1: #pragma once

  3: /* SUBMANSEC = PetscSF */

  5: /*S
  6:    PetscSF - PETSc object for setting up and managing the communication of certain entries of arrays and `Vec` between MPI ranks.

  8:    Level: intermediate

 10:   `PetscSF` uses the concept of star forests to indicate and determine the communication patterns concisely and efficiently.
 11:   A star  <https://en.wikipedia.org/wiki/Star_(graph_theory)> forest is simply a collection of trees of height 1. The leave nodes represent
 12:   "ghost locations" for the root nodes.

 14: .seealso: `PetscSFCreate()`, `VecScatter`, `VecScatterCreate()`
 15: S*/
 16: typedef struct _p_PetscSF *PetscSF;

 18: /*J
 19:     PetscSFType - String with the name of a `PetscSF` type

 21:    Level: beginner

 23: .seealso: `PetscSFSetType()`, `PetscSF`
 24: J*/
 25: typedef const char *PetscSFType;
 26: #define PETSCSFBASIC      "basic"
 27: #define PETSCSFNEIGHBOR   "neighbor"
 28: #define PETSCSFALLGATHERV "allgatherv"
 29: #define PETSCSFALLGATHER  "allgather"
 30: #define PETSCSFGATHERV    "gatherv"
 31: #define PETSCSFGATHER     "gather"
 32: #define PETSCSFALLTOALL   "alltoall"
 33: #define PETSCSFWINDOW     "window"

 35: /*S
 36:    PetscSFNode - specifier of owner and index

 38:    Level: beginner

 40:   Sample Usage:
 41: .vb
 42:     PetscSFNode    *remote;
 43:     PetscCall(PetscMalloc1(nleaves,&remote));
 44:     for (i=0; i<size; i++) {
 45:       remote[i].rank = i;
 46:       remote[i].index = rank;
 47:     }
 48: .ve

 50:   Sample Fortran Usage:
 51: .vb
 52:     type(PetscSFNode) remote(6)
 53:     remote(1)%rank  = modulo(rank+size-1,size)
 54:     remote(1)%index = 1 * stride
 55: .ve

 57:   Notes:
 58:   Use  `MPIU_SF_NODE` when performing MPI operations on arrays of `PetscSFNode`

 60:   Generally the values of `rank` should be in $[ 0,size)$  and the value of `index` greater than or equal to 0, but there are some situations that violate this.

 62: .seealso: `PetscSF`, `PetscSFSetGraph()`
 63: S*/
 64: typedef struct {
 65:   PetscInt rank;  /* Rank of owner */
 66:   PetscInt index; /* Index of node on rank */
 67: } PetscSFNode;

 69: #define MPIU_SF_NODE MPIU_2INT

 71: /*S
 72:      VecScatter - Object used to manage communication of data
 73:      between vectors in parallel. Manages both scatters and gathers

 75:    Level: beginner

 77: .seealso: `Vec`, `PetscSF`, `VecScatterCreate()`, `VecScatterBegin()`, `VecScatterEnd()`
 78: S*/
 79: typedef PetscSF VecScatter;

 81: /*J
 82:    VecScatterType - String with the name of a PETSc vector scatter type

 84:    Level: beginner

 86: .seealso: `PetscSFType`, `VecScatterSetType()`, `VecScatter`, `VecScatterCreate()`, `VecScatterDestroy()`
 87: J*/
 88: typedef PetscSFType VecScatterType;