xref: /petsc/src/vec/is/utils/pmap.c (revision d9126033840fa4b9e125cadad06c85976e6bf099)

/*
   This file contains routines for basic map object implementation.
*/

#include <petsc/private/isimpl.h> /*I "petscis.h" I*/

/*@
  PetscLayoutCreate - Allocates `PetscLayout` object

  Collective

  Input Parameter:
. comm - the MPI communicator

  Output Parameter:
. map - the new `PetscLayout`

  Level: advanced

  Notes:
  Typical calling sequence
.vb
       PetscLayoutCreate(MPI_Comm,PetscLayout *);
       PetscLayoutSetBlockSize(PetscLayout,bs);
       PetscLayoutSetSize(PetscLayout,N); // or PetscLayoutSetLocalSize(PetscLayout,n);
       PetscLayoutSetUp(PetscLayout);
.ve
  Alternatively,
.vb
      PetscLayoutCreateFromSizes(comm,n,N,bs,&layout);
.ve

  Optionally use any of the following
.vb
  PetscLayoutGetSize(PetscLayout,PetscInt *);
  PetscLayoutGetLocalSize(PetscLayout,PetscInt *);
  PetscLayoutGetRange(PetscLayout,PetscInt *rstart,PetscInt *rend);
  PetscLayoutGetRanges(PetscLayout,const PetscInt *range[]);
  PetscLayoutDestroy(PetscLayout*);
.ve

  The `PetscLayout` object and methods are intended to be used in the PETSc `Vec` and `Mat` implementations; it is often not needed in
  user codes unless you really gain something in their use.

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutSetLocalSize()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutGetLocalSize()`,
          `PetscLayout`, `PetscLayoutDestroy()`,
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`, `PetscLayoutSetUp()`,
          `PetscLayoutCreateFromSizes()`
@*/
PetscErrorCode PetscLayoutCreate(MPI_Comm comm, PetscLayout *map)
{
  PetscFunctionBegin;
  PetscCall(PetscNew(map));
  PetscCallMPI(MPI_Comm_size(comm, &(*map)->size));
  (*map)->comm        = comm;
  (*map)->bs          = 1;
  (*map)->n           = -1;
  (*map)->N           = -1;
  (*map)->range       = NULL;
  (*map)->range_alloc = PETSC_TRUE;
  (*map)->rstart      = 0;
  (*map)->rend        = 0;
  (*map)->setupcalled = PETSC_FALSE;
  (*map)->oldn        = -1;
  (*map)->oldN        = -1;
  (*map)->oldbs       = -1;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutCreateFromSizes - Allocates `PetscLayout` object and sets the layout sizes, and sets the layout up.

  Collective

  Input Parameters:
+ comm - the MPI communicator
. n    - the local size (or `PETSC_DECIDE`)
. N    - the global size (or `PETSC_DECIDE`)
- bs   - the block size (or `PETSC_DECIDE`)

  Output Parameter:
. map - the new `PetscLayout`

  Level: advanced

  Note:
.vb
  PetscLayoutCreateFromSizes(comm, n, N, bs, &layout);
.ve
  is a shorthand for
.vb
  PetscLayoutCreate(comm, &layout);
  PetscLayoutSetLocalSize(layout, n);
  PetscLayoutSetSize(layout, N);
  PetscLayoutSetBlockSize(layout, bs);
  PetscLayoutSetUp(layout);
.ve

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutGetLocalSize()`, `PetscLayout`, `PetscLayoutDestroy()`,
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`, `PetscLayoutSetUp()`, `PetscLayoutCreateFromRanges()`
@*/
PetscErrorCode PetscLayoutCreateFromSizes(MPI_Comm comm, PetscInt n, PetscInt N, PetscInt bs, PetscLayout *map)
{
  PetscFunctionBegin;
  PetscCall(PetscLayoutCreate(comm, map));
  PetscCall(PetscLayoutSetLocalSize(*map, n));
  PetscCall(PetscLayoutSetSize(*map, N));
  PetscCall(PetscLayoutSetBlockSize(*map, bs));
  PetscCall(PetscLayoutSetUp(*map));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutDestroy - Frees a `PetscLayout` object and frees its range if that exists.

  Collective

  Input Parameter:
. map - the `PetscLayout`

  Level: developer

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutSetLocalSize()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutGetLocalSize()`,
          `PetscLayout`, `PetscLayoutCreate()`,
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`, `PetscLayoutSetUp()`
@*/
PetscErrorCode PetscLayoutDestroy(PetscLayout *map)
{
  PetscFunctionBegin;
  if (!*map) PetscFunctionReturn(PETSC_SUCCESS);
  if (!(*map)->refcnt--) {
    if ((*map)->range_alloc) PetscCall(PetscFree((*map)->range));
    PetscCall(ISLocalToGlobalMappingDestroy(&(*map)->mapping));
    PetscCall(PetscFree(*map));
  }
  *map = NULL;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutCreateFromRanges - Creates a new `PetscLayout` with the given ownership ranges and sets it up.

  Collective

  Input Parameters:
+ comm  - the MPI communicator
. range - the array of ownership ranges for each rank with length commsize+1
. mode  - the copy mode for range
- bs    - the block size (or `PETSC_DECIDE`)

  Output Parameter:
. newmap - the new `PetscLayout`

  Level: developer

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`,
          `PetscLayoutGetLocalSize()`, `PetscLayout`, `PetscLayoutDestroy()`,
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`, `PetscLayoutSetUp()`, `PetscLayoutCreateFromSizes()`
@*/
PetscErrorCode PetscLayoutCreateFromRanges(MPI_Comm comm, const PetscInt range[], PetscCopyMode mode, PetscInt bs, PetscLayout *newmap)
{
  PetscLayout map;
  PetscMPIInt rank;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  PetscCall(PetscLayoutCreate(comm, &map));
  PetscCall(PetscLayoutSetBlockSize(map, bs));
  switch (mode) {
  case PETSC_COPY_VALUES:
    PetscCall(PetscMalloc1(map->size + 1, &map->range));
    PetscCall(PetscArraycpy(map->range, range, map->size + 1));
    break;
  case PETSC_USE_POINTER:
    map->range_alloc = PETSC_FALSE; /* fall through */
  case PETSC_OWN_POINTER:
    map->range = (PetscInt *)range;
    break;
  default:
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_PLIB, "Received invalid PetscCopyMode somehow");
  }
  map->rstart = map->range[rank];
  map->rend   = map->range[rank + 1];
  map->n      = map->rend - map->rstart;
  map->N      = map->range[map->size] - map->range[0];
  if (PetscDefined(USE_DEBUG)) { /* just check that n, N and bs are consistent */
    PetscInt tmp;
    PetscCallMPI(MPIU_Allreduce(&map->n, &tmp, 1, MPIU_INT, MPI_SUM, map->comm));
    PetscCheck(tmp == map->N, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Sum of local lengths %" PetscInt_FMT " does not equal global length %" PetscInt_FMT ", my local length %" PetscInt_FMT ". The provided PetscLayout is wrong.", tmp, map->N, map->n);
    PetscCheck(map->n % map->bs == 0, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Local size %" PetscInt_FMT " must be divisible by blocksize %" PetscInt_FMT, map->n, map->bs);
    PetscCheck(map->N % map->bs == 0, map->comm, PETSC_ERR_PLIB, "Global size %" PetscInt_FMT " must be divisible by blocksize %" PetscInt_FMT, map->N, map->bs);
  }
  /* lock the layout */
  map->setupcalled = PETSC_TRUE;
  map->oldn        = map->n;
  map->oldN        = map->N;
  map->oldbs       = map->bs;
  *newmap          = map;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutSetUp - given a map where you have set either the global or local
  size sets up the map so that it may be used.

  Collective

  Input Parameter:
. map - pointer to the map

  Level: developer

  Notes:
  Typical calling sequence
.vb
  PetscLayoutCreate(MPI_Comm,PetscLayout *);
  PetscLayoutSetBlockSize(PetscLayout,1);
  PetscLayoutSetSize(PetscLayout,n) or PetscLayoutSetLocalSize(PetscLayout,N); or both
  PetscLayoutSetUp(PetscLayout);
  PetscLayoutGetSize(PetscLayout,PetscInt *);
.ve

  If range exists, and local size is not set, everything gets computed from the range.

  If the local size, global size are already set and range exists then this does nothing.

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutSetLocalSize()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutGetLocalSize()`,
          `PetscLayout`, `PetscLayoutDestroy()`,
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`, `PetscLayoutCreate()`, `PetscSplitOwnership()`
@*/
PetscErrorCode PetscLayoutSetUp(PetscLayout map)
{
  PetscMPIInt rank;
  PetscInt    p;

  PetscFunctionBegin;
  PetscCheck(!map->setupcalled || !(map->n != map->oldn || map->N != map->oldN), map->comm, PETSC_ERR_ARG_WRONGSTATE, "Layout is already setup with (local=%" PetscInt_FMT ",global=%" PetscInt_FMT "), cannot call setup again with (local=%" PetscInt_FMT ",global=%" PetscInt_FMT ")",
             map->oldn, map->oldN, map->n, map->N);
  if (map->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);

  PetscCheck(map->n < 0 || map->n % map->bs == 0, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Local size %" PetscInt_FMT " must be divisible by blocksize %" PetscInt_FMT, map->n, map->bs);
  PetscCheck(map->N < 0 || map->N % map->bs == 0, map->comm, PETSC_ERR_PLIB, "Global size %" PetscInt_FMT " must be divisible by blocksize %" PetscInt_FMT, map->N, map->bs);

  PetscCallMPI(MPI_Comm_rank(map->comm, &rank));
  if (map->n > 0) map->n = map->n / map->bs;
  if (map->N > 0) map->N = map->N / map->bs;
  PetscCall(PetscSplitOwnership(map->comm, &map->n, &map->N));
  map->n = map->n * map->bs;
  map->N = map->N * map->bs;
  if (!map->range) PetscCall(PetscMalloc1(map->size + 1, &map->range));
  PetscCallMPI(MPI_Allgather(&map->n, 1, MPIU_INT, map->range + 1, 1, MPIU_INT, map->comm));

  map->range[0] = 0;
  for (p = 2; p <= map->size; p++) map->range[p] += map->range[p - 1];

  map->rstart = map->range[rank];
  map->rend   = map->range[rank + 1];

  /* lock the layout */
  map->setupcalled = PETSC_TRUE;
  map->oldn        = map->n;
  map->oldN        = map->N;
  map->oldbs       = map->bs;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutDuplicate - creates a new `PetscLayout` with the same information as a given one. If the `PetscLayout` already exists it is destroyed first.

  Collective

  Input Parameter:
. in - input `PetscLayout` to be duplicated

  Output Parameter:
. out - the copy

  Level: developer

  Note:
  `PetscLayoutSetUp()` does not need to be called on the resulting `PetscLayout`

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutDestroy()`, `PetscLayoutSetUp()`, `PetscLayoutReference()`
@*/
PetscErrorCode PetscLayoutDuplicate(PetscLayout in, PetscLayout *out)
{
  MPI_Comm comm = in->comm;

  PetscFunctionBegin;
  PetscCall(PetscLayoutDestroy(out));
  PetscCall(PetscLayoutCreate(comm, out));
  PetscCall(PetscMemcpy(*out, in, sizeof(struct _n_PetscLayout)));
  if (in->range) {
    PetscCall(PetscMalloc1((*out)->size + 1, &(*out)->range));
    PetscCall(PetscArraycpy((*out)->range, in->range, (*out)->size + 1));
  }
  (*out)->refcnt = 0;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutReference - Causes a PETSc `Vec` or `Mat` to share a `PetscLayout` with one that already exists.

  Collective

  Input Parameter:
. in - input `PetscLayout` to be copied

  Output Parameter:
. out - the reference location

  Level: developer

  Notes:
  `PetscLayoutSetUp()` does not need to be called on the resulting `PetscLayout`

  If the out location already contains a `PetscLayout` it is destroyed

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutDestroy()`, `PetscLayoutSetUp()`, `PetscLayoutDuplicate()`
@*/
PetscErrorCode PetscLayoutReference(PetscLayout in, PetscLayout *out)
{
  PetscFunctionBegin;
  in->refcnt++;
  PetscCall(PetscLayoutDestroy(out));
  *out = in;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutSetISLocalToGlobalMapping - sets a `ISLocalGlobalMapping` into a `PetscLayout`

  Collective

  Input Parameters:
+ in   - input `PetscLayout`
- ltog - the local to global mapping

  Level: developer

  Notes:
  `PetscLayoutSetUp()` does not need to be called on the resulting `PetscLayout`

  If the `PetscLayout` already contains a `ISLocalGlobalMapping` it is destroyed

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutDestroy()`, `PetscLayoutSetUp()`, `PetscLayoutDuplicate()`
@*/
PetscErrorCode PetscLayoutSetISLocalToGlobalMapping(PetscLayout in, ISLocalToGlobalMapping ltog)
{
  PetscFunctionBegin;
  if (ltog) {
    PetscInt bs;

    PetscCall(ISLocalToGlobalMappingGetBlockSize(ltog, &bs));
    PetscCheck(in->bs == 1 || bs == 1 || in->bs == bs, in->comm, PETSC_ERR_PLIB, "Blocksize of layout %" PetscInt_FMT " must match that of mapping %" PetscInt_FMT " (or the latter must be 1)", in->bs, bs);
  }
  PetscCall(PetscObjectReference((PetscObject)ltog));
  PetscCall(ISLocalToGlobalMappingDestroy(&in->mapping));
  in->mapping = ltog;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutSetLocalSize - Sets the local size for a `PetscLayout` object.

  Collective

  Input Parameters:
+ map - pointer to the map
- n   - the local size, pass `PETSC_DECIDE` (the default) to have this value determined by the global size set with `PetscLayoutSetSize()`

  Level: developer

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutSetUp()`
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`
@*/
PetscErrorCode PetscLayoutSetLocalSize(PetscLayout map, PetscInt n)
{
  PetscFunctionBegin;
  PetscCheck(n % map->bs == 0, map->comm, PETSC_ERR_ARG_INCOMP, "Local size %" PetscInt_FMT " not compatible with block size %" PetscInt_FMT, n, map->bs);
  map->n = n;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutGetLocalSize - Gets the local size for a `PetscLayout` object.

  Not Collective

  Input Parameter:
. map - pointer to the map

  Output Parameter:
. n - the local size

  Level: developer

  Note:
  Call this after the call to `PetscLayoutSetUp()`

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutSetUp()`
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`
@*/
PetscErrorCode PetscLayoutGetLocalSize(PetscLayout map, PetscInt *n)
{
  PetscFunctionBegin;
  *n = map->n;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutSetSize - Sets the global size for a `PetscLayout` object.

  Logically Collective

  Input Parameters:
+ map - pointer to the map
- n   - the global size, use `PETSC_DETERMINE` (the default) to have this value computed as the sum of the local sizes set with `PetscLayoutSetLocalSize()`

  Level: developer

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutGetSize()`, `PetscLayoutSetUp()`
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`
@*/
PetscErrorCode PetscLayoutSetSize(PetscLayout map, PetscInt n)
{
  PetscFunctionBegin;
  map->N = n;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutGetSize - Gets the global size for a `PetscLayout` object.

  Not Collective

  Input Parameter:
. map - pointer to the map

  Output Parameter:
. n - the global size

  Level: developer

  Note:
  Call this after the call to `PetscLayoutSetUp()`

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutSetSize()`, `PetscLayoutSetUp()`
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetBlockSize()`
@*/
PetscErrorCode PetscLayoutGetSize(PetscLayout map, PetscInt *n)
{
  PetscFunctionBegin;
  *n = map->N;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutSetBlockSize - Sets the block size for a `PetscLayout` object.

  Logically Collective

  Input Parameters:
+ map - pointer to the map
- bs  - the size

  Level: developer

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutGetBlockSize()`,
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutSetUp()`
@*/
PetscErrorCode PetscLayoutSetBlockSize(PetscLayout map, PetscInt bs)
{
  PetscFunctionBegin;
  PetscCheck(bs > 0, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "Block size %" PetscInt_FMT " must be positive", bs);
  PetscCheck(map->n <= 0 || (map->n % bs) == 0, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "Local size %" PetscInt_FMT " not compatible with block size %" PetscInt_FMT, map->n, bs);
  if (map->mapping) {
    PetscInt obs;

    PetscCall(ISLocalToGlobalMappingGetBlockSize(map->mapping, &obs));
    if (obs > 1) PetscCall(ISLocalToGlobalMappingSetBlockSize(map->mapping, bs));
  }
  map->bs = bs;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutGetBlockSize - Gets the block size for a `PetscLayout` object.

  Not Collective

  Input Parameter:
. map - pointer to the map

  Output Parameter:
. bs - the size

  Level: developer

  Notes:
  Call this after the call to `PetscLayoutSetUp()`

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutSetSize()`, `PetscLayoutSetUp()`
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutGetSize()`
@*/
PetscErrorCode PetscLayoutGetBlockSize(PetscLayout map, PetscInt *bs)
{
  PetscFunctionBegin;
  *bs = map->bs;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutGetRange - gets the range of values owned by this process

  Not Collective

  Input Parameter:
. map - pointer to the map

  Output Parameters:
+ rstart - first index owned by this process
- rend   - one more than the last index owned by this process

  Level: developer

  Note:
  Call this after the call to `PetscLayoutSetUp()`

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutSetSize()`,
          `PetscLayoutGetSize()`, `PetscLayoutGetRanges()`, `PetscLayoutSetBlockSize()`, `PetscLayoutSetUp()`
@*/
PetscErrorCode PetscLayoutGetRange(PetscLayout map, PetscInt *rstart, PetscInt *rend)
{
  PetscFunctionBegin;
  if (rstart) *rstart = map->rstart;
  if (rend) *rend = map->rend;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscLayoutGetRanges - gets the ranges of values owned by all processes

  Not Collective

  Input Parameter:
. map - pointer to the map

  Output Parameter:
. range - start of each processors range of indices (the final entry is one more than the
          last index on the last process). The length of the array is one more than the number of processes in the MPI
          communicator owned by `map`

  Level: developer

  Note:
  Call this after the call to `PetscLayoutSetUp()`

  Fortran Notes:
.vb
  PetscInt, pointer :: range(:)
.ve

  Call `PetscLayoutRestoreRanges()` when no longer needed.

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutSetSize()`,
          `PetscLayoutGetSize()`, `PetscLayoutGetRange()`, `PetscLayoutSetBlockSize()`, `PetscLayoutSetUp()`
@*/
PetscErrorCode PetscLayoutGetRanges(PetscLayout map, const PetscInt *range[])
{
  PetscFunctionBegin;
  *range = map->range;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutCompare - Compares two layouts

  Not Collective

  Input Parameters:
+ mapa - pointer to the first map
- mapb - pointer to the second map

  Output Parameter:
. congruent - `PETSC_TRUE` if the two layouts are congruent, `PETSC_FALSE` otherwise

  Level: beginner

.seealso: [PetscLayout](sec_matlayout), `PetscLayoutCreate()`, `PetscLayoutSetLocalSize()`, `PetscLayoutGetLocalSize()`, `PetscLayoutGetBlockSize()`,
          `PetscLayoutGetRange()`, `PetscLayoutGetRanges()`, `PetscLayoutSetSize()`, `PetscLayoutGetSize()`, `PetscLayoutSetUp()`
@*/
PetscErrorCode PetscLayoutCompare(PetscLayout mapa, PetscLayout mapb, PetscBool *congruent)
{
  PetscFunctionBegin;
  *congruent = PETSC_FALSE;
  if (mapa->N == mapb->N && mapa->range && mapb->range && mapa->size == mapb->size) PetscCall(PetscArraycmp(mapa->range, mapb->range, mapa->size + 1, congruent));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutFindOwner - Find the owning MPI process for a global index

  Not Collective; No Fortran Support

  Input Parameters:
+ map - the layout
- idx - global index to find the owner of

  Output Parameter:
. owner - the owning rank

  Level: developer

.seealso: `PetscLayout`, `PetscLayoutFindOwnerIndex()`
@*/
PetscErrorCode PetscLayoutFindOwner(PetscLayout map, PetscInt idx, PetscMPIInt *owner)
{
  PetscMPIInt lo = 0, hi, t;

  PetscFunctionBegin;
  *owner = -1; /* GCC erroneously issues warning about possibly uninitialized use when error condition */
  PetscAssert((map->n >= 0) && (map->N >= 0) && (map->range), PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "PetscLayoutSetUp() must be called first");
  PetscAssert(idx >= 0 && idx <= map->N, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Index %" PetscInt_FMT " is out of range", idx);
  hi = map->size;
  while (hi - lo > 1) {
    t = lo + (hi - lo) / 2;
    if (idx < map->range[t]) hi = t;
    else lo = t;
  }
  *owner = lo;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@
  PetscLayoutFindOwnerIndex - Find the owning MPI process and the local index on that process for a global index

  Not Collective; No Fortran Support

  Input Parameters:
+ map - the layout
- idx - global index to find the owner of

  Output Parameters:
+ owner - the owning rank
- lidx  - local index used by the owner for `idx`

  Level: developer

.seealso: `PetscLayout`, `PetscLayoutFindOwner()`
@*/
PetscErrorCode PetscLayoutFindOwnerIndex(PetscLayout map, PetscInt idx, PetscMPIInt *owner, PetscInt *lidx)
{
  PetscMPIInt lo = 0, hi, t;

  PetscFunctionBegin;
  PetscAssert((map->n >= 0) && (map->N >= 0) && (map->range), PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "PetscLayoutSetUp() must be called first");
  PetscAssert(idx >= 0 && idx <= map->N, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Index %" PetscInt_FMT " is out of range", idx);
  hi = map->size;
  while (hi - lo > 1) {
    t = lo + (hi - lo) / 2;
    if (idx < map->range[t]) hi = t;
    else lo = t;
  }
  if (owner) *owner = lo;
  if (lidx) *lidx = idx - map->range[lo];
  PetscFunctionReturn(PETSC_SUCCESS);
}