Actual source code: tagm.c
1: #include <petsc/private/petscimpl.h>
2: #include <petsc/private/hashmapobj.h>
3: #include <petsc/private/garbagecollector.h>
5: /*
6: A simple way to manage tags inside a communicator.
8: It uses the attributes to determine if a new communicator
9: is needed and to store the available tags.
11: */
13: /*@C
14: PetscObjectGetNewTag - Gets a unique new tag from a PETSc object. All
15: processors that share the object MUST call this routine EXACTLY the same
16: number of times. This tag should only be used with the current objects
17: communicator; do NOT use it with any other MPI communicator.
19: Collective
21: Input Parameter:
22: . obj - the PETSc object; this must be cast with a (`PetscObject`), for example,
23: `PetscObjectGetNewTag`((`PetscObject`)mat,&tag);
25: Output Parameter:
26: . tag - the new tag
28: Level: developer
30: Note:
31: This tag is needed if one is writing MPI communication code involving message passing and needs unique MPI tags to ensure the messages are connected to this specific
32: object.
34: .seealso: `PetscCommGetNewTag()`
35: @*/
36: PetscErrorCode PetscObjectGetNewTag(PetscObject obj, PetscMPIInt *tag)
37: {
38: PetscFunctionBegin;
39: PetscCall(PetscCommGetNewTag(obj->comm, tag));
40: PetscFunctionReturn(PETSC_SUCCESS);
41: }
43: /*@
44: PetscCommGetNewTag - Gets a unique new tag from a PETSc communicator
46: Collective
48: Input Parameter:
49: . comm - the MPI communicator
51: Output Parameter:
52: . tag - the new tag
54: Level: developer
56: Notes:
57: All processors that share the communicator MUST call this routine EXACTLY the same number of
58: times. This tag should only be used with the current objects communicator; do NOT use it
59: with any other MPI communicator.
61: .seealso: `PetscObjectGetNewTag()`, `PetscCommDuplicate()`
62: @*/
63: PetscErrorCode PetscCommGetNewTag(MPI_Comm comm, PetscMPIInt *tag)
64: {
65: PetscCommCounter *counter;
66: PetscMPIInt *maxval, flg;
68: PetscFunctionBegin;
69: PetscAssertPointer(tag, 2);
71: PetscCallMPI(MPI_Comm_get_attr(comm, Petsc_Counter_keyval, &counter, &flg));
72: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_CORRUPT, "Bad MPI communicator supplied; must be a PETSc communicator");
74: if (counter->tag < 1) {
75: PetscCall(PetscInfo(NULL, "Out of tags for object, starting to recycle. Comm reference count %" PetscInt_FMT "\n", counter->refcount));
76: PetscCallMPI(MPI_Comm_get_attr(MPI_COMM_WORLD, MPI_TAG_UB, &maxval, &flg));
77: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_LIB, "MPI error: MPI_Comm_get_attr() is not returning a MPI_TAG_UB");
78: counter->tag = *maxval - 128; /* hope that any still active tags were issued right at the beginning of the run */
79: }
81: *tag = counter->tag--;
82: if (PetscDefined(USE_DEBUG)) {
83: /*
84: Hanging here means that some processes have called PetscCommGetNewTag() and others have not.
85: */
86: PetscCallMPI(MPI_Barrier(comm));
87: }
88: PetscFunctionReturn(PETSC_SUCCESS);
89: }
91: /*@C
92: PetscCommGetComm - get a new MPI communicator from a PETSc communicator that can be passed off to another package
94: Collective
96: Input Parameter:
97: . comm_in - Input communicator
99: Output Parameter:
100: . comm_out - Output communicator
102: Level: developer
104: Notes:
105: Use `PetscCommRestoreComm()` to return the communicator when the external package no longer needs it
107: Certain MPI implementations have `MPI_Comm_free()` that do not work, thus one can run out of available MPI communicators causing
108: mysterious crashes in the code after running a long time. This routine allows reusing previously obtained MPI communicators that
109: are no longer needed.
111: .seealso: `PetscObjectGetNewTag()`, `PetscCommGetNewTag()`, `PetscCommDestroy()`, `PetscCommRestoreComm()`
112: @*/
113: PetscErrorCode PetscCommGetComm(MPI_Comm comm_in, MPI_Comm *comm_out)
114: {
115: PetscCommCounter *counter;
116: PetscMPIInt flg;
118: PetscFunctionBegin;
119: PetscCall(PetscSpinlockLock(&PetscCommSpinLock));
120: PetscCallMPI(MPI_Comm_get_attr(comm_in, Petsc_Counter_keyval, &counter, &flg));
121: PetscCheck(flg, comm_in, PETSC_ERR_ARG_WRONGSTATE, "Requires a PETSc communicator as input, do not use something like MPI_COMM_WORLD");
123: if (counter->comms) {
124: struct PetscCommStash *pcomms = counter->comms;
126: *comm_out = pcomms->comm;
127: counter->comms = pcomms->next;
128: PetscCall(PetscFree(pcomms));
129: PetscCall(PetscInfo(NULL, "Reusing a communicator %ld %ld\n", (long)comm_in, (long)*comm_out));
130: } else {
131: PetscCallMPI(MPI_Comm_dup(comm_in, comm_out));
132: }
133: PetscCall(PetscSpinlockUnlock(&PetscCommSpinLock));
134: PetscFunctionReturn(PETSC_SUCCESS);
135: }
137: /*@C
138: PetscCommRestoreComm - restores an MPI communicator that was obtained with `PetscCommGetComm()`
140: Collective
142: Input Parameters:
143: + comm_in - Input communicator
144: - comm_out - returned communicator
146: Level: developer
148: .seealso: `PetscObjectGetNewTag()`, `PetscCommGetNewTag()`, `PetscCommDestroy()`
149: @*/
150: PetscErrorCode PetscCommRestoreComm(MPI_Comm comm_in, MPI_Comm *comm_out)
151: {
152: PetscCommCounter *counter;
153: PetscMPIInt flg;
154: struct PetscCommStash *pcomms, *ncomm;
156: PetscFunctionBegin;
157: PetscCall(PetscSpinlockLock(&PetscCommSpinLock));
158: PetscCallMPI(MPI_Comm_get_attr(comm_in, Petsc_Counter_keyval, &counter, &flg));
159: PetscCheck(flg, comm_in, PETSC_ERR_ARG_WRONGSTATE, "Requires a PETSc communicator as input, do not use something like MPI_COMM_WORLD");
161: PetscCall(PetscMalloc(sizeof(struct PetscCommStash), &ncomm));
162: ncomm->comm = *comm_out;
163: ncomm->next = NULL;
164: pcomms = counter->comms;
165: while (pcomms && pcomms->next) pcomms = pcomms->next;
166: if (pcomms) {
167: pcomms->next = ncomm;
168: } else {
169: counter->comms = ncomm;
170: }
171: *comm_out = 0;
172: PetscCall(PetscSpinlockUnlock(&PetscCommSpinLock));
173: PetscFunctionReturn(PETSC_SUCCESS);
174: }
176: /*@C
177: PetscCommDuplicate - Duplicates the communicator only if it is not already a PETSc communicator.
179: Collective
181: Input Parameter:
182: . comm_in - Input communicator
184: Output Parameters:
185: + comm_out - Output communicator. May be `comm_in`.
186: - first_tag - Tag available that has not already been used with this communicator (you may pass in `NULL` if you do not need a tag)
188: Level: developer
190: Note:
191: PETSc communicators are just regular MPI communicators that keep track of which
192: tags have been used to prevent tag conflict. If you pass a non-PETSc communicator into
193: a PETSc creation routine it will attach a private communicator for use in the objects communications.
194: The internal `MPI_Comm` is used to perform all the MPI calls for PETSc, the outer `MPI_Comm` is a user
196: `MPI_Comm` That May Be Performing Communication For The User Or Other Library And So Is Not Used By Petsc.
198: .seealso: `PetscObjectGetNewTag()`, `PetscCommGetNewTag()`, `PetscCommDestroy()`
199: @*/
200: PetscErrorCode PetscCommDuplicate(MPI_Comm comm_in, MPI_Comm *comm_out, PetscMPIInt *first_tag)
201: {
202: PetscInt64 *cidx;
203: PetscCommCounter *counter;
204: PetscMPIInt *maxval, flg;
206: PetscFunctionBegin;
207: PetscCall(PetscSpinlockLock(&PetscCommSpinLock));
208: PetscCallMPI(MPI_Comm_get_attr(comm_in, Petsc_Counter_keyval, &counter, &flg));
210: if (!flg) { /* this is NOT a PETSc comm */
211: union
212: {
213: MPI_Comm comm;
214: void *ptr;
215: } ucomm;
216: /* check if this communicator has a PETSc communicator embedded in it */
217: PetscCallMPI(MPI_Comm_get_attr(comm_in, Petsc_InnerComm_keyval, &ucomm, &flg));
218: if (!flg) {
219: /* This communicator is not yet known to this system, so we duplicate it and make an internal communicator */
220: PetscCallMPI(MPI_Comm_dup(comm_in, comm_out));
221: PetscCallMPI(MPI_Comm_get_attr(MPI_COMM_WORLD, MPI_TAG_UB, &maxval, &flg));
222: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_LIB, "MPI error: MPI_Comm_get_attr() is not returning a MPI_TAG_UB");
223: PetscCall(PetscNew(&counter)); /* all fields of counter are zero'ed */
224: counter->tag = *maxval;
225: PetscCallMPI(MPI_Comm_set_attr(*comm_out, Petsc_Counter_keyval, counter));
226: /* Add an object creation index to the communicator */
227: PetscCall(PetscNew(&cidx));
228: PetscCallMPI(MPI_Comm_set_attr(*comm_out, Petsc_CreationIdx_keyval, cidx));
229: PetscCall(PetscInfo(NULL, "Duplicating a communicator %ld %ld max tags = %d\n", (long)comm_in, (long)*comm_out, *maxval));
231: /* save PETSc communicator inside user communicator, so we can get it next time */
232: ucomm.comm = *comm_out; /* ONLY the comm part of the union is significant. */
233: PetscCallMPI(MPI_Comm_set_attr(comm_in, Petsc_InnerComm_keyval, ucomm.ptr));
234: ucomm.comm = comm_in;
235: PetscCallMPI(MPI_Comm_set_attr(*comm_out, Petsc_OuterComm_keyval, ucomm.ptr));
236: } else {
237: *comm_out = ucomm.comm;
238: /* pull out the inner MPI_Comm and hand it back to the caller */
239: PetscCallMPI(MPI_Comm_get_attr(*comm_out, Petsc_Counter_keyval, &counter, &flg));
240: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Inner PETSc communicator does not have its tag/name counter attribute set");
241: PetscCall(PetscInfo(NULL, "Using internal PETSc communicator %ld %ld\n", (long)comm_in, (long)*comm_out));
242: }
243: } else *comm_out = comm_in;
245: if (PetscDefined(USE_DEBUG)) {
246: /*
247: Hanging here means that some processes have called PetscCommDuplicate() and others have not.
248: This likely means that a subset of processes in a MPI_Comm have attempted to create a PetscObject!
249: ALL processes that share a communicator MUST shared objects created from that communicator.
250: */
251: PetscCallMPI(MPI_Barrier(comm_in));
252: }
254: if (counter->tag < 1) {
255: PetscCall(PetscInfo(NULL, "Out of tags for object, starting to recycle. Comm reference count %" PetscInt_FMT "\n", counter->refcount));
256: PetscCallMPI(MPI_Comm_get_attr(MPI_COMM_WORLD, MPI_TAG_UB, &maxval, &flg));
257: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_LIB, "MPI error: MPI_Comm_get_attr() is not returning a MPI_TAG_UB");
258: counter->tag = *maxval - 128; /* hope that any still active tags were issued right at the beginning of the run */
259: }
261: if (first_tag) *first_tag = counter->tag--;
263: counter->refcount++; /* number of references to this comm */
264: PetscCall(PetscSpinlockUnlock(&PetscCommSpinLock));
265: PetscFunctionReturn(PETSC_SUCCESS);
266: }
268: /*@C
269: PetscCommDestroy - Frees communicator obtained with `PetscCommDuplicate()`.
271: Collective
273: Input Parameter:
274: . comm - the communicator to free
276: Level: developer
278: .seealso: `PetscCommDuplicate()`
279: @*/
280: PetscErrorCode PetscCommDestroy(MPI_Comm *comm)
281: {
282: PetscInt64 *cidx;
283: PetscCommCounter *counter;
284: PetscMPIInt flg;
285: PetscGarbage garbage;
286: MPI_Comm icomm = *comm, ocomm;
287: union
288: {
289: MPI_Comm comm;
290: void *ptr;
291: } ucomm;
293: PetscFunctionBegin;
294: if (*comm == MPI_COMM_NULL) PetscFunctionReturn(PETSC_SUCCESS);
295: PetscCall(PetscSpinlockLock(&PetscCommSpinLock));
296: PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_Counter_keyval, &counter, &flg));
297: if (!flg) { /* not a PETSc comm, check if it has an inner comm */
298: PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_InnerComm_keyval, &ucomm, &flg));
299: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_CORRUPT, "MPI_Comm does not have tag/name counter nor does it have inner MPI_Comm");
300: icomm = ucomm.comm;
301: PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_Counter_keyval, &counter, &flg));
302: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_CORRUPT, "Inner MPI_Comm does not have expected tag/name counter, problem with corrupted memory");
303: }
304: counter->refcount--;
305: if (!counter->refcount) {
306: /* if MPI_Comm has outer comm then remove reference to inner MPI_Comm from outer MPI_Comm */
307: PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_OuterComm_keyval, &ucomm, &flg));
308: if (flg) {
309: ocomm = ucomm.comm;
310: PetscCallMPI(MPI_Comm_get_attr(ocomm, Petsc_InnerComm_keyval, &ucomm, &flg));
311: PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_ARG_CORRUPT, "Outer MPI_Comm %ld does not have expected reference to inner comm %ld, problem with corrupted memory", (long int)ocomm, (long int)icomm);
312: PetscCallMPI(MPI_Comm_delete_attr(ocomm, Petsc_InnerComm_keyval));
313: }
315: /* Remove the object creation index on the communicator */
316: PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_CreationIdx_keyval, &cidx, &flg));
317: if (flg) {
318: PetscCall(PetscFree(cidx));
319: } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_CORRUPT, "MPI_Comm does not have object creation index");
321: /* Remove garbage hashmap set up by garbage collection */
322: PetscCallMPI(MPI_Comm_get_attr(icomm, Petsc_Garbage_HMap_keyval, &garbage, &flg));
323: if (flg) {
324: PetscInt entries = 0;
325: PetscCall(PetscHMapObjGetSize(garbage.map, &entries));
326: if (entries > 0) PetscCall(PetscGarbageCleanup(icomm));
327: PetscCall(PetscHMapObjDestroy(&(garbage.map)));
328: }
330: PetscCall(PetscInfo(NULL, "Deleting PETSc MPI_Comm %ld\n", (long)icomm));
331: PetscCallMPI(MPI_Comm_free(&icomm));
332: }
333: *comm = MPI_COMM_NULL;
334: PetscCall(PetscSpinlockUnlock(&PetscCommSpinLock));
335: PetscFunctionReturn(PETSC_SUCCESS);
336: }
338: /*@C
339: PetscObjectsListGetGlobalNumbering - computes a global numbering
340: of `PetscObject`s living on subcommunicators of a given communicator.
342: Collective.
344: Input Parameters:
345: + comm - the `MPI_Comm`
346: . len - local length of `objlist`
347: - objlist - a list of PETSc objects living on subcomms of comm and containing this comm rank
348: (subcomm ordering is assumed to be deadlock-free)
350: Output Parameters:
351: + count - global number of distinct subcommunicators on objlist (may be > len)
352: - numbering - global numbers of objlist entries (allocated by user)
354: Level: developer
356: Note:
357: This is needed when PETSc is used with certain languages that do garbage collection to manage object life cycles.
359: .seealso: `PetscCommDuplicate()`, `PetscObjectDestroy()`
360: @*/
361: PetscErrorCode PetscObjectsListGetGlobalNumbering(MPI_Comm comm, PetscInt len, PetscObject *objlist, PetscInt *count, PetscInt *numbering)
362: {
363: PetscInt i, roots, offset;
364: PetscMPIInt size, rank;
366: PetscFunctionBegin;
367: PetscAssertPointer(objlist, 3);
368: if (!count && !numbering) PetscFunctionReturn(PETSC_SUCCESS);
370: PetscCallMPI(MPI_Comm_size(comm, &size));
371: PetscCallMPI(MPI_Comm_rank(comm, &rank));
372: roots = 0;
373: for (i = 0; i < len; ++i) {
374: PetscMPIInt srank;
375: PetscCallMPI(MPI_Comm_rank(objlist[i]->comm, &srank));
376: /* Am I the root of the i-th subcomm? */
377: if (!srank) ++roots;
378: }
379: if (count) {
380: /* Obtain the sum of all roots -- the global number of distinct subcomms. */
381: PetscCall(MPIU_Allreduce(&roots, count, 1, MPIU_INT, MPI_SUM, comm));
382: }
383: if (numbering) {
384: /* Introduce a global numbering for subcomms, initially known only by subcomm roots. */
385: /*
386: At each subcomm root number all of the subcomms it owns locally
387: and make it global by calculating the shift among all of the roots.
388: The roots are ordered using the comm ordering.
389: */
390: PetscCallMPI(MPI_Scan(&roots, &offset, 1, MPIU_INT, MPI_SUM, comm));
391: offset -= roots;
392: /* Now we are ready to broadcast global subcomm numbers within each subcomm.*/
393: /*
394: This is where the assumption of a deadlock-free ordering of the subcomms is assumed:
395: broadcast is collective on the subcomm.
396: */
397: roots = 0;
398: for (i = 0; i < len; ++i) {
399: PetscMPIInt srank;
400: numbering[i] = offset + roots; /* only meaningful if !srank. */
402: PetscCallMPI(MPI_Comm_rank(objlist[i]->comm, &srank));
403: PetscCallMPI(MPI_Bcast(numbering + i, 1, MPIU_INT, 0, objlist[i]->comm));
404: if (!srank) ++roots;
405: }
406: }
407: PetscFunctionReturn(PETSC_SUCCESS);
408: }