Actual source code: tagm.c

petsc-main 2021-03-01
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  1: #include <petsc/private/petscimpl.h>
  2: /* ---------------------------------------------------------------- */
  3: /*
  4:    A simple way to manage tags inside a communicator.

  6:    It uses the attributes to determine if a new communicator
  7:       is needed and to store the available tags.

  9: */


 12: /*@C
 13:     PetscObjectGetNewTag - Gets a unique new tag from a PETSc object. All
 14:     processors that share the object MUST call this routine EXACTLY the same
 15:     number of times.  This tag should only be used with the current objects
 16:     communicator; do NOT use it with any other MPI communicator.

 18:     Collective on PetscObject

 20:     Input Parameter:
 21: .   obj - the PETSc object; this must be cast with a (PetscObject), for example,
 22:          PetscObjectGetNewTag((PetscObject)mat,&tag);

 24:     Output Parameter:
 25: .   tag - the new tag

 27:     Level: developer

 29: .seealso: PetscCommGetNewTag()
 30: @*/
 31: PetscErrorCode  PetscObjectGetNewTag(PetscObject obj,PetscMPIInt *tag)
 32: {

 36:   PetscCommGetNewTag(obj->comm,tag);
 37:   return(0);
 38: }

 40: /*@
 41:     PetscCommGetNewTag - Gets a unique new tag from a PETSc communicator. All
 42:     processors that share the communicator MUST call this routine EXACTLY the same
 43:     number of times.  This tag should only be used with the current objects
 44:     communicator; do NOT use it with any other MPI communicator.

 46:     Collective

 48:     Input Parameter:
 49: .   comm - the MPI communicator

 51:     Output Parameter:
 52: .   tag - the new tag

 54:     Level: developer

 56: .seealso: PetscObjectGetNewTag(), PetscCommDuplicate()
 57: @*/
 58: PetscErrorCode  PetscCommGetNewTag(MPI_Comm comm,PetscMPIInt *tag)
 59: {
 60:   PetscErrorCode   ierr;
 61:   PetscCommCounter *counter;
 62:   PetscMPIInt      *maxval,flg;


 67:   MPI_Comm_get_attr(comm,Petsc_Counter_keyval,&counter,&flg);
 68:   if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_CORRUPT,"Bad MPI communicator supplied; must be a PETSc communicator");

 70:   if (counter->tag < 1) {
 71:     PetscInfo1(NULL,"Out of tags for object, starting to recycle. Comm reference count %d\n",counter->refcount);
 72:     MPI_Comm_get_attr(MPI_COMM_WORLD,MPI_TAG_UB,&maxval,&flg);
 73:     if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_LIB,"MPI error: MPI_Comm_get_attr() is not returning a MPI_TAG_UB");
 74:     counter->tag = *maxval - 128; /* hope that any still active tags were issued right at the beginning of the run */
 75:   }

 77:   *tag = counter->tag--;
 78:   if (PetscDefined(USE_DEBUG)) {
 79:     /*
 80:      Hanging here means that some processes have called PetscCommGetNewTag() and others have not.
 81:      */
 82:     MPI_Barrier(comm);
 83:   }
 84:   return(0);
 85: }

 87: /*@C
 88:   PetscCommDuplicate - Duplicates the communicator only if it is not already a PETSc communicator.

 90:   Collective

 92:   Input Parameters:
 93: . comm_in - Input communicator

 95:   Output Parameters:
 96: + comm_out - Output communicator.  May be comm_in.
 97: - first_tag - Tag available that has not already been used with this communicator (you may
 98:               pass in NULL if you do not need a tag)

100:   PETSc communicators are just regular MPI communicators that keep track of which
101:   tags have been used to prevent tag conflict. If you pass a non-PETSc communicator into
102:   a PETSc creation routine it will attach a private communicator for use in the objects communications.
103:   The internal MPI_Comm is used to perform all the MPI calls for PETSc, the outer MPI_Comm is a user
104:   level MPI_Comm that may be performing communication for the user or other library and so IS NOT used by PETSc.

106:   Level: developer

108: .seealso: PetscObjectGetNewTag(), PetscCommGetNewTag(), PetscCommDestroy()
109: @*/
110: PetscErrorCode  PetscCommDuplicate(MPI_Comm comm_in,MPI_Comm *comm_out,PetscMPIInt *first_tag)
111: {
112:   PetscErrorCode   ierr;
113:   PetscCommCounter *counter;
114:   PetscMPIInt      *maxval,flg;

117:   PetscSpinlockLock(&PetscCommSpinLock);
118:   MPI_Comm_get_attr(comm_in,Petsc_Counter_keyval,&counter,&flg);

120:   if (!flg) {  /* this is NOT a PETSc comm */
121:     union {MPI_Comm comm; void *ptr;} ucomm;
122:     /* check if this communicator has a PETSc communicator imbedded in it */
123:     MPI_Comm_get_attr(comm_in,Petsc_InnerComm_keyval,&ucomm,&flg);
124:     if (!flg) {
125:       /* This communicator is not yet known to this system, so we duplicate it and make an internal communicator */
126:       MPI_Comm_dup(comm_in,comm_out);
127:       MPI_Comm_get_attr(MPI_COMM_WORLD,MPI_TAG_UB,&maxval,&flg);
128:       if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_LIB,"MPI error: MPI_Comm_get_attr() is not returning a MPI_TAG_UB");
129:       PetscNew(&counter); /* all fields of counter are zero'ed */
130:       counter->tag = *maxval;
131:       MPI_Comm_set_attr(*comm_out,Petsc_Counter_keyval,counter);
132:       PetscInfo3(NULL,"Duplicating a communicator %ld %ld max tags = %d\n",(long)comm_in,(long)*comm_out,*maxval);

134:       /* save PETSc communicator inside user communicator, so we can get it next time */
135:       ucomm.comm = *comm_out;   /* ONLY the comm part of the union is significant. */
136:       MPI_Comm_set_attr(comm_in,Petsc_InnerComm_keyval,ucomm.ptr);
137:       ucomm.comm = comm_in;
138:       MPI_Comm_set_attr(*comm_out,Petsc_OuterComm_keyval,ucomm.ptr);
139:     } else {
140:       *comm_out = ucomm.comm;
141:       /* pull out the inner MPI_Comm and hand it back to the caller */
142:       MPI_Comm_get_attr(*comm_out,Petsc_Counter_keyval,&counter,&flg);
143:       if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Inner PETSc communicator does not have its tag/name counter attribute set");
144:       PetscInfo2(NULL,"Using internal PETSc communicator %ld %ld\n",(long)comm_in,(long)*comm_out);
145:     }
146:   } else *comm_out = comm_in;

148:   if (PetscDefined(USE_DEBUG)) {
149:     /*
150:      Hanging here means that some processes have called PetscCommDuplicate() and others have not.
151:      This likley means that a subset of processes in a MPI_Comm have attempted to create a PetscObject!
152:      ALL processes that share a communicator MUST shared objects created from that communicator.
153:      */
154:     MPI_Barrier(comm_in);
155:   }

157:   if (counter->tag < 1) {
158:     PetscInfo1(NULL,"Out of tags for object, starting to recycle. Comm reference count %d\n",counter->refcount);
159:     MPI_Comm_get_attr(MPI_COMM_WORLD,MPI_TAG_UB,&maxval,&flg);
160:     if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_LIB,"MPI error: MPI_Comm_get_attr() is not returning a MPI_TAG_UB");
161:     counter->tag = *maxval - 128; /* hope that any still active tags were issued right at the beginning of the run */
162:   }

164:   if (first_tag) *first_tag = counter->tag--;

166:   counter->refcount++; /* number of references to this comm */
167:   PetscSpinlockUnlock(&PetscCommSpinLock);
168:   return(0);
169: }

171: /*@C
172:    PetscCommDestroy - Frees communicator.  Use in conjunction with PetscCommDuplicate().

174:    Collective

176:    Input Parameter:
177: .  comm - the communicator to free

179:    Level: developer

181: .seealso:   PetscCommDuplicate()
182: @*/
183: PetscErrorCode  PetscCommDestroy(MPI_Comm *comm)
184: {
185:   PetscErrorCode   ierr;
186:   PetscCommCounter *counter;
187:   PetscMPIInt      flg;
188:   MPI_Comm         icomm = *comm,ocomm;
189:   union {MPI_Comm comm; void *ptr;} ucomm;

192:   if (*comm == MPI_COMM_NULL) return(0);
193:   PetscSpinlockLock(&PetscCommSpinLock);
194:   MPI_Comm_get_attr(icomm,Petsc_Counter_keyval,&counter,&flg);
195:   if (!flg) { /* not a PETSc comm, check if it has an inner comm */
196:     MPI_Comm_get_attr(icomm,Petsc_InnerComm_keyval,&ucomm,&flg);
197:     if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_CORRUPT,"MPI_Comm does not have tag/name counter nor does it have inner MPI_Comm");
198:     icomm = ucomm.comm;
199:     MPI_Comm_get_attr(icomm,Petsc_Counter_keyval,&counter,&flg);
200:     if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_CORRUPT,"Inner MPI_Comm does not have expected tag/name counter, problem with corrupted memory");
201:   }

203:   counter->refcount--;

205:   if (!counter->refcount) {
206:     /* if MPI_Comm has outer comm then remove reference to inner MPI_Comm from outer MPI_Comm */
207:     MPI_Comm_get_attr(icomm,Petsc_OuterComm_keyval,&ucomm,&flg);
208:     if (flg) {
209:       ocomm = ucomm.comm;
210:       MPI_Comm_get_attr(ocomm,Petsc_InnerComm_keyval,&ucomm,&flg);
211:       if (flg) {
212:         MPI_Comm_delete_attr(ocomm,Petsc_InnerComm_keyval);
213:       } else SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_CORRUPT,"Outer MPI_Comm %ld does not have expected reference to inner comm %d, problem with corrupted memory",(long int)ocomm,(long int)icomm);
214:     }

216:     PetscInfo1(NULL,"Deleting PETSc MPI_Comm %ld\n",(long)icomm);
217:     MPI_Comm_free(&icomm);
218:   }
219:   *comm = MPI_COMM_NULL;
220:   PetscSpinlockUnlock(&PetscCommSpinLock);
221:   return(0);
222: }

224: /*@C
225:     PetscObjectsListGetGlobalNumbering - computes a global numbering
226:     of PetscObjects living on subcommunicators of a given communicator.


229:     Collective.

231:     Input Parameters:
232: +   comm    - MPI_Comm
233: .   len     - local length of objlist
234: -   objlist - a list of PETSc objects living on subcomms of comm and containing this comm rank
235:               (subcomm ordering is assumed to be deadlock-free)

237:     Output Parameters:
238: +   count      - global number of distinct subcommunicators on objlist (may be > len)
239: -   numbering  - global numbers of objlist entries (allocated by user)


242:     Level: developer

244: @*/
245: PetscErrorCode  PetscObjectsListGetGlobalNumbering(MPI_Comm comm, PetscInt len, PetscObject *objlist, PetscInt *count, PetscInt *numbering)
246: {
248:   PetscInt       i, roots, offset;
249:   PetscMPIInt    size, rank;

253:   if (!count && !numbering) return(0);

255:   MPI_Comm_size(comm, &size);
256:   MPI_Comm_rank(comm, &rank);
257:   roots = 0;
258:   for (i = 0; i < len; ++i) {
259:     PetscMPIInt srank;
260:     MPI_Comm_rank(objlist[i]->comm, &srank);
261:     /* Am I the root of the i-th subcomm? */
262:     if (!srank) ++roots;
263:   }
264:   if (count) {
265:     /* Obtain the sum of all roots -- the global number of distinct subcomms. */
266:     MPIU_Allreduce(&roots,count,1,MPIU_INT,MPI_SUM,comm);
267:   }
268:   if (numbering){
269:     /* Introduce a global numbering for subcomms, initially known only by subcomm roots. */
270:     /*
271:       At each subcomm root number all of the subcomms it owns locally
272:       and make it global by calculating the shift among all of the roots.
273:       The roots are ordered using the comm ordering.
274:     */
275:     MPI_Scan(&roots,&offset,1,MPIU_INT,MPI_SUM,comm);
276:     offset -= roots;
277:     /* Now we are ready to broadcast global subcomm numbers within each subcomm.*/
278:     /*
279:       This is where the assumption of a deadlock-free ordering of the subcomms is assumed:
280:       broadcast is collective on the subcomm.
281:     */
282:     roots = 0;
283:     for (i = 0; i < len; ++i) {
284:       PetscMPIInt srank;
285:       numbering[i] = offset + roots; /* only meaningful if !srank. */

287:       MPI_Comm_rank(objlist[i]->comm, &srank);
288:       MPI_Bcast(numbering+i,1,MPIU_INT,0,objlist[i]->comm);
289:       if (!srank) ++roots;
290:     }
291:   }
292:   return(0);
293: }