTs, n>1 */
  DEF_IntegerType(PetscInt, 8, 0) /* unit = 8*n MPIU_INTs, n>1. Routines with bigger BS are tried first. */

#if defined(PETSC_USE_64BIT_INDICES) /* Do not need (though it is OK) to generate redundant functions if PetscInt is int */
  DEF_IntegerType(int, 1, 1) DEF_IntegerType(int, 2, 1) DEF_IntegerType(int, 4, 1) DEF_IntegerType(int, 8, 1) DEF_IntegerType(int, 1, 0) DEF_IntegerType(int, 2, 0) DEF_IntegerType(int, 4, 0) DEF_IntegerType(int, 8, 0)
#endif

  /* The typedefs are used to get a typename without space that CPPJoin can handle */
  typedef signed char SignedChar;
DEF_IntegerType(SignedChar, 1, 1) DEF_IntegerType(SignedChar, 2, 1) DEF_IntegerType(SignedChar, 4, 1) DEF_IntegerType(SignedChar, 8, 1) DEF_IntegerType(SignedChar, 1, 0) DEF_IntegerType(SignedChar, 2, 0) DEF_IntegerType(SignedChar, 4, 0) DEF_IntegerType(SignedChar, 8, 0)

  typedef unsigned char UnsignedChar;
DEF_IntegerType(UnsignedChar, 1, 1) DEF_IntegerType(UnsignedChar, 2, 1) DEF_IntegerType(UnsignedChar, 4, 1) DEF_IntegerType(UnsignedChar, 8, 1) DEF_IntegerType(UnsignedChar, 1, 0) DEF_IntegerType(UnsignedChar, 2, 0) DEF_IntegerType(UnsignedChar, 4, 0) DEF_IntegerType(UnsignedChar, 8, 0)

  DEF_RealType(PetscReal, 1, 1) DEF_RealType(PetscReal, 2, 1) DEF_RealType(PetscReal, 4, 1) DEF_RealType(PetscReal, 8, 1) DEF_RealType(PetscReal, 1, 0) DEF_RealType(PetscReal, 2, 0) DEF_RealType(PetscReal, 4, 0) DEF_RealType(PetscReal, 8, 0)
#if defined(PETSC_HAVE_COMPLEX)
    DEF_ComplexType(PetscComplex, 1, 1) DEF_ComplexType(PetscComplex, 2, 1) DEF_ComplexType(PetscComplex, 4, 1) DEF_ComplexType(PetscComplex, 8, 1) DEF_ComplexType(PetscComplex, 1, 0) DEF_ComplexType(PetscComplex, 2, 0) DEF_ComplexType(PetscComplex, 4, 0) DEF_ComplexType(PetscComplex, 8, 0)
#endif

#define PairType(Type1, Type2) Type1##_##Type2
      typedef struct {
  int u;
  int i;
} PairType(int, int);
typedef struct {
  PetscInt u;
  PetscInt i;
} PairType(PetscInt, PetscInt);
DEF_PairType(PairType(int, int), 1, 1) DEF_PairType(PairType(PetscInt, PetscInt), 1, 1)

  /* If we don't know the basic type, we treat it as a stream of chars or ints */
  DEF_DumbType(char, 1, 1) DEF_DumbType(char, 2, 1) DEF_DumbType(char, 4, 1) DEF_DumbType(char, 1, 0) DEF_DumbType(char, 2, 0) DEF_DumbType(char, 4, 0)

    typedef int DumbInt; /* To have a different name than 'int' used above. The name is used to make routine names. */
DEF_DumbType(DumbInt, 1, 1) DEF_DumbType(DumbInt, 2, 1) DEF_DumbType(DumbInt, 4, 1) DEF_DumbType(DumbInt, 8, 1) DEF_DumbType(DumbInt, 1, 0) DEF_DumbType(DumbInt, 2, 0) DEF_DumbType(DumbInt, 4, 0) DEF_DumbType(DumbInt, 8, 0)

  PetscErrorCode PetscSFLinkDestroy(PetscSF sf, PetscSFLink link)
{
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;
  PetscInt       i, nreqs = (bas->nrootreqs + sf->nleafreqs) * 8;

  PetscFunctionBegin;
  /* Destroy device-specific fields */
  if (link->deviceinited) PetscCall((*link->Destroy)(sf, link));

  /* Destroy host related fields */
  if (!link->isbuiltin) PetscCallMPI(MPI_Type_free(&link->unit));
  if (!link->use_nvshmem) {
    for (i = 0; i < nreqs; i++) { /* Persistent reqs must be freed. */
      if (link->reqs[i] != MPI_REQUEST_NULL) PetscCallMPI(MPI_Request_free(&link->reqs[i]));
    }
    PetscCall(PetscFree(link->reqs));
    for (i = PETSCSF_LOCAL; i <= PETSCSF_REMOTE; i++) {
      PetscCall(PetscFree(link->rootbuf_alloc[i][PETSC_MEMTYPE_HOST]));
      PetscCall(PetscFree(link->leafbuf_alloc[i][PETSC_MEMTYPE_HOST]));
    }
  }
  PetscCall(PetscFree(link));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkCreate(PetscSF sf, MPI_Datatype unit, PetscMemType rootmtype, const void *rootdata, PetscMemType leafmtype, const void *leafdata, MPI_Op op, PetscSFOperation sfop, PetscSFLink *mylink)
{
  PetscFunctionBegin;
  PetscCall(PetscSFSetErrorOnUnsupportedOverlap(sf, unit, rootdata, leafdata));
#if defined(PETSC_HAVE_NVSHMEM)
  {
    PetscBool use_nvshmem;
    PetscCall(PetscSFLinkNvshmemCheck(sf, rootmtype, rootdata, leafmtype, leafdata, &use_nvshmem));
    if (use_nvshmem) {
      PetscCall(PetscSFLinkCreate_NVSHMEM(sf, unit, rootmtype, rootdata, leafmtype, leafdata, op, sfop, mylink));
      PetscFunctionReturn(PETSC_SUCCESS);
    }
  }
#endif
  PetscCall(PetscSFLinkCreate_MPI(sf, unit, rootmtype, rootdata, leafmtype, leafdata, op, sfop, mylink));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkGetInUse(PetscSF sf, MPI_Datatype unit, const void *rootdata, const void *leafdata, PetscCopyMode cmode, PetscSFLink *mylink)
{
  PetscSFLink    link, *p;
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;

  PetscFunctionBegin;
  /* Look for types in cache */
  for (p = &bas->inuse; (link = *p); p = &link->next) {
    PetscBool match;
    PetscCall(MPIPetsc_Type_compare(unit, link->unit, &match));
    if (match && (rootdata == link->rootdata) && (leafdata == link->leafdata)) {
      switch (cmode) {
      case PETSC_OWN_POINTER:
        *p = link->next;
        break; /* Remove from inuse list */
      case PETSC_USE_POINTER:
        break;
      default:
        SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "invalid cmode");
      }
      *mylink = link;
      PetscFunctionReturn(PETSC_SUCCESS);
    }
  }
  SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Could not find pack");
}

PetscErrorCode PetscSFLinkReclaim(PetscSF sf, PetscSFLink *mylink)
{
  PetscSF_Basic *bas  = (PetscSF_Basic *)sf->data;
  PetscSFLink    link = *mylink;

  PetscFunctionBegin;
  link->rootdata = NULL;
  link->leafdata = NULL;
  link->next     = bas->avail;
  bas->avail     = link;
  *mylink        = NULL;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/* Error out on unsupported overlapped communications */
PetscErrorCode PetscSFSetErrorOnUnsupportedOverlap(PetscSF sf, MPI_Datatype unit, const void *rootdata, const void *leafdata)
{
  PetscSFLink    link, *p;
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;
  PetscBool      match;

  PetscFunctionBegin;
  if (PetscDefined(USE_DEBUG)) {
    /* Look up links in use and error out if there is a match. When both rootdata and leafdata are NULL, ignore
       the potential overlapping since this process does not participate in communication. Overlapping is harmless.
    */
    if (rootdata || leafdata) {
      for (p = &bas->inuse; (link = *p); p = &link->next) {
        PetscCall(MPIPetsc_Type_compare(unit, link->unit, &match));
        PetscCheck(!match || rootdata != link->rootdata || leafdata != link->leafdata, PETSC_COMM_SELF, PETSC_ERR_SUP, "Overlapped PetscSF with the same rootdata(%p), leafdata(%p) and data type. Undo the overlapping to avoid the error.", rootdata, leafdata);
      }
    }
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode PetscSFLinkMemcpy_Host(PetscSFLink link, PetscMemType dstmtype, void *dst, PetscMemType srcmtype, const void *src, size_t n)
{
  PetscFunctionBegin;
  if (n) PetscCall(PetscMemcpy(dst, src, n));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkSetUp_Host(PetscSF sf, PetscSFLink link, MPI_Datatype unit)
{
  PetscInt    nSignedChar = 0, nUnsignedChar = 0, nInt = 0, nPetscInt = 0, nPetscReal = 0;
  PetscBool   is2Int, is2PetscInt;
  PetscMPIInt ni, na, nd, combiner;
#if defined(PETSC_HAVE_COMPLEX)
  PetscInt nPetscComplex = 0;
#endif

  PetscFunctionBegin;
  PetscCall(MPIPetsc_Type_compare_contig(unit, MPI_SIGNED_CHAR, &nSignedChar));
  PetscCall(MPIPetsc_Type_compare_contig(unit, MPI_UNSIGNED_CHAR, &nUnsignedChar));
  /* MPI_CHAR is treated below as a dumb type that does not support reduction according to MPI standard */
  PetscCall(MPIPetsc_Type_compare_contig(unit, MPI_INT, &nInt));
  PetscCall(MPIPetsc_Type_compare_contig(unit, MPIU_INT, &nPetscInt));
  PetscCall(MPIPetsc_Type_compare_contig(unit, MPIU_REAL, &nPetscReal));
#if defined(PETSC_HAVE_COMPLEX)
  PetscCall(MPIPetsc_Type_compare_contig(unit, MPIU_COMPLEX, &nPetscComplex));
#endif
  PetscCall(MPIPetsc_Type_compare(unit, MPI_2INT, &is2Int));
  PetscCall(MPIPetsc_Type_compare(unit, MPIU_2INT, &is2PetscInt));
  /* TODO: should we also handle Fortran MPI_2REAL? */
  PetscCallMPI(MPI_Type_get_envelope(unit, &ni, &na, &nd, &combiner));
  link->isbuiltin = (combiner == MPI_COMBINER_NAMED) ? PETSC_TRUE : PETSC_FALSE; /* unit is MPI builtin */
  link->bs        = 1;                                                           /* default */

  if (is2Int) {
    PackInit_PairType_int_int_1_1(link);
    link->bs        = 1;
    link->unitbytes = 2 * sizeof(int);
    link->isbuiltin = PETSC_TRUE; /* unit is PETSc builtin */
    link->basicunit = MPI_2INT;
    link->unit      = MPI_2INT;
  } else if (is2PetscInt) { /* TODO: when is2PetscInt and nPetscInt=2, we don't know which path to take. The two paths support different ops. */
    PackInit_PairType_PetscInt_PetscInt_1_1(link);
    link->bs        = 1;
    link->unitbytes = 2 * sizeof(PetscInt);
    link->basicunit = MPIU_2INT;
    link->isbuiltin = PETSC_TRUE; /* unit is PETSc builtin */
    link->unit      = MPIU_2INT;
  } else if (nPetscReal) {
    if (nPetscReal == 8) PackInit_RealType_PetscReal_8_1(link);
    else if (nPetscReal % 8 == 0) PackInit_RealType_PetscReal_8_0(link);
    else if (nPetscReal == 4) PackInit_RealType_PetscReal_4_1(link);
    else if (nPetscReal % 4 == 0) PackInit_RealType_PetscReal_4_0(link);
    else if (nPetscReal == 2) PackInit_RealType_PetscReal_2_1(link);
    else if (nPetscReal % 2 == 0) PackInit_RealType_PetscReal_2_0(link);
    else if (nPetscReal == 1) PackInit_RealType_PetscReal_1_1(link);
    else if (nPetscReal % 1 == 0) PackInit_RealType_PetscReal_1_0(link);
    link->bs        = nPetscReal;
    link->unitbytes = nPetscReal * sizeof(PetscReal);
    link->basicunit = MPIU_REAL;
    if (link->bs == 1) {
      link->isbuiltin = PETSC_TRUE;
      link->unit      = MPIU_REAL;
    }
  } else if (nPetscInt) {
    if (nPetscInt == 8) PackInit_IntegerType_PetscInt_8_1(link);
    else if (nPetscInt % 8 == 0) PackInit_IntegerType_PetscInt_8_0(link);
    else if (nPetscInt == 4) PackInit_IntegerType_PetscInt_4_1(link);
    else if (nPetscInt % 4 == 0) PackInit_IntegerType_PetscInt_4_0(link);
    else if (nPetscInt == 2) PackInit_IntegerType_PetscInt_2_1(link);
    else if (nPetscInt % 2 == 0) PackInit_IntegerType_PetscInt_2_0(link);
    else if (nPetscInt == 1) PackInit_IntegerType_PetscInt_1_1(link);
    else if (nPetscInt % 1 == 0) PackInit_IntegerType_PetscInt_1_0(link);
    link->bs        = nPetscInt;
    link->unitbytes = nPetscInt * sizeof(PetscInt);
    link->basicunit = MPIU_INT;
    if (link->bs == 1) {
      link->isbuiltin = PETSC_TRUE;
      link->unit      = MPIU_INT;
    }
#if defined(PETSC_USE_64BIT_INDICES)
  } else if (nInt) {
    if (nInt == 8) PackInit_IntegerType_int_8_1(link);
    else if (nInt % 8 == 0) PackInit_IntegerType_int_8_0(link);
    else if (nInt == 4) PackInit_IntegerType_int_4_1(link);
    else if (nInt % 4 == 0) PackInit_IntegerType_int_4_0(link);
    else if (nInt == 2) PackInit_IntegerType_int_2_1(link);
    else if (nInt % 2 == 0) PackInit_IntegerType_int_2_0(link);
    else if (nInt == 1) PackInit_IntegerType_int_1_1(link);
    else if (nInt % 1 == 0) PackInit_IntegerType_int_1_0(link);
    link->bs        = nInt;
    link->unitbytes = nInt * sizeof(int);
    link->basicunit = MPI_INT;
    if (link->bs == 1) {
      link->isbuiltin = PETSC_TRUE;
      link->unit      = MPI_INT;
    }
#endif
  } else if (nSignedChar) {
    if (nSignedChar == 8) PackInit_IntegerType_SignedChar_8_1(link);
    else if (nSignedChar % 8 == 0) PackInit_IntegerType_SignedChar_8_0(link);
    else if (nSignedChar == 4) PackInit_IntegerType_SignedChar_4_1(link);
    else if (nSignedChar % 4 == 0) PackInit_IntegerType_SignedChar_4_0(link);
    else if (nSignedChar == 2) PackInit_IntegerType_SignedChar_2_1(link);
    else if (nSignedChar % 2 == 0) PackInit_IntegerType_SignedChar_2_0(link);
    else if (nSignedChar == 1) PackInit_IntegerType_SignedChar_1_1(link);
    else if (nSignedChar % 1 == 0) PackInit_IntegerType_SignedChar_1_0(link);
    link->bs        = nSignedChar;
    link->unitbytes = nSignedChar * sizeof(SignedChar);
    link->basicunit = MPI_SIGNED_CHAR;
    if (link->bs == 1) {
      link->isbuiltin = PETSC_TRUE;
      link->unit      = MPI_SIGNED_CHAR;
    }
  } else if (nUnsignedChar) {
    if (nUnsignedChar == 8) PackInit_IntegerType_UnsignedChar_8_1(link);
    else if (nUnsignedChar % 8 == 0) PackInit_IntegerType_UnsignedChar_8_0(link);
    else if (nUnsignedChar == 4) PackInit_IntegerType_UnsignedChar_4_1(link);
    else if (nUnsignedChar % 4 == 0) PackInit_IntegerType_UnsignedChar_4_0(link);
    else if (nUnsignedChar == 2) PackInit_IntegerType_UnsignedChar_2_1(link);
    else if (nUnsignedChar % 2 == 0) PackInit_IntegerType_UnsignedChar_2_0(link);
    else if (nUnsignedChar == 1) PackInit_IntegerType_UnsignedChar_1_1(link);
    else if (nUnsignedChar % 1 == 0) PackInit_IntegerType_UnsignedChar_1_0(link);
    link->bs        = nUnsignedChar;
    link->unitbytes = nUnsignedChar * sizeof(UnsignedChar);
    link->basicunit = MPI_UNSIGNED_CHAR;
    if (link->bs == 1) {
      link->isbuiltin = PETSC_TRUE;
      link->unit      = MPI_UNSIGNED_CHAR;
    }
#if defined(PETSC_HAVE_COMPLEX)
  } else if (nPetscComplex) {
    if (nPetscComplex == 8) PackInit_ComplexType_PetscComplex_8_1(link);
    else if (nPetscComplex % 8 == 0) PackInit_ComplexType_PetscComplex_8_0(link);
    else if (nPetscComplex == 4) PackInit_ComplexType_PetscComplex_4_1(link);
    else if (nPetscComplex % 4 == 0) PackInit_ComplexType_PetscComplex_4_0(link);
    else if (nPetscComplex == 2) PackInit_ComplexType_PetscComplex_2_1(link);
    else if (nPetscComplex % 2 == 0) PackInit_ComplexType_PetscComplex_2_0(link);
    else if (nPetscComplex == 1) PackInit_ComplexType_PetscComplex_1_1(link);
    else if (nPetscComplex % 1 == 0) PackInit_ComplexType_PetscComplex_1_0(link);
    link->bs        = nPetscComplex;
    link->unitbytes = nPetscComplex * sizeof(PetscComplex);
    link->basicunit = MPIU_COMPLEX;
    if (link->bs == 1) {
      link->isbuiltin = PETSC_TRUE;
      link->unit      = MPIU_COMPLEX;
    }
#endif
  } else {
    MPI_Aint lb, nbyte;
    PetscCallMPI(MPI_Type_get_extent(unit, &lb, &nbyte));
    PetscCheck(lb == 0, PETSC_COMM_SELF, PETSC_ERR_SUP, "Datatype with nonzero lower bound %ld", (long)lb);
    if (nbyte % sizeof(int)) { /* If the type size is not multiple of int */
      if (nbyte == 4) PackInit_DumbType_char_4_1(link);
      else if (nbyte % 4 == 0) PackInit_DumbType_char_4_0(link);
      else if (nbyte == 2) PackInit_DumbType_char_2_1(link);
      else if (nbyte % 2 == 0) PackInit_DumbType_char_2_0(link);
      else if (nbyte == 1) PackInit_DumbType_char_1_1(link);
      else if (nbyte % 1 == 0) PackInit_DumbType_char_1_0(link);
      link->bs        = nbyte;
      link->unitbytes = nbyte;
      link->basicunit = MPI_BYTE;
    } else {
      nInt = nbyte / sizeof(int);
      if (nInt == 8) PackInit_DumbType_DumbInt_8_1(link);
      else if (nInt % 8 == 0) PackInit_DumbType_DumbInt_8_0(link);
      else if (nInt == 4) PackInit_DumbType_DumbInt_4_1(link);
      else if (nInt % 4 == 0) PackInit_DumbType_DumbInt_4_0(link);
      else if (nInt == 2) PackInit_DumbType_DumbInt_2_1(link);
      else if (nInt % 2 == 0) PackInit_DumbType_DumbInt_2_0(link);
      else if (nInt == 1) PackInit_DumbType_DumbInt_1_1(link);
      else if (nInt % 1 == 0) PackInit_DumbType_DumbInt_1_0(link);
      link->bs        = nInt;
      link->unitbytes = nbyte;
      link->basicunit = MPI_INT;
    }
    if (link->isbuiltin) link->unit = unit;
  }

  if (!link->isbuiltin) PetscCallMPI(MPI_Type_dup(unit, &link->unit));

  link->Memcpy = PetscSFLinkMemcpy_Host;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkGetUnpackAndOp(PetscSFLink link, PetscMemType mtype, MPI_Op op, PetscBool atomic, PetscErrorCode (**UnpackAndOp)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, void *, const void *))
{
  PetscFunctionBegin;
  *UnpackAndOp = NULL;
  if (PetscMemTypeHost(mtype)) {
    if (op == MPI_REPLACE) *UnpackAndOp = link->h_UnpackAndInsert;
    else if (op == MPI_SUM || op == MPIU_SUM) *UnpackAndOp = link->h_UnpackAndAdd;
    else if (op == MPI_PROD) *UnpackAndOp = link->h_UnpackAndMult;
    else if (op == MPI_MAX || op == MPIU_MAX) *UnpackAndOp = link->h_UnpackAndMax;
    else if (op == MPI_MIN || op == MPIU_MIN) *UnpackAndOp = link->h_UnpackAndMin;
    else if (op == MPI_LAND) *UnpackAndOp = link->h_UnpackAndLAND;
    else if (op == MPI_BAND) *UnpackAndOp = link->h_UnpackAndBAND;
    else if (op == MPI_LOR) *UnpackAndOp = link->h_UnpackAndLOR;
    else if (op == MPI_BOR) *UnpackAndOp = link->h_UnpackAndBOR;
    else if (op == MPI_LXOR) *UnpackAndOp = link->h_UnpackAndLXOR;
    else if (op == MPI_BXOR) *UnpackAndOp = link->h_UnpackAndBXOR;
    else if (op == MPI_MAXLOC) *UnpackAndOp = link->h_UnpackAndMaxloc;
    else if (op == MPI_MINLOC) *UnpackAndOp = link->h_UnpackAndMinloc;
  }
#if defined(PETSC_HAVE_DEVICE)
  else if (PetscMemTypeDevice(mtype) && !atomic) {
    if (op == MPI_REPLACE) *UnpackAndOp = link->d_UnpackAndInsert;
    else if (op == MPI_SUM || op == MPIU_SUM) *UnpackAndOp = link->d_UnpackAndAdd;
    else if (op == MPI_PROD) *UnpackAndOp = link->d_UnpackAndMult;
    else if (op == MPI_MAX || op == MPIU_MAX) *UnpackAndOp = link->d_UnpackAndMax;
    else if (op == MPI_MIN || op == MPIU_MIN) *UnpackAndOp = link->d_UnpackAndMin;
    else if (op == MPI_LAND) *UnpackAndOp = link->d_UnpackAndLAND;
    else if (op == MPI_BAND) *UnpackAndOp = link->d_UnpackAndBAND;
    else if (op == MPI_LOR) *UnpackAndOp = link->d_UnpackAndLOR;
    else if (op == MPI_BOR) *UnpackAndOp = link->d_UnpackAndBOR;
    else if (op == MPI_LXOR) *UnpackAndOp = link->d_UnpackAndLXOR;
    else if (op == MPI_BXOR) *UnpackAndOp = link->d_UnpackAndBXOR;
    else if (op == MPI_MAXLOC) *UnpackAndOp = link->d_UnpackAndMaxloc;
    else if (op == MPI_MINLOC) *UnpackAndOp = link->d_UnpackAndMinloc;
  } else if (PetscMemTypeDevice(mtype) && atomic) {
    if (op == MPI_REPLACE) *UnpackAndOp = link->da_UnpackAndInsert;
    else if (op == MPI_SUM || op == MPIU_SUM) *UnpackAndOp = link->da_UnpackAndAdd;
    else if (op == MPI_PROD) *UnpackAndOp = link->da_UnpackAndMult;
    else if (op == MPI_MAX || op == MPIU_MAX) *UnpackAndOp = link->da_UnpackAndMax;
    else if (op == MPI_MIN || op == MPIU_MIN) *UnpackAndOp = link->da_UnpackAndMin;
    else if (op == MPI_LAND) *UnpackAndOp = link->da_UnpackAndLAND;
    else if (op == MPI_BAND) *UnpackAndOp = link->da_UnpackAndBAND;
    else if (op == MPI_LOR) *UnpackAndOp = link->da_UnpackAndLOR;
    else if (op == MPI_BOR) *UnpackAndOp = link->da_UnpackAndBOR;
    else if (op == MPI_LXOR) *UnpackAndOp = link->da_UnpackAndLXOR;
    else if (op == MPI_BXOR) *UnpackAndOp = link->da_UnpackAndBXOR;
    else if (op == MPI_MAXLOC) *UnpackAndOp = link->da_UnpackAndMaxloc;
    else if (op == MPI_MINLOC) *UnpackAndOp = link->da_UnpackAndMinloc;
  }
#endif
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkGetScatterAndOp(PetscSFLink link, PetscMemType mtype, MPI_Op op, PetscBool atomic, PetscErrorCode (**ScatterAndOp)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, const void *, PetscInt, PetscSFPackOpt, const PetscInt *, void *))
{
  PetscFunctionBegin;
  *ScatterAndOp = NULL;
  if (PetscMemTypeHost(mtype)) {
    if (op == MPI_REPLACE) *ScatterAndOp = link->h_ScatterAndInsert;
    else if (op == MPI_SUM || op == MPIU_SUM) *ScatterAndOp = link->h_ScatterAndAdd;
    else if (op == MPI_PROD) *ScatterAndOp = link->h_ScatterAndMult;
    else if (op == MPI_MAX || op == MPIU_MAX) *ScatterAndOp = link->h_ScatterAndMax;
    else if (op == MPI_MIN || op == MPIU_MIN) *ScatterAndOp = link->h_ScatterAndMin;
    else if (op == MPI_LAND) *ScatterAndOp = link->h_ScatterAndLAND;
    else if (op == MPI_BAND) *ScatterAndOp = link->h_ScatterAndBAND;
    else if (op == MPI_LOR) *ScatterAndOp = link->h_ScatterAndLOR;
    else if (op == MPI_BOR) *ScatterAndOp = link->h_ScatterAndBOR;
    else if (op == MPI_LXOR) *ScatterAndOp = link->h_ScatterAndLXOR;
    else if (op == MPI_BXOR) *ScatterAndOp = link->h_ScatterAndBXOR;
    else if (op == MPI_MAXLOC) *ScatterAndOp = link->h_ScatterAndMaxloc;
    else if (op == MPI_MINLOC) *ScatterAndOp = link->h_ScatterAndMinloc;
  }
#if defined(PETSC_HAVE_DEVICE)
  else if (PetscMemTypeDevice(mtype) && !atomic) {
    if (op == MPI_REPLACE) *ScatterAndOp = link->d_ScatterAndInsert;
    else if (op == MPI_SUM || op == MPIU_SUM) *ScatterAndOp = link->d_ScatterAndAdd;
    else if (op == MPI_PROD) *ScatterAndOp = link->d_ScatterAndMult;
    else if (op == MPI_MAX || op == MPIU_MAX) *ScatterAndOp = link->d_ScatterAndMax;
    else if (op == MPI_MIN || op == MPIU_MIN) *ScatterAndOp = link->d_ScatterAndMin;
    else if (op == MPI_LAND) *ScatterAndOp = link->d_ScatterAndLAND;
    else if (op == MPI_BAND) *ScatterAndOp = link->d_ScatterAndBAND;
    else if (op == MPI_LOR) *ScatterAndOp = link->d_ScatterAndLOR;
    else if (op == MPI_BOR) *ScatterAndOp = link->d_ScatterAndBOR;
    else if (op == MPI_LXOR) *ScatterAndOp = link->d_ScatterAndLXOR;
    else if (op == MPI_BXOR) *ScatterAndOp = link->d_ScatterAndBXOR;
    else if (op == MPI_MAXLOC) *ScatterAndOp = link->d_ScatterAndMaxloc;
    else if (op == MPI_MINLOC) *ScatterAndOp = link->d_ScatterAndMinloc;
  } else if (PetscMemTypeDevice(mtype) && atomic) {
    if (op == MPI_REPLACE) *ScatterAndOp = link->da_ScatterAndInsert;
    else if (op == MPI_SUM || op == MPIU_SUM) *ScatterAndOp = link->da_ScatterAndAdd;
    else if (op == MPI_PROD) *ScatterAndOp = link->da_ScatterAndMult;
    else if (op == MPI_MAX || op == MPIU_MAX) *ScatterAndOp = link->da_ScatterAndMax;
    else if (op == MPI_MIN || op == MPIU_MIN) *ScatterAndOp = link->da_ScatterAndMin;
    else if (op == MPI_LAND) *ScatterAndOp = link->da_ScatterAndLAND;
    else if (op == MPI_BAND) *ScatterAndOp = link->da_ScatterAndBAND;
    else if (op == MPI_LOR) *ScatterAndOp = link->da_ScatterAndLOR;
    else if (op == MPI_BOR) *ScatterAndOp = link->da_ScatterAndBOR;
    else if (op == MPI_LXOR) *ScatterAndOp = link->da_ScatterAndLXOR;
    else if (op == MPI_BXOR) *ScatterAndOp = link->da_ScatterAndBXOR;
    else if (op == MPI_MAXLOC) *ScatterAndOp = link->da_ScatterAndMaxloc;
    else if (op == MPI_MINLOC) *ScatterAndOp = link->da_ScatterAndMinloc;
  }
#endif
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkGetFetchAndOp(PetscSFLink link, PetscMemType mtype, MPI_Op op, PetscBool atomic, PetscErrorCode (**FetchAndOp)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, void *, void *))
{
  PetscFunctionBegin;
  *FetchAndOp = NULL;
  PetscCheck(op == MPI_SUM || op == MPIU_SUM, PETSC_COMM_SELF, PETSC_ERR_SUP, "No support for MPI_Op in FetchAndOp");
  if (PetscMemTypeHost(mtype)) *FetchAndOp = link->h_FetchAndAdd;
#if defined(PETSC_HAVE_DEVICE)
  else if (PetscMemTypeDevice(mtype) && !atomic) *FetchAndOp = link->d_FetchAndAdd;
  else if (PetscMemTypeDevice(mtype) && atomic) *FetchAndOp = link->da_FetchAndAdd;
#endif
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkGetFetchAndOpLocal(PetscSFLink link, PetscMemType mtype, MPI_Op op, PetscBool atomic, PetscErrorCode (**FetchAndOpLocal)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, void *, PetscInt, PetscSFPackOpt, const PetscInt *, const void *, void *))
{
  PetscFunctionBegin;
  *FetchAndOpLocal = NULL;
  PetscCheck(op == MPI_SUM || op == MPIU_SUM, PETSC_COMM_SELF, PETSC_ERR_SUP, "No support for MPI_Op in FetchAndOp");
  if (PetscMemTypeHost(mtype)) *FetchAndOpLocal = link->h_FetchAndAddLocal;
#if defined(PETSC_HAVE_DEVICE)
  else if (PetscMemTypeDevice(mtype) && !atomic) *FetchAndOpLocal = link->d_FetchAndAddLocal;
  else if (PetscMemTypeDevice(mtype) && atomic) *FetchAndOpLocal = link->da_FetchAndAddLocal;
#endif
  PetscFunctionReturn(PETSC_SUCCESS);
}

static inline PetscErrorCode PetscSFLinkLogFlopsAfterUnpackRootData(PetscSF sf, PetscSFLink link, PetscSFScope scope, MPI_Op op)
{
  PetscLogDouble flops;
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;

  PetscFunctionBegin;
  if (op != MPI_REPLACE && link->basicunit == MPIU_SCALAR) { /* op is a reduction on PetscScalars */
    flops = bas->rootbuflen[scope] * link->bs;               /* # of roots in buffer x # of scalars in unit */
#if defined(PETSC_HAVE_DEVICE)
    if (PetscMemTypeDevice(link->rootmtype)) PetscCall(PetscLogGpuFlops(flops));
    else
#endif
      PetscCall(PetscLogFlops(flops));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static inline PetscErrorCode PetscSFLinkLogFlopsAfterUnpackLeafData(PetscSF sf, PetscSFLink link, PetscSFScope scope, MPI_Op op)
{
  PetscLogDouble flops;

  PetscFunctionBegin;
  if (op != MPI_REPLACE && link->basicunit == MPIU_SCALAR) { /* op is a reduction on PetscScalars */
    flops = sf->leafbuflen[scope] * link->bs;                /* # of roots in buffer x # of scalars in unit */
#if defined(PETSC_HAVE_DEVICE)
    if (PetscMemTypeDevice(link->leafmtype)) PetscCall(PetscLogGpuFlops(flops));
    else
#endif
      PetscCall(PetscLogFlops(flops));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/* When SF could not find a proper UnpackAndOp() from link, it falls back to MPI_Reduce_local.
  Input Parameters:
  +sf      - The StarForest
  .link    - The link
  .count   - Number of entries to unpack
  .start   - The first index, significant when indices=NULL
  .indices - Indices of entries in <data>. If NULL, it means indices are contiguous and the first is given in <start>
  .buf     - A contiguous buffer to unpack from
  -op      - Operation after unpack

  Output Parameters:
  .data    - The data to unpack to
*/
static inline PetscErrorCode PetscSFLinkUnpackDataWithMPIReduceLocal(PetscSF sf, PetscSFLink link, PetscInt count, PetscInt start, const PetscInt *indices, void *data, const void *buf, MPI_Op op)
{
  PetscFunctionBegin;
#if defined(PETSC_HAVE_MPI_REDUCE_LOCAL)
  {
    PetscInt i;
    if (indices) {
      /* Note we use link->unit instead of link->basicunit. When op can be mapped to MPI_SUM etc, it operates on
         basic units of a root/leaf element-wisely. Otherwise, it is meant to operate on a whole root/leaf.
      */
      for (i = 0; i < count; i++) PetscCallMPI(MPI_Reduce_local((const char *)buf + i * link->unitbytes, (char *)data + indices[i] * link->unitbytes, 1, link->unit, op));
    } else {
      PetscCallMPI(MPIU_Reduce_local(buf, (char *)data + start * link->unitbytes, count, link->unit, op));
    }
  }
  PetscFunctionReturn(PETSC_SUCCESS);
#else
  SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "No unpacking reduction operation for this MPI_Op");
#endif
}

static inline PetscErrorCode PetscSFLinkScatterDataWithMPIReduceLocal(PetscSF sf, PetscSFLink link, PetscInt count, PetscInt srcStart, const PetscInt *srcIdx, const void *src, PetscInt dstStart, const PetscInt *dstIdx, void *dst, MPI_Op op)
{
  PetscFunctionBegin;
#if defined(PETSC_HAVE_MPI_REDUCE_LOCAL)
  {
    PetscInt i, disp;
    if (!srcIdx) {
      PetscCall(PetscSFLinkUnpackDataWithMPIReduceLocal(sf, link, count, dstStart, dstIdx, dst, (const char *)src + srcStart * link->unitbytes, op));
    } else {
      for (i = 0; i < count; i++) {
        disp = dstIdx ? dstIdx[i] : dstStart + i;
        PetscCallMPI(MPIU_Reduce_local((const char *)src + srcIdx[i] * link->unitbytes, (char *)dst + disp * link->unitbytes, 1, link->unit, op));
      }
    }
  }
  PetscFunctionReturn(PETSC_SUCCESS);
#else
  SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "No unpacking reduction operation for this MPI_Op");
#endif
}

/*=============================================================================
              Pack/Unpack/Fetch/Scatter routines
 ============================================================================*/

/* Pack rootdata to rootbuf
  Input Parameters:
  + sf       - The SF this packing works on.
  . link     - It gives the memtype of the roots and also provides root buffer.
  . scope    - PETSCSF_LOCAL or PETSCSF_REMOTE. Note SF has the ability to do local and remote communications separately.
  - rootdata - Where to read the roots.

  Notes:
  When rootdata can be directly used as root buffer, the routine is almost a no-op. After the call, root data is
  in a place where the underlying MPI is ready to access (use_gpu_aware_mpi or not)
 */
static PetscErrorCode PetscSFLinkPackRootData_Private(PetscSF sf, PetscSFLink link, PetscSFScope scope, const void *rootdata)
{
  const PetscInt *rootindices = NULL;
  PetscInt        count, start;
  PetscErrorCode (*Pack)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, const void *, void *) = NULL;
  PetscMemType   rootmtype                                                                                        = link->rootmtype;
  PetscSFPackOpt opt                                                                                              = NULL;

  PetscFunctionBegin;
  if (!link->rootdirect[scope]) { /* If rootdata works directly as rootbuf, skip packing */
    PetscCall(PetscSFLinkGetRootPackOptAndIndices(sf, link, rootmtype, scope, &count, &start, &opt, &rootindices));
    PetscCall(PetscSFLinkGetPack(link, rootmtype, &Pack));
    PetscCall((*Pack)(link, count, start, opt, rootindices, rootdata, link->rootbuf[scope][rootmtype]));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/* Pack leafdata to leafbuf */
static PetscErrorCode PetscSFLinkPackLeafData_Private(PetscSF sf, PetscSFLink link, PetscSFScope scope, const void *leafdata)
{
  const PetscInt *leafindices = NULL;
  PetscInt        count, start;
  PetscErrorCode (*Pack)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, const void *, void *) = NULL;
  PetscMemType   leafmtype                                                                                        = link->leafmtype;
  PetscSFPackOpt opt                                                                                              = NULL;

  PetscFunctionBegin;
  if (!link->leafdirect[scope]) { /* If leafdata works directly as rootbuf, skip packing */
    PetscCall(PetscSFLinkGetLeafPackOptAndIndices(sf, link, leafmtype, scope, &count, &start, &opt, &leafindices));
    PetscCall(PetscSFLinkGetPack(link, leafmtype, &Pack));
    PetscCall((*Pack)(link, count, start, opt, leafindices, leafdata, link->leafbuf[scope][leafmtype]));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/* Pack rootdata to rootbuf, which are in the same memory space */
PetscErrorCode PetscSFLinkPackRootData(PetscSF sf, PetscSFLink link, PetscSFScope scope, const void *rootdata)
{
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;

  PetscFunctionBegin;
  if (scope == PETSCSF_REMOTE) { /* Sync the device if rootdata is not on petsc default stream */
    if (PetscMemTypeDevice(link->rootmtype) && link->SyncDevice && sf->unknown_input_stream) PetscCall((*link->SyncDevice)(link));
    if (link->PrePack) PetscCall((*link->PrePack)(sf, link, PETSCSF_ROOT2LEAF)); /* Used by SF nvshmem */
  }
  PetscCall(PetscLogEventBegin(PETSCSF_Pack, sf, 0, 0, 0));
  if (bas->rootbuflen[scope]) PetscCall(PetscSFLinkPackRootData_Private(sf, link, scope, rootdata));
  PetscCall(PetscLogEventEnd(PETSCSF_Pack, sf, 0, 0, 0));
  PetscFunctionReturn(PETSC_SUCCESS);
}
/* Pack leafdata to leafbuf, which are in the same memory space */
PetscErrorCode PetscSFLinkPackLeafData(PetscSF sf, PetscSFLink link, PetscSFScope scope, const void *leafdata)
{
  PetscFunctionBegin;
  if (scope == PETSCSF_REMOTE) {
    if (PetscMemTypeDevice(link->leafmtype) && link->SyncDevice && sf->unknown_input_stream) PetscCall((*link->SyncDevice)(link));
    if (link->PrePack) PetscCall((*link->PrePack)(sf, link, PETSCSF_LEAF2ROOT)); /* Used by SF nvshmem */
  }
  PetscCall(PetscLogEventBegin(PETSCSF_Pack, sf, 0, 0, 0));
  if (sf->leafbuflen[scope]) PetscCall(PetscSFLinkPackLeafData_Private(sf, link, scope, leafdata));
  PetscCall(PetscLogEventEnd(PETSCSF_Pack, sf, 0, 0, 0));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode PetscSFLinkUnpackRootData_Private(PetscSF sf, PetscSFLink link, PetscSFScope scope, void *rootdata, MPI_Op op)
{
  const PetscInt *rootindices = NULL;
  PetscInt        count, start;
  PetscSF_Basic  *bas                                                                                                    = (PetscSF_Basic *)sf->data;
  PetscErrorCode (*UnpackAndOp)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, void *, const void *) = NULL;
  PetscMemType   rootmtype                                                                                               = link->rootmtype;
  PetscSFPackOpt opt                                                                                                     = NULL;

  PetscFunctionBegin;
  if (!link->rootdirect[scope]) { /* If rootdata works directly as rootbuf, skip unpacking */
    PetscCall(PetscSFLinkGetUnpackAndOp(link, rootmtype, op, bas->rootdups[scope], &UnpackAndOp));
    if (UnpackAndOp) {
      PetscCall(PetscSFLinkGetRootPackOptAndIndices(sf, link, rootmtype, scope, &count, &start, &opt, &rootindices));
      PetscCall((*UnpackAndOp)(link, count, start, opt, rootindices, rootdata, link->rootbuf[scope][rootmtype]));
    } else {
      PetscCall(PetscSFLinkGetRootPackOptAndIndices(sf, link, PETSC_MEMTYPE_HOST, scope, &count, &start, &opt, &rootindices));
      PetscCall(PetscSFLinkUnpackDataWithMPIReduceLocal(sf, link, count, start, rootindices, rootdata, link->rootbuf[scope][rootmtype], op));
    }
  }
  PetscCall(PetscSFLinkLogFlopsAfterUnpackRootData(sf, link, scope, op));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode PetscSFLinkUnpackLeafData_Private(PetscSF sf, PetscSFLink link, PetscSFScope scope, void *leafdata, MPI_Op op)
{
  const PetscInt *leafindices = NULL;
  PetscInt        count, start;
  PetscErrorCode (*UnpackAndOp)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, void *, const void *) = NULL;
  PetscMemType   leafmtype                                                                                               = link->leafmtype;
  PetscSFPackOpt opt                                                                                                     = NULL;

  PetscFunctionBegin;
  if (!link->leafdirect[scope]) { /* If leafdata works directly as rootbuf, skip unpacking */
    PetscCall(PetscSFLinkGetUnpackAndOp(link, leafmtype, op, sf->leafdups[scope], &UnpackAndOp));
    if (UnpackAndOp) {
      PetscCall(PetscSFLinkGetLeafPackOptAndIndices(sf, link, leafmtype, scope, &count, &start, &opt, &leafindices));
      PetscCall((*UnpackAndOp)(link, count, start, opt, leafindices, leafdata, link->leafbuf[scope][leafmtype]));
    } else {
      PetscCall(PetscSFLinkGetLeafPackOptAndIndices(sf, link, PETSC_MEMTYPE_HOST, scope, &count, &start, &opt, &leafindices));
      PetscCall(PetscSFLinkUnpackDataWithMPIReduceLocal(sf, link, count, start, leafindices, leafdata, link->leafbuf[scope][leafmtype], op));
    }
  }
  PetscCall(PetscSFLinkLogFlopsAfterUnpackLeafData(sf, link, scope, op));
  PetscFunctionReturn(PETSC_SUCCESS);
}
/* Unpack rootbuf to rootdata, which are in the same memory space */
PetscErrorCode PetscSFLinkUnpackRootData(PetscSF sf, PetscSFLink link, PetscSFScope scope, void *rootdata, MPI_Op op)
{
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;

  PetscFunctionBegin;
  PetscCall(PetscLogEventBegin(PETSCSF_Unpack, sf, 0, 0, 0));
  if (bas->rootbuflen[scope]) PetscCall(PetscSFLinkUnpackRootData_Private(sf, link, scope, rootdata, op));
  PetscCall(PetscLogEventEnd(PETSCSF_Unpack, sf, 0, 0, 0));
  if (scope == PETSCSF_REMOTE) {
    if (link->PostUnpack) PetscCall((*link->PostUnpack)(sf, link, PETSCSF_LEAF2ROOT)); /* Used by SF nvshmem */
    if (PetscMemTypeDevice(link->rootmtype) && link->SyncDevice && sf->unknown_input_stream) PetscCall((*link->SyncDevice)(link));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/* Unpack leafbuf to leafdata for remote (common case) or local (rare case when rootmtype != leafmtype) */
PetscErrorCode PetscSFLinkUnpackLeafData(PetscSF sf, PetscSFLink link, PetscSFScope scope, void *leafdata, MPI_Op op)
{
  PetscFunctionBegin;
  PetscCall(PetscLogEventBegin(PETSCSF_Unpack, sf, 0, 0, 0));
  if (sf->leafbuflen[scope]) PetscCall(PetscSFLinkUnpackLeafData_Private(sf, link, scope, leafdata, op));
  PetscCall(PetscLogEventEnd(PETSCSF_Unpack, sf, 0, 0, 0));
  if (scope == PETSCSF_REMOTE) {
    if (link->PostUnpack) PetscCall((*link->PostUnpack)(sf, link, PETSCSF_ROOT2LEAF)); /* Used by SF nvshmem */
    if (PetscMemTypeDevice(link->leafmtype) && link->SyncDevice && sf->unknown_input_stream) PetscCall((*link->SyncDevice)(link));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/* FetchAndOp rootdata with rootbuf, it is a kind of Unpack on rootdata, except it also updates rootbuf */
PetscErrorCode PetscSFLinkFetchAndOpRemote(PetscSF sf, PetscSFLink link, void *rootdata, MPI_Op op)
{
  const PetscInt *rootindices = NULL;
  PetscInt        count, start;
  PetscSF_Basic  *bas                                                                                             = (PetscSF_Basic *)sf->data;
  PetscErrorCode (*FetchAndOp)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, void *, void *) = NULL;
  PetscMemType   rootmtype                                                                                        = link->rootmtype;
  PetscSFPackOpt opt                                                                                              = NULL;

  PetscFunctionBegin;
  PetscCall(PetscLogEventBegin(PETSCSF_Unpack, sf, 0, 0, 0));
  if (bas->rootbuflen[PETSCSF_REMOTE]) {
    /* Do FetchAndOp on rootdata with rootbuf */
    PetscCall(PetscSFLinkGetFetchAndOp(link, rootmtype, op, bas->rootdups[PETSCSF_REMOTE], &FetchAndOp));
    PetscCall(PetscSFLinkGetRootPackOptAndIndices(sf, link, rootmtype, PETSCSF_REMOTE, &count, &start, &opt, &rootindices));
    PetscCall((*FetchAndOp)(link, count, start, opt, rootindices, rootdata, link->rootbuf[PETSCSF_REMOTE][rootmtype]));
  }
  PetscCall(PetscSFLinkLogFlopsAfterUnpackRootData(sf, link, PETSCSF_REMOTE, op));
  PetscCall(PetscLogEventEnd(PETSCSF_Unpack, sf, 0, 0, 0));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFLinkScatterLocal(PetscSF sf, PetscSFLink link, PetscSFDirection direction, void *rootdata, void *leafdata, MPI_Op op)
{
  const PetscInt *rootindices = NULL, *leafindices = NULL;
  PetscInt        count, rootstart, leafstart;
  PetscSF_Basic  *bas                                                                                                                                                 = (PetscSF_Basic *)sf->data;
  PetscErrorCode (*ScatterAndOp)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, const void *, PetscInt, PetscSFPackOpt, const PetscInt *, void *) = NULL;
  PetscMemType   rootmtype = link->rootmtype, leafmtype = link->leafmtype, srcmtype, dstmtype;
  PetscSFPackOpt leafopt = NULL, rootopt = NULL;
  PetscInt       buflen = sf->leafbuflen[PETSCSF_LOCAL];
  char          *srcbuf = NULL, *dstbuf = NULL;
  PetscBool      dstdups;

  PetscFunctionBegin;
  if (!buflen) PetscFunctionReturn(PETSC_SUCCESS);
  if (rootmtype != leafmtype) { /* The cross memory space local scatter is done by pack, copy and unpack */
    if (direction == PETSCSF_ROOT2LEAF) {
      PetscCall(PetscSFLinkPackRootData(sf, link, PETSCSF_LOCAL, rootdata));
      srcmtype = rootmtype;
      srcbuf   = link->rootbuf[PETSCSF_LOCAL][rootmtype];
      dstmtype = leafmtype;
      dstbuf   = link->leafbuf[PETSCSF_LOCAL][leafmtype];
    } else {
      PetscCall(PetscSFLinkPackLeafData(sf, link, PETSCSF_LOCAL, leafdata));
      srcmtype = leafmtype;
      srcbuf   = link->leafbuf[PETSCSF_LOCAL][leafmtype];
      dstmtype = rootmtype;
      dstbuf   = link->rootbuf[PETSCSF_LOCAL][rootmtype];
    }
    PetscCall((*link->Memcpy)(link, dstmtype, dstbuf, srcmtype, srcbuf, buflen * link->unitbytes));
    /* If above is a device to host copy, we have to sync the stream before accessing the buffer on host */
    if (PetscMemTypeHost(dstmtype)) PetscCall((*link->SyncStream)(link));
    if (direction == PETSCSF_ROOT2LEAF) {
      PetscCall(PetscSFLinkUnpackLeafData(sf, link, PETSCSF_LOCAL, leafdata, op));
    } else {
      PetscCall(PetscSFLinkUnpackRootData(sf, link, PETSCSF_LOCAL, rootdata, op));
    }
  } else {
    dstdups  = (direction == PETSCSF_ROOT2LEAF) ? sf->leafdups[PETSCSF_LOCAL] : bas->rootdups[PETSCSF_LOCAL];
    dstmtype = (direction == PETSCSF_ROOT2LEAF) ? link->leafmtype : link->rootmtype;
    PetscCall(PetscSFLinkGetScatterAndOp(link, dstmtype, op, dstdups, &ScatterAndOp));
    if (ScatterAndOp) {
      PetscCall(PetscSFLinkGetRootPackOptAndIndices(sf, link, rootmtype, PETSCSF_LOCAL, &count, &rootstart, &rootopt, &rootindices));
      PetscCall(PetscSFLinkGetLeafPackOptAndIndices(sf, link, leafmtype, PETSCSF_LOCAL, &count, &leafstart, &leafopt, &leafindices));
      if (direction == PETSCSF_ROOT2LEAF) {
        PetscCall((*ScatterAndOp)(link, count, rootstart, rootopt, rootindices, rootdata, leafstart, leafopt, leafindices, leafdata));
      } else {
        PetscCall((*ScatterAndOp)(link, count, leafstart, leafopt, leafindices, leafdata, rootstart, rootopt, rootindices, rootdata));
      }
    } else {
      PetscCall(PetscSFLinkGetRootPackOptAndIndices(sf, link, PETSC_MEMTYPE_HOST, PETSCSF_LOCAL, &count, &rootstart, &rootopt, &rootindices));
      PetscCall(PetscSFLinkGetLeafPackOptAndIndices(sf, link, PETSC_MEMTYPE_HOST, PETSCSF_LOCAL, &count, &leafstart, &leafopt, &leafindices));
      if (direction == PETSCSF_ROOT2LEAF) {
        PetscCall(PetscSFLinkScatterDataWithMPIReduceLocal(sf, link, count, rootstart, rootindices, rootdata, leafstart, leafindices, leafdata, op));
      } else {
        PetscCall(PetscSFLinkScatterDataWithMPIReduceLocal(sf, link, count, leafstart, leafindices, leafdata, rootstart, rootindices, rootdata, op));
      }
    }
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/* Fetch rootdata to leafdata and leafupdate locally */
PetscErrorCode PetscSFLinkFetchAndOpLocal(PetscSF sf, PetscSFLink link, void *rootdata, const void *leafdata, void *leafupdate, MPI_Op op)
{
  const PetscInt *rootindices = NULL, *leafindices = NULL;
  PetscInt        count, rootstart, leafstart;
  PetscSF_Basic  *bas                                                                                                                                                            = (PetscSF_Basic *)sf->data;
  PetscErrorCode (*FetchAndOpLocal)(PetscSFLink, PetscInt, PetscInt, PetscSFPackOpt, const PetscInt *, void *, PetscInt, PetscSFPackOpt, const PetscInt *, const void *, void *) = NULL;
  const PetscMemType rootmtype = link->rootmtype, leafmtype = link->leafmtype;
  PetscSFPackOpt     leafopt = NULL, rootopt = NULL;

  PetscFunctionBegin;
  if (!bas->rootbuflen[PETSCSF_LOCAL]) PetscFunctionReturn(PETSC_SUCCESS);
  if (rootmtype != leafmtype) {
    /* The local communication has to go through pack and unpack */
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Doing PetscSFFetchAndOp with rootdata and leafdata on opposite side of CPU and GPU");
  } else {
    PetscCall(PetscSFLinkGetRootPackOptAndIndices(sf, link, rootmtype, PETSCSF_LOCAL, &count, &rootstart, &rootopt, &rootindices));
    PetscCall(PetscSFLinkGetLeafPackOptAndIndices(sf, link, leafmtype, PETSCSF_LOCAL, &count, &leafstart, &leafopt, &leafindices));
    PetscCall(PetscSFLinkGetFetchAndOpLocal(link, rootmtype, op, bas->rootdups[PETSCSF_LOCAL], &FetchAndOpLocal));
    PetscCall((*FetchAndOpLocal)(link, count, rootstart, rootopt, rootindices, rootdata, leafstart, leafopt, leafindices, leafdata, leafupdate));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*
  Create per-rank pack/unpack optimizations based on indices patterns

   Input Parameters:
  +  n       - Number of destination ranks
  .  offset  - [n+1] For the i-th rank, its associated indices are idx[offset[i], offset[i+1]). offset[0] needs not to be 0.
  -  idx     - [*]   Array storing indices

   Output Parameters:
  +  opt     - Pack optimizations. NULL if no optimizations.
*/
static PetscErrorCode PetscSFCreatePackOpt(PetscInt n, const PetscInt *offset, const PetscInt *idx, PetscSFPackOpt *out)
{
  PetscInt       r, p, start, i, j, k, dx, dy, dz, dydz, m, X, Y;
  PetscBool      optimizable = PETSC_TRUE;
  PetscSFPackOpt opt;

  PetscFunctionBegin;
  PetscCall(PetscMalloc1(1, &opt));
  PetscCall(PetscMalloc1(7 * n + 2, &opt->array));
  opt->n = opt->array[0] = n;
  opt->offset            = opt->array + 1;
  opt->start             = opt->array + n + 2;
  opt->dx                = opt->array + 2 * n + 2;
  opt->dy                = opt->array + 3 * n + 2;
  opt->dz                = opt->array + 4 * n + 2;
  opt->X                 = opt->array + 5 * n + 2;
  opt->Y                 = opt->array + 6 * n + 2;

  for (r = 0; r < n; r++) {            /* For each destination rank */
    m     = offset[r + 1] - offset[r]; /* Total number of indices for this rank. We want to see if m can be factored into dx*dy*dz */
    p     = offset[r];
    start = idx[p]; /* First index for this rank */
    p++;

    /* Search in X dimension */
    for (dx = 1; dx < m; dx++, p++) {
      if (start + dx != idx[p]) break;
    }

    dydz = m / dx;
    X    = dydz > 1 ? (idx[p] - start) : dx;
    /* Not optimizable if m is not a multiple of dx, or some unrecognized pattern is found */
    if (m % dx || X <= 0) {
      optimizable = PETSC_FALSE;
      goto finish;
    }
    for (dy = 1; dy < dydz; dy++) { /* Search in Y dimension */
      for (i = 0; i < dx; i++, p++) {
        if (start + X * dy + i != idx[p]) {
          if (i) {
            optimizable = PETSC_FALSE;
            goto finish;
          } /* The pattern is violated in the middle of an x-walk */
          else
            goto Z_dimension;
        }
      }
    }

  Z_dimension:
    dz = m / (dx * dy);
    Y  = dz > 1 ? (idx[p] - start) / X : dy;
    /* Not optimizable if m is not a multiple of dx*dy, or some unrecognized pattern is found */
    if (m % (dx * dy) || Y <= 0) {
      optimizable = PETSC_FALSE;
      goto finish;
    }
    for (k = 1; k < dz; k++) { /* Go through Z dimension to see if remaining indices follow the pattern */
      for (j = 0; j < dy; j++) {
        for (i = 0; i < dx; i++, p++) {
          if (start + X * Y * k + X * j + i != idx[p]) {
            optimizable = PETSC_FALSE;
            goto finish;
          }
        }
      }
    }
    opt->start[r] = start;
    opt->dx[r]    = dx;
    opt->dy[r]    = dy;
    opt->dz[r]    = dz;
    opt->X[r]     = X;
    opt->Y[r]     = Y;
  }

finish:
  /* If not optimizable, free arrays to save memory */
  if (!n || !optimizable) {
    PetscCall(PetscFree(opt->array));
    PetscCall(PetscFree(opt));
    *out = NULL;
  } else {
    opt->offset[0] = 0;
    for (r = 0; r < n; r++) opt->offset[r + 1] = opt->offset[r] + opt->dx[r] * opt->dy[r] * opt->dz[r];
    *out = opt;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

static inline PetscErrorCode PetscSFDestroyPackOpt(PetscSF sf, PetscMemType mtype, PetscSFPackOpt *out)
{
  PetscSFPackOpt opt = *out;

  PetscFunctionBegin;
  if (opt) {
    PetscCall(PetscSFFree(sf, mtype, opt->array));
    PetscCall(PetscFree(opt));
    *out = NULL;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFSetUpPackFields(PetscSF sf)
{
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;
  PetscInt       i, j;

  PetscFunctionBegin;
  /* [0] for PETSCSF_LOCAL and [1] for PETSCSF_REMOTE in the following */
  for (i = 0; i < 2; i++) { /* Set defaults */
    sf->leafstart[i]   = 0;
    sf->leafcontig[i]  = PETSC_TRUE;
    sf->leafdups[i]    = PETSC_FALSE;
    bas->rootstart[i]  = 0;
    bas->rootcontig[i] = PETSC_TRUE;
    bas->rootdups[i]   = PETSC_FALSE;
  }

  sf->leafbuflen[0] = sf->roffset[sf->ndranks];
  sf->leafbuflen[1] = sf->roffset[sf->nranks] - sf->roffset[sf->ndranks];

  if (sf->leafbuflen[0]) sf->leafstart[0] = sf->rmine[0];
  if (sf->leafbuflen[1]) sf->leafstart[1] = sf->rmine[sf->roffset[sf->ndranks]];

  /* Are leaf indices for self and remote contiguous? If yes, it is best for pack/unpack */
  for (i = 0; i < sf->roffset[sf->ndranks]; i++) { /* self */
    if (sf->rmine[i] != sf->leafstart[0] + i) {
      sf->leafcontig[0] = PETSC_FALSE;
      break;
    }
  }
  for (i = sf->roffset[sf->ndranks], j = 0; i < sf->roffset[sf->nranks]; i++, j++) { /* remote */
    if (sf->rmine[i] != sf->leafstart[1] + j) {
      sf->leafcontig[1] = PETSC_FALSE;
      break;
    }
  }

  /* If not, see if we can have per-rank optimizations by doing index analysis */
  if (!sf->leafcontig[0]) PetscCall(PetscSFCreatePackOpt(sf->ndranks, sf->roffset, sf->rmine, &sf->leafpackopt[0]));
  if (!sf->leafcontig[1]) PetscCall(PetscSFCreatePackOpt(sf->nranks - sf->ndranks, sf->roffset + sf->ndranks, sf->rmine, &sf->leafpackopt[1]));

  /* Are root indices for self and remote contiguous? */
  bas->rootbuflen[0] = bas->ioffset[bas->ndiranks];
  bas->rootbuflen[1] = bas->ioffset[bas->niranks] - bas->ioffset[bas->ndiranks];

  if (bas->rootbuflen[0]) bas->rootstart[0] = bas->irootloc[0];
  if (bas->rootbuflen[1]) bas->rootstart[1] = bas->irootloc[bas->ioffset[bas->ndiranks]];

  for (i = 0; i < bas->ioffset[bas->ndiranks]; i++) {
    if (bas->irootloc[i] != bas->rootstart[0] + i) {
      bas->rootcontig[0] = PETSC_FALSE;
      break;
    }
  }
  for (i = bas->ioffset[bas->ndiranks], j = 0; i < bas->ioffset[bas->niranks]; i++, j++) {
    if (bas->irootloc[i] != bas->rootstart[1] + j) {
      bas->rootcontig[1] = PETSC_FALSE;
      break;
    }
  }

  if (!bas->rootcontig[0]) PetscCall(PetscSFCreatePackOpt(bas->ndiranks, bas->ioffset, bas->irootloc, &bas->rootpackopt[0]));
  if (!bas->rootcontig[1]) PetscCall(PetscSFCreatePackOpt(bas->niranks - bas->ndiranks, bas->ioffset + bas->ndiranks, bas->irootloc, &bas->rootpackopt[1]));

  /* Check dups in indices so that CUDA unpacking kernels can use cheaper regular instructions instead of atomics when they know there are no data race chances */
  if (PetscDefined(HAVE_DEVICE)) {
    PetscBool ismulti = (sf->multi == sf) ? PETSC_TRUE : PETSC_FALSE;
    if (!sf->leafcontig[0] && !ismulti) PetscCall(PetscCheckDupsInt(sf->leafbuflen[0], sf->rmine, &sf->leafdups[0]));
    if (!sf->leafcontig[1] && !ismulti) PetscCall(PetscCheckDupsInt(sf->leafbuflen[1], sf->rmine + sf->roffset[sf->ndranks], &sf->leafdups[1]));
    if (!bas->rootcontig[0] && !ismulti) PetscCall(PetscCheckDupsInt(bas->rootbuflen[0], bas->irootloc, &bas->rootdups[0]));
    if (!bas->rootcontig[1] && !ismulti) PetscCall(PetscCheckDupsInt(bas->rootbuflen[1], bas->irootloc + bas->ioffset[bas->ndiranks], &bas->rootdups[1]));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscSFResetPackFields(PetscSF sf)
{
  PetscSF_Basic *bas = (PetscSF_Basic *)sf->data;
  PetscInt       i;

  PetscFunctionBegin;
  for (i = PETSCSF_LOCAL; i <= PETSCSF_REMOTE; i++) {
    PetscCall(PetscSFDestroyPackOpt(sf, PETSC_MEMTYPE_HOST, &sf->leafpackopt[i]));
    PetscCall(PetscSFDestroyPackOpt(sf, PETSC_MEMTYPE_HOST, &bas->rootpackopt[i]));
#if defined(PETSC_HAVE_DEVICE)
    PetscCall(PetscSFDestroyPackOpt(sf, PETSC_MEMTYPE_DEVICE, &sf->leafpackopt_d[i]));
    PetscCall(PetscSFDestroyPackOpt(sf, PETSC_MEMTYPE_DEVICE, &bas->rootpackopt_d[i]));
#endif
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}
