Actual source code: mpishm.c

  1: #include <petscsys.h>
  2: #include <petsc/private/petscimpl.h>

  4: struct _n_PetscShmComm {
  5:   PetscMPIInt *globranks;         /* global ranks of each rank in the shared memory communicator */
  6:   PetscMPIInt  shmsize;           /* size of the shared memory communicator */
  7:   MPI_Comm     globcomm, shmcomm; /* global communicator and shared memory communicator (a sub-communicator of the former) */
  8: };

 10: /*
 11:    Private routine to delete internal shared memory communicator when a communicator is freed.

 13:    This is called by MPI, not by users. This is called by MPI_Comm_free() when the communicator that has this  data as an attribute is freed.

 15:    Note: this is declared extern "C" because it is passed to MPI_Comm_create_keyval()

 17: */
 18: PETSC_EXTERN PetscMPIInt MPIAPI Petsc_ShmComm_Attr_DeleteFn(MPI_Comm comm, PetscMPIInt keyval, void *val, void *extra_state)
 19: {
 20:   PetscShmComm p = (PetscShmComm)val;

 22:   PetscFunctionBegin;
 23:   PetscCallReturnMPI(PetscInfo(NULL, "Deleting shared memory subcommunicator in a MPI_Comm %ld\n", (long)comm));
 24:   PetscCallMPIReturnMPI(MPI_Comm_free(&p->shmcomm));
 25:   PetscCallReturnMPI(PetscFree(p->globranks));
 26:   PetscCallReturnMPI(PetscFree(val));
 27:   PetscFunctionReturn(MPI_SUCCESS);
 28: }

 30: #ifdef PETSC_HAVE_MPI_PROCESS_SHARED_MEMORY
 31:   /* Data structures to support freeing comms created in PetscShmCommGet().
 32:   Since we predict communicators passed to PetscShmCommGet() are very likely
 33:   either a PETSc inner communicator or an MPI communicator with a linked PETSc
 34:   inner communicator, we use a simple static array to store dupped communicators
 35:   on rare cases otherwise.
 36:  */
 37:   #define MAX_SHMCOMM_DUPPED_COMMS 16
 38: static PetscInt       num_dupped_comms = 0;
 39: static MPI_Comm       shmcomm_dupped_comms[MAX_SHMCOMM_DUPPED_COMMS];
 40: static PetscErrorCode PetscShmCommDestroyDuppedComms(void)
 41: {
 42:   PetscFunctionBegin;
 43:   for (PetscInt i = 0; i < num_dupped_comms; i++) PetscCall(PetscCommDestroy(&shmcomm_dupped_comms[i]));
 44:   num_dupped_comms = 0; /* reset so that PETSc can be reinitialized */
 45:   PetscFunctionReturn(PETSC_SUCCESS);
 46: }
 47: #endif

 49: /*@C
 50:   PetscShmCommGet - Returns a sub-communicator of all ranks that share a common memory

 52:   Collective.

 54:   Input Parameter:
 55: . globcomm - `MPI_Comm`, which can be a user `MPI_Comm` or a PETSc inner `MPI_Comm`

 57:   Output Parameter:
 58: . pshmcomm - the PETSc shared memory communicator object

 60:   Level: developer

 62:   Note:
 63:   When used with MPICH, MPICH must be configured with `--download-mpich-device=ch3:nemesis`

 65: .seealso: `PetscShmCommGlobalToLocal()`, `PetscShmCommLocalToGlobal()`, `PetscShmCommGetMpiShmComm()`
 66: @*/
 67: PetscErrorCode PetscShmCommGet(MPI_Comm globcomm, PetscShmComm *pshmcomm)
 68: {
 69: #ifdef PETSC_HAVE_MPI_PROCESS_SHARED_MEMORY
 70:   MPI_Group         globgroup, shmgroup;
 71:   PetscMPIInt      *shmranks, i, flg;
 72:   PetscCommCounter *counter;

 74:   PetscFunctionBegin;
 75:   PetscAssertPointer(pshmcomm, 2);
 76:   /* Get a PETSc inner comm, since we always want to stash pshmcomm on PETSc inner comms */
 77:   PetscCallMPI(MPI_Comm_get_attr(globcomm, Petsc_Counter_keyval, &counter, &flg));
 78:   if (!flg) { /* globcomm is not a PETSc comm */
 79:     union
 80:     {
 81:       MPI_Comm comm;
 82:       void    *ptr;
 83:     } ucomm;
 84:     /* check if globcomm already has a linked PETSc inner comm */
 85:     PetscCallMPI(MPI_Comm_get_attr(globcomm, Petsc_InnerComm_keyval, &ucomm, &flg));
 86:     if (!flg) {
 87:       /* globcomm does not have a linked PETSc inner comm, so we create one and replace globcomm with it */
 88:       PetscCheck(num_dupped_comms < MAX_SHMCOMM_DUPPED_COMMS, globcomm, PETSC_ERR_PLIB, "PetscShmCommGet() is trying to dup more than %d MPI_Comms", MAX_SHMCOMM_DUPPED_COMMS);
 89:       PetscCall(PetscCommDuplicate(globcomm, &globcomm, NULL));
 90:       /* Register a function to free the dupped PETSc comms at PetscFinalize() at the first time */
 91:       if (num_dupped_comms == 0) PetscCall(PetscRegisterFinalize(PetscShmCommDestroyDuppedComms));
 92:       shmcomm_dupped_comms[num_dupped_comms] = globcomm;
 93:       num_dupped_comms++;
 94:     } else {
 95:       /* otherwise, we pull out the inner comm and use it as globcomm */
 96:       globcomm = ucomm.comm;
 97:     }
 98:   }

100:   /* Check if globcomm already has an attached pshmcomm. If no, create one */
101:   PetscCallMPI(MPI_Comm_get_attr(globcomm, Petsc_ShmComm_keyval, pshmcomm, &flg));
102:   if (flg) PetscFunctionReturn(PETSC_SUCCESS);

104:   PetscCall(PetscNew(pshmcomm));
105:   (*pshmcomm)->globcomm = globcomm;

107:   PetscCallMPI(MPI_Comm_split_type(globcomm, MPI_COMM_TYPE_SHARED, 0, MPI_INFO_NULL, &(*pshmcomm)->shmcomm));

109:   PetscCallMPI(MPI_Comm_size((*pshmcomm)->shmcomm, &(*pshmcomm)->shmsize));
110:   PetscCallMPI(MPI_Comm_group(globcomm, &globgroup));
111:   PetscCallMPI(MPI_Comm_group((*pshmcomm)->shmcomm, &shmgroup));
112:   PetscCall(PetscMalloc1((*pshmcomm)->shmsize, &shmranks));
113:   PetscCall(PetscMalloc1((*pshmcomm)->shmsize, &(*pshmcomm)->globranks));
114:   for (i = 0; i < (*pshmcomm)->shmsize; i++) shmranks[i] = i;
115:   PetscCallMPI(MPI_Group_translate_ranks(shmgroup, (*pshmcomm)->shmsize, shmranks, globgroup, (*pshmcomm)->globranks));
116:   PetscCall(PetscFree(shmranks));
117:   PetscCallMPI(MPI_Group_free(&globgroup));
118:   PetscCallMPI(MPI_Group_free(&shmgroup));

120:   for (i = 0; i < (*pshmcomm)->shmsize; i++) PetscCall(PetscInfo(NULL, "Shared memory rank %d global rank %d\n", i, (*pshmcomm)->globranks[i]));
121:   PetscCallMPI(MPI_Comm_set_attr(globcomm, Petsc_ShmComm_keyval, *pshmcomm));
122:   PetscFunctionReturn(PETSC_SUCCESS);
123: #else
124:   SETERRQ(globcomm, PETSC_ERR_SUP, "Shared memory communicators need MPI-3 package support.\nPlease upgrade your MPI or reconfigure with --download-mpich.");
125: #endif
126: }

128: /*@C
129:   PetscShmCommGlobalToLocal - Given a global rank returns the local rank in the shared memory communicator

131:   Input Parameters:
132: + pshmcomm - the shared memory communicator object
133: - grank    - the global rank

135:   Output Parameter:
136: . lrank - the local rank, or `MPI_PROC_NULL` if it does not exist

138:   Level: developer

140:   Developer Notes:
141:   Assumes the pshmcomm->globranks[] is sorted

143:   It may be better to rewrite this to map multiple global ranks to local in the same function call

145: .seealso: `PetscShmCommGet()`, `PetscShmCommLocalToGlobal()`, `PetscShmCommGetMpiShmComm()`
146: @*/
147: PetscErrorCode PetscShmCommGlobalToLocal(PetscShmComm pshmcomm, PetscMPIInt grank, PetscMPIInt *lrank)
148: {
149:   PetscMPIInt low, high, t, i;
150:   PetscBool   flg = PETSC_FALSE;

152:   PetscFunctionBegin;
153:   PetscAssertPointer(pshmcomm, 1);
154:   PetscAssertPointer(lrank, 3);
155:   *lrank = MPI_PROC_NULL;
156:   if (grank < pshmcomm->globranks[0]) PetscFunctionReturn(PETSC_SUCCESS);
157:   if (grank > pshmcomm->globranks[pshmcomm->shmsize - 1]) PetscFunctionReturn(PETSC_SUCCESS);
158:   PetscCall(PetscOptionsGetBool(NULL, NULL, "-noshared", &flg, NULL));
159:   if (flg) PetscFunctionReturn(PETSC_SUCCESS);
160:   low  = 0;
161:   high = pshmcomm->shmsize;
162:   while (high - low > 5) {
163:     t = (low + high) / 2;
164:     if (pshmcomm->globranks[t] > grank) high = t;
165:     else low = t;
166:   }
167:   for (i = low; i < high; i++) {
168:     if (pshmcomm->globranks[i] > grank) PetscFunctionReturn(PETSC_SUCCESS);
169:     if (pshmcomm->globranks[i] == grank) {
170:       *lrank = i;
171:       PetscFunctionReturn(PETSC_SUCCESS);
172:     }
173:   }
174:   PetscFunctionReturn(PETSC_SUCCESS);
175: }

177: /*@C
178:   PetscShmCommLocalToGlobal - Given a local rank in the shared memory communicator returns the global rank

180:   Input Parameters:
181: + pshmcomm - the shared memory communicator object
182: - lrank    - the local rank in the shared memory communicator

184:   Output Parameter:
185: . grank - the global rank in the global communicator where the shared memory communicator is built

187:   Level: developer

189: .seealso: `PetscShmCommGlobalToLocal()`, `PetscShmCommGet()`, `PetscShmCommGetMpiShmComm()`
190: @*/
191: PetscErrorCode PetscShmCommLocalToGlobal(PetscShmComm pshmcomm, PetscMPIInt lrank, PetscMPIInt *grank)
192: {
193:   PetscFunctionBegin;
194:   PetscAssertPointer(pshmcomm, 1);
195:   PetscAssertPointer(grank, 3);
196:   PetscCheck(lrank >= 0 && lrank < pshmcomm->shmsize, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "No rank %d in the shared memory communicator", lrank);
197:   *grank = pshmcomm->globranks[lrank];
198:   PetscFunctionReturn(PETSC_SUCCESS);
199: }

201: /*@C
202:   PetscShmCommGetMpiShmComm - Returns the MPI communicator that represents all processes with common shared memory

204:   Input Parameter:
205: . pshmcomm - PetscShmComm object obtained with PetscShmCommGet()

207:   Output Parameter:
208: . comm - the MPI communicator

210:   Level: developer

212: .seealso: `PetscShmCommGlobalToLocal()`, `PetscShmCommGet()`, `PetscShmCommLocalToGlobal()`
213: @*/
214: PetscErrorCode PetscShmCommGetMpiShmComm(PetscShmComm pshmcomm, MPI_Comm *comm)
215: {
216:   PetscFunctionBegin;
217:   PetscAssertPointer(pshmcomm, 1);
218:   PetscAssertPointer(comm, 2);
219:   *comm = pshmcomm->shmcomm;
220:   PetscFunctionReturn(PETSC_SUCCESS);
221: }