Actual source code: mpiu.c

      1: #include <petscsys.h>
      2: #include <petsc/private/petscimpl.h>
      3: /*
      4:     Note that tag of 0 is ok because comm is a private communicator
      5:   generated below just for these routines.
      6: */

      8: PETSC_INTERN PetscErrorCode PetscSequentialPhaseBegin_Private(MPI_Comm comm, int ng)
      9: {
     10:   PetscMPIInt rank, size, tag = 0;
     11:   MPI_Status  status;

     13:   PetscFunctionBegin;
     14:   PetscCallMPI(MPI_Comm_size(comm, &size));
     15:   if (size == 1) PetscFunctionReturn(PETSC_SUCCESS);
     16:   PetscCallMPI(MPI_Comm_rank(comm, &rank));
     17:   if (rank) PetscCallMPI(MPI_Recv(NULL, 0, MPI_INT, rank - 1, tag, comm, &status));
     18:   /* Send to the next process in the group unless we are the last process */
     19:   if ((rank % ng) < ng - 1 && rank != size - 1) PetscCallMPI(MPI_Send(NULL, 0, MPI_INT, rank + 1, tag, comm));
     20:   PetscFunctionReturn(PETSC_SUCCESS);
     21: }

     23: PETSC_INTERN PetscErrorCode PetscSequentialPhaseEnd_Private(MPI_Comm comm, int ng)
     24: {
     25:   PetscMPIInt rank, size, tag = 0;
     26:   MPI_Status  status;

     28:   PetscFunctionBegin;
     29:   PetscCallMPI(MPI_Comm_rank(comm, &rank));
     30:   PetscCallMPI(MPI_Comm_size(comm, &size));
     31:   if (size == 1) PetscFunctionReturn(PETSC_SUCCESS);

     33:   /* Send to the first process in the next group */
     34:   if ((rank % ng) == ng - 1 || rank == size - 1) PetscCallMPI(MPI_Send(NULL, 0, MPI_INT, (rank + 1) % size, tag, comm));
     35:   if (rank == 0) PetscCallMPI(MPI_Recv(NULL, 0, MPI_INT, size - 1, tag, comm, &status));
     36:   PetscFunctionReturn(PETSC_SUCCESS);
     37: }

     39: /*
     40:     The variable Petsc_Seq_keyval is used to indicate an MPI attribute that
     41:   is attached to a communicator that manages the sequential phase code below.
     42: */
     43: PetscMPIInt Petsc_Seq_keyval = MPI_KEYVAL_INVALID;

     45: /*@
     46:   PetscSequentialPhaseBegin - Begins a sequential section of code.

     48:   Collective

     50:   Input Parameters:
     51: + comm - Communicator to sequentialize over
     52: - ng   - Number in processor group.  This many processes are allowed to execute
     53:    at the same time (usually 1)

     55:   Level: intermediate

     57:   Notes:
     58:   `PetscSequentialPhaseBegin()` and `PetscSequentialPhaseEnd()` provide a
     59:   way to force a section of code to be executed by the processes in
     60:   rank order.  Typically, this is done with
     61: .vb
     62:       PetscSequentialPhaseBegin(comm, 1);
     63:       <code to be executed sequentially>
     64:       PetscSequentialPhaseEnd(comm, 1);
     65: .ve

     67:   You should use `PetscSynchronizedPrintf()` to ensure output between MPI ranks is properly order and not these routines.

     69: .seealso: `PetscSequentialPhaseEnd()`, `PetscSynchronizedPrintf()`
     70: @*/
     71: PetscErrorCode PetscSequentialPhaseBegin(MPI_Comm comm, int ng)
     72: {
     73:   PetscMPIInt size;
     74:   MPI_Comm    local_comm, *addr_local_comm;

     76:   PetscFunctionBegin;
     77:   PetscCall(PetscSysInitializePackage());
     78:   PetscCallMPI(MPI_Comm_size(comm, &size));
     79:   if (size == 1) PetscFunctionReturn(PETSC_SUCCESS);

     81:   /* Get the private communicator for the sequential operations */
     82:   if (Petsc_Seq_keyval == MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_create_keyval(MPI_COMM_NULL_COPY_FN, MPI_COMM_NULL_DELETE_FN, &Petsc_Seq_keyval, NULL));

     84:   PetscCallMPI(MPI_Comm_dup(comm, &local_comm));
     85:   PetscCall(PetscMalloc1(1, &addr_local_comm));

     87:   *addr_local_comm = local_comm;

     89:   PetscCallMPI(MPI_Comm_set_attr(comm, Petsc_Seq_keyval, (void *)addr_local_comm));
     90:   PetscCall(PetscSequentialPhaseBegin_Private(local_comm, ng));
     91:   PetscFunctionReturn(PETSC_SUCCESS);
     92: }

     94: /*@
     95:   PetscSequentialPhaseEnd - Ends a sequential section of code.

     97:   Collective

     99:   Input Parameters:
    100: + comm - Communicator to sequentialize.
    101: - ng   - Number in processor group.  This many processes are allowed to execute
    102:    at the same time (usually 1)

    104:   Level: intermediate

    106:   Note:
    107:   See `PetscSequentialPhaseBegin()` for more details.

    109: .seealso: `PetscSequentialPhaseBegin()`
    110: @*/
    111: PetscErrorCode PetscSequentialPhaseEnd(MPI_Comm comm, int ng)
    112: {
    113:   PetscMPIInt size, iflg;
    114:   MPI_Comm    local_comm, *addr_local_comm;

    116:   PetscFunctionBegin;
    117:   PetscCallMPI(MPI_Comm_size(comm, &size));
    118:   if (size == 1) PetscFunctionReturn(PETSC_SUCCESS);

    120:   PetscCallMPI(MPI_Comm_get_attr(comm, Petsc_Seq_keyval, (void **)&addr_local_comm, &iflg));
    121:   PetscCheck(iflg, PETSC_COMM_SELF, PETSC_ERR_ARG_INCOMP, "Wrong MPI communicator; must pass in one used with PetscSequentialPhaseBegin()");
    122:   local_comm = *addr_local_comm;

    124:   PetscCall(PetscSequentialPhaseEnd_Private(local_comm, ng));

    126:   PetscCall(PetscFree(addr_local_comm));
    127:   PetscCallMPI(MPI_Comm_free(&local_comm));
    128:   PetscCallMPI(MPI_Comm_delete_attr(comm, Petsc_Seq_keyval));
    129:   PetscFunctionReturn(PETSC_SUCCESS);
    130: }

    132: /*@
    133:   PetscGlobalMinMaxInt - Get the global min/max from local min/max input

    135:   Collective

    137:   Input Parameters:
    138: + comm      - The MPI communicator to reduce with
    139: - minMaxVal - An array with the local min and max

    141:   Output Parameter:
    142: . minMaxValGlobal - An array with the global min and max

    144:   Level: beginner

    146: .seealso: `PetscSplitOwnership()`, `PetscGlobalMinMaxReal()`
    147: @*/
    148: PetscErrorCode PetscGlobalMinMaxInt(MPI_Comm comm, const PetscInt minMaxVal[2], PetscInt minMaxValGlobal[2])
    149: {
    150:   PetscInt  sendbuf[3], recvbuf[3];
    151:   PetscBool hasminint = (PetscBool)(minMaxVal[0] == PETSC_MIN_INT);

    153:   PetscFunctionBegin;
    154:   sendbuf[0] = hasminint ? PETSC_MIN_INT : -minMaxVal[0]; /* Note that -PETSC_INT_MIN = PETSC_INT_MIN: ternary to suppress sanitizer warnings */
    155:   sendbuf[1] = minMaxVal[1];
    156:   sendbuf[2] = hasminint ? 1 : 0; /* Are there PETSC_INT_MIN in minMaxVal[0]? */
    157:   PetscCallMPI(MPIU_Allreduce(sendbuf, recvbuf, 3, MPIU_INT, MPI_MAX, comm));
    158:   minMaxValGlobal[0] = recvbuf[2] ? PETSC_INT_MIN : -recvbuf[0];
    159:   minMaxValGlobal[1] = recvbuf[1];
    160:   PetscFunctionReturn(PETSC_SUCCESS);
    161: }

    163: /*@
    164:   PetscGlobalMinMaxReal - Get the global min/max from local min/max input

    166:   Collective

    168:   Input Parameters:
    169: + comm      - The MPI communicator to reduce with
    170: - minMaxVal - An array with the local min and max

    172:   Output Parameter:
    173: . minMaxValGlobal - An array with the global min and max

    175:   Level: beginner

    177: .seealso: `PetscSplitOwnership()`, `PetscGlobalMinMaxInt()`
    178: @*/
    179: PetscErrorCode PetscGlobalMinMaxReal(MPI_Comm comm, const PetscReal minMaxVal[2], PetscReal minMaxValGlobal[2])
    180: {
    181:   PetscReal sendbuf[2];

    183:   PetscFunctionBegin;
    184:   sendbuf[0] = -minMaxVal[0];
    185:   sendbuf[1] = minMaxVal[1];
    186:   PetscCallMPI(MPIU_Allreduce(sendbuf, minMaxValGlobal, 2, MPIU_REAL, MPIU_MAX, comm));
    187:   minMaxValGlobal[0] = -minMaxValGlobal[0];
    188:   PetscFunctionReturn(PETSC_SUCCESS);
    189: }