Date: 2021-03-03T22:25:41+00:00

Actual source code: tagm.c
petsc-3.14.5 2021-03-03
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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: }