Actual source code: isdiff.c
petsc-3.9.4 2018-09-11
2: #include <petsc/private/isimpl.h>
3: #include <petscbt.h>
5: /*@
6: ISDifference - Computes the difference between two index sets.
8: Collective on IS
10: Input Parameter:
11: + is1 - first index, to have items removed from it
12: - is2 - index values to be removed
14: Output Parameters:
15: . isout - is1 - is2
17: Notes:
18: Negative values are removed from the lists. is2 may have values
19: that are not in is1. This requires O(imax-imin) memory and O(imax-imin)
20: work, where imin and imax are the bounds on the indices in is1.
22: Level: intermediate
24: Concepts: index sets^difference
25: Concepts: IS^difference
27: .seealso: ISDestroy(), ISView(), ISSum(), ISExpand()
29: @*/
30: PetscErrorCode ISDifference(IS is1,IS is2,IS *isout)
31: {
33: PetscInt i,n1,n2,imin,imax,nout,*iout;
34: const PetscInt *i1,*i2;
35: PetscBT mask;
36: MPI_Comm comm;
43: ISGetIndices(is1,&i1);
44: ISGetLocalSize(is1,&n1);
46: /* Create a bit mask array to contain required values */
47: if (n1) {
48: imin = PETSC_MAX_INT;
49: imax = 0;
50: for (i=0; i<n1; i++) {
51: if (i1[i] < 0) continue;
52: imin = PetscMin(imin,i1[i]);
53: imax = PetscMax(imax,i1[i]);
54: }
55: } else imin = imax = 0;
57: PetscBTCreate(imax-imin,&mask);
58: /* Put the values from is1 */
59: for (i=0; i<n1; i++) {
60: if (i1[i] < 0) continue;
61: PetscBTSet(mask,i1[i] - imin);
62: }
63: ISRestoreIndices(is1,&i1);
64: /* Remove the values from is2 */
65: ISGetIndices(is2,&i2);
66: ISGetLocalSize(is2,&n2);
67: for (i=0; i<n2; i++) {
68: if (i2[i] < imin || i2[i] > imax) continue;
69: PetscBTClear(mask,i2[i] - imin);
70: }
71: ISRestoreIndices(is2,&i2);
73: /* Count the number in the difference */
74: nout = 0;
75: for (i=0; i<imax-imin+1; i++) {
76: if (PetscBTLookup(mask,i)) nout++;
77: }
79: /* create the new IS containing the difference */
80: PetscMalloc1(nout,&iout);
81: nout = 0;
82: for (i=0; i<imax-imin+1; i++) {
83: if (PetscBTLookup(mask,i)) iout[nout++] = i + imin;
84: }
85: PetscObjectGetComm((PetscObject)is1,&comm);
86: ISCreateGeneral(comm,nout,iout,PETSC_OWN_POINTER,isout);
88: PetscBTDestroy(&mask);
89: return(0);
90: }
92: /*@
93: ISSum - Computes the sum (union) of two index sets.
95: Only sequential version (at the moment)
97: Input Parameter:
98: + is1 - index set to be extended
99: - is2 - index values to be added
101: Output Parameter:
102: . is3 - the sum; this can not be is1 or is2
104: Notes:
105: If n1 and n2 are the sizes of the sets, this takes O(n1+n2) time;
107: Both index sets need to be sorted on input.
109: Level: intermediate
111: .seealso: ISDestroy(), ISView(), ISDifference(), ISExpand()
113: Concepts: index sets^union
114: Concepts: IS^union
116: @*/
117: PetscErrorCode ISSum(IS is1,IS is2,IS *is3)
118: {
119: MPI_Comm comm;
120: PetscBool f;
121: PetscMPIInt size;
122: const PetscInt *i1,*i2;
123: PetscInt n1,n2,n3, p1,p2, *iout;
129: PetscObjectGetComm((PetscObject)(is1),&comm);
130: MPI_Comm_size(comm,&size);
131: if (size>1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Currently only for uni-processor IS");
133: ISSorted(is1,&f);
134: if (!f) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Arg 1 is not sorted");
135: ISSorted(is2,&f);
136: if (!f) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Arg 2 is not sorted");
138: ISGetLocalSize(is1,&n1);
139: ISGetLocalSize(is2,&n2);
140: if (!n2) return(0);
141: ISGetIndices(is1,&i1);
142: ISGetIndices(is2,&i2);
144: p1 = 0; p2 = 0; n3 = 0;
145: do {
146: if (p1==n1) { /* cleanup for is2 */ n3 += n2-p2; break;
147: } else {
148: while (p2<n2 && i2[p2]<i1[p1]) {
149: n3++; p2++;
150: }
151: if (p2==n2) {
152: /* cleanup for is1 */
153: n3 += n1-p1; break;
154: } else {
155: if (i2[p2]==i1[p1]) { n3++; p1++; p2++; }
156: }
157: }
158: if (p2==n2) {
159: /* cleanup for is1 */
160: n3 += n1-p1; break;
161: } else {
162: while (p1<n1 && i1[p1]<i2[p2]) {
163: n3++; p1++;
164: }
165: if (p1==n1) {
166: /* clean up for is2 */
167: n3 += n2-p2; break;
168: } else {
169: if (i1[p1]==i2[p2]) { n3++; p1++; p2++; }
170: }
171: }
172: } while (p1<n1 || p2<n2);
174: if (n3==n1) { /* no new elements to be added */
175: ISRestoreIndices(is1,&i1);
176: ISRestoreIndices(is2,&i2);
177: ISDuplicate(is1,is3);
178: return(0);
179: }
180: PetscMalloc1(n3,&iout);
182: p1 = 0; p2 = 0; n3 = 0;
183: do {
184: if (p1==n1) { /* cleanup for is2 */
185: while (p2<n2) iout[n3++] = i2[p2++];
186: break;
187: } else {
188: while (p2<n2 && i2[p2]<i1[p1]) iout[n3++] = i2[p2++];
189: if (p2==n2) { /* cleanup for is1 */
190: while (p1<n1) iout[n3++] = i1[p1++];
191: break;
192: } else {
193: if (i2[p2]==i1[p1]) { iout[n3++] = i1[p1++]; p2++; }
194: }
195: }
196: if (p2==n2) { /* cleanup for is1 */
197: while (p1<n1) iout[n3++] = i1[p1++];
198: break;
199: } else {
200: while (p1<n1 && i1[p1]<i2[p2]) iout[n3++] = i1[p1++];
201: if (p1==n1) { /* clean up for is2 */
202: while (p2<n2) iout[n3++] = i2[p2++];
203: break;
204: } else {
205: if (i1[p1]==i2[p2]) { iout[n3++] = i1[p1++]; p2++; }
206: }
207: }
208: } while (p1<n1 || p2<n2);
210: ISRestoreIndices(is1,&i1);
211: ISRestoreIndices(is2,&i2);
212: ISCreateGeneral(comm,n3,iout,PETSC_OWN_POINTER,is3);
213: return(0);
214: }
216: /*@
217: ISExpand - Computes the union of two index sets, by concatenating 2 lists and
218: removing duplicates.
220: Collective on IS
222: Input Parameter:
223: + is1 - first index set
224: - is2 - index values to be added
226: Output Parameters:
227: . isout - is1 + is2 The index set is2 is appended to is1 removing duplicates
229: Notes:
230: Negative values are removed from the lists. This requires O(imax-imin)
231: memory and O(imax-imin) work, where imin and imax are the bounds on the
232: indices in is1 and is2.
234: The IS's do not need to be sorted.
236: Level: intermediate
238: .seealso: ISDestroy(), ISView(), ISDifference(), ISSum()
240: Concepts: index sets^difference
241: Concepts: IS^difference
243: @*/
244: PetscErrorCode ISExpand(IS is1,IS is2,IS *isout)
245: {
247: PetscInt i,n1,n2,imin,imax,nout,*iout;
248: const PetscInt *i1,*i2;
249: PetscBT mask;
250: MPI_Comm comm;
257: ISGetIndices(is1,&i1);
258: ISGetLocalSize(is1,&n1);
259: ISGetIndices(is2,&i2);
260: ISGetLocalSize(is2,&n2);
262: /* Create a bit mask array to contain required values */
263: if (n1 || n2) {
264: imin = PETSC_MAX_INT;
265: imax = 0;
266: for (i=0; i<n1; i++) {
267: if (i1[i] < 0) continue;
268: imin = PetscMin(imin,i1[i]);
269: imax = PetscMax(imax,i1[i]);
270: }
271: for (i=0; i<n2; i++) {
272: if (i2[i] < 0) continue;
273: imin = PetscMin(imin,i2[i]);
274: imax = PetscMax(imax,i2[i]);
275: }
276: } else imin = imax = 0;
278: PetscMalloc1(n1+n2,&iout);
279: nout = 0;
280: PetscBTCreate(imax-imin,&mask);
281: /* Put the values from is1 */
282: for (i=0; i<n1; i++) {
283: if (i1[i] < 0) continue;
284: if (!PetscBTLookupSet(mask,i1[i] - imin)) iout[nout++] = i1[i];
285: }
286: ISRestoreIndices(is1,&i1);
287: /* Put the values from is2 */
288: for (i=0; i<n2; i++) {
289: if (i2[i] < 0) continue;
290: if (!PetscBTLookupSet(mask,i2[i] - imin)) iout[nout++] = i2[i];
291: }
292: ISRestoreIndices(is2,&i2);
294: /* create the new IS containing the sum */
295: PetscObjectGetComm((PetscObject)is1,&comm);
296: ISCreateGeneral(comm,nout,iout,PETSC_OWN_POINTER,isout);
298: PetscBTDestroy(&mask);
299: return(0);
300: }
302: /*@
303: ISIntersect - Computes the union of two index sets, by concatenating 2 lists, sorting,
304: and finding duplicates.
306: Collective on IS
308: Input Parameter:
309: + is1 - first index set
310: - is2 - second index set
312: Output Parameters:
313: . isout - the sorted intersection of is1 and is2
315: Notes:
316: Negative values are removed from the lists. This requires O(min(is1,is2))
317: memory and O(max(is1,is2)log(max(is1,is2))) work
319: The IS's do not need to be sorted.
321: Level: intermediate
323: .seealso: ISDestroy(), ISView(), ISDifference(), ISSum(), ISExpand()
325: Concepts: index sets^intersection
326: Concepts: IS^intersection
328: @*/
329: PetscErrorCode ISIntersect(IS is1,IS is2,IS *isout)
330: {
332: PetscInt i,n1,n2,nout,*iout;
333: const PetscInt *i1,*i2;
334: IS is1sorted = NULL, is2sorted = NULL;
335: PetscBool sorted;
336: MPI_Comm comm;
343: ISGetLocalSize(is1,&n1);
344: ISGetLocalSize(is2,&n2);
345: if (n1 < n2) {
346: IS tempis = is1;
347: int ntemp = n1;
349: is1 = is2;
350: is2 = tempis;
351: n1 = n2;
352: n2 = ntemp;
353: }
354: ISSorted(is1,&sorted);
355: if (!sorted) {
356: ISDuplicate(is1,&is1sorted);
357: ISSort(is1sorted);
358: ISGetIndices(is1sorted,&i1);
359: } else {
360: is1sorted = is1;
361: PetscObjectReference((PetscObject)is1);
362: ISGetIndices(is1,&i1);
363: }
364: ISSorted(is2,&sorted);
365: if (!sorted) {
366: ISDuplicate(is2,&is2sorted);
367: ISSort(is2sorted);
368: ISGetIndices(is2sorted,&i2);
369: } else {
370: is2sorted = is2;
371: PetscObjectReference((PetscObject)is2);
372: ISGetIndices(is2,&i2);
373: }
375: PetscMalloc1(n2,&iout);
377: for (i = 0, nout = 0; i < n2; i++) {
378: PetscInt key = i2[i];
379: PetscInt loc;
381: ISLocate(is1sorted,key,&loc);
382: if (loc >= 0) {
383: if (!nout || iout[nout-1] < key) {
384: iout[nout++] = key;
385: }
386: }
387: }
388: PetscRealloc(sizeof (PetscInt) * (size_t) nout,&iout);
390: /* create the new IS containing the sum */
391: PetscObjectGetComm((PetscObject)is1,&comm);
392: ISCreateGeneral(comm,nout,iout,PETSC_OWN_POINTER,isout);
394: ISRestoreIndices(is2sorted,&i2);
395: ISDestroy(&is2sorted);
396: ISRestoreIndices(is1sorted,&i1);
397: ISDestroy(&is1sorted);
398: return(0);
399: }
401: /*@
402: ISConcatenate - Forms a new IS by locally concatenating the indices from an IS list without reordering.
405: Collective on comm.
407: Input Parameter:
408: + comm - communicator of the concatenated IS.
409: . len - size of islist array (nonnegative)
410: - islist - array of index sets
414: Output Parameters:
415: . isout - The concatenated index set; empty, if len == 0.
417: Notes: The semantics of calling this on comm imply that the comms of the members if islist also contain this rank.
419: Level: intermediate
421: .seealso: ISDifference(), ISSum(), ISExpand()
423: Concepts: index sets^concatenation
424: Concepts: IS^concatenation
426: @*/
427: PetscErrorCode ISConcatenate(MPI_Comm comm, PetscInt len, const IS islist[], IS *isout)
428: {
430: PetscInt i,n,N;
431: const PetscInt *iidx;
432: PetscInt *idx;
436: #if defined(PETSC_USE_DEBUG)
438: #endif
440: if (!len) {
441: ISCreateStride(comm, 0,0,0, isout);
442: return(0);
443: }
444: if (len < 0) SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Negative array length: %D", len);
445: N = 0;
446: for (i = 0; i < len; ++i) {
447: ISGetLocalSize(islist[i], &n);
448: N += n;
449: }
450: PetscMalloc1(N, &idx);
451: N = 0;
452: for (i = 0; i < len; ++i) {
453: ISGetLocalSize(islist[i], &n);
454: ISGetIndices(islist[i], &iidx);
455: PetscMemcpy(idx+N,iidx, sizeof(PetscInt)*n);
456: ISRestoreIndices(islist[i], &iidx);
457: N += n;
458: }
459: ISCreateGeneral(comm, N, idx, PETSC_OWN_POINTER, isout);
460: return(0);
461: }
463: /*@
464: ISListToPair - convert an IS list to a pair of ISs of equal length defining an equivalent integer multimap.
465: Each IS on the input list is assigned an integer j so that all of the indices of that IS are
466: mapped to j.
469: Collective on comm.
471: Input arguments:
472: + comm - MPI_Comm
473: . listlen - IS list length
474: - islist - IS list
476: Output arguments:
477: + xis - domain IS
478: - yis - range IS
480: Level: advanced
482: Notes:
483: The global integers assigned to the ISs of the local input list might not correspond to the
484: local numbers of the ISs on that list, but the two *orderings* are the same: the global
485: integers assigned to the ISs on the local list form a strictly increasing sequence.
487: The ISs on the input list can belong to subcommunicators of comm, and the subcommunicators
488: on the input IS list are assumed to be in a "deadlock-free" order.
490: Local lists of PetscObjects (or their subcommes) on a comm are "deadlock-free" if subcomm1
491: preceeds subcomm2 on any local list, then it preceeds subcomm2 on all ranks.
492: Equivalently, the local numbers of the subcomms on each local list are drawn from some global
493: numbering. This is ensured, for example, by ISPairToList().
495: .seealso ISPairToList()
496: @*/
497: PetscErrorCode ISListToPair(MPI_Comm comm, PetscInt listlen, IS islist[], IS *xis, IS *yis)
498: {
500: PetscInt ncolors, *colors,i, leni,len,*xinds, *yinds,k,j;
501: const PetscInt *indsi;
504: PetscMalloc1(listlen, &colors);
505: PetscObjectsListGetGlobalNumbering(comm, listlen, (PetscObject*)islist,&ncolors, colors);
506: len = 0;
507: for (i = 0; i < listlen; ++i) {
508: ISGetLocalSize(islist[i], &leni);
509: len += leni;
510: }
511: PetscMalloc1(len, &xinds);
512: PetscMalloc1(len, &yinds);
513: k = 0;
514: for (i = 0; i < listlen; ++i) {
515: ISGetLocalSize(islist[i], &leni);
516: ISGetIndices(islist[i],&indsi);
517: for (j = 0; j < leni; ++j) {
518: xinds[k] = indsi[j];
519: yinds[k] = colors[i];
520: ++k;
521: }
522: }
523: PetscFree(colors);
524: ISCreateGeneral(comm,len,xinds,PETSC_OWN_POINTER,xis);
525: ISCreateGeneral(comm,len,yinds,PETSC_OWN_POINTER,yis);
526: return(0);
527: }
530: /*@
531: ISPairToList - convert an IS pair encoding an integer map to a list of ISs.
532: Each IS on the output list contains the preimage for each index on the second input IS.
533: The ISs on the output list are constructed on the subcommunicators of the input IS pair.
534: Each subcommunicator corresponds to the preimage of some index j -- this subcomm contains
535: exactly the ranks that assign some indices i to j. This is essentially the inverse of
536: ISListToPair().
538: Collective on indis.
540: Input arguments:
541: + xis - domain IS
542: - yis - range IS
544: Output arguments:
545: + listlen - length of islist
546: - islist - list of ISs breaking up indis by color
548: Note:
549: + xis and yis must be of the same length and have congruent communicators.
550: - The resulting ISs have subcommunicators in a "deadlock-free" order (see ISListToPair()).
552: Level: advanced
554: .seealso ISListToPair()
555: @*/
556: PetscErrorCode ISPairToList(IS xis, IS yis, PetscInt *listlen, IS **islist)
557: {
559: IS indis = xis, coloris = yis;
560: PetscInt *inds, *colors, llen, ilen, lstart, lend, lcount,l;
561: PetscMPIInt rank, size, llow, lhigh, low, high,color,subsize;
562: const PetscInt *ccolors, *cinds;
563: MPI_Comm comm, subcomm;
571: PetscObjectGetComm((PetscObject)xis,&comm);
572: MPI_Comm_rank(comm, &rank);
573: MPI_Comm_rank(comm, &size);
574: /* Extract, copy and sort the local indices and colors on the color. */
575: ISGetLocalSize(coloris, &llen);
576: ISGetLocalSize(indis, &ilen);
577: if (llen != ilen) SETERRQ2(comm, PETSC_ERR_ARG_SIZ, "Incompatible IS sizes: %D and %D", ilen, llen);
578: ISGetIndices(coloris, &ccolors);
579: ISGetIndices(indis, &cinds);
580: PetscMalloc2(ilen,&inds,llen,&colors);
581: PetscMemcpy(inds,cinds,ilen*sizeof(PetscInt));
582: PetscMemcpy(colors,ccolors,llen*sizeof(PetscInt));
583: PetscSortIntWithArray(llen, colors, inds);
584: /* Determine the global extent of colors. */
585: llow = 0; lhigh = -1;
586: lstart = 0; lcount = 0;
587: while (lstart < llen) {
588: lend = lstart+1;
589: while (lend < llen && colors[lend] == colors[lstart]) ++lend;
590: llow = PetscMin(llow,colors[lstart]);
591: lhigh = PetscMax(lhigh,colors[lstart]);
592: ++lcount;
593: }
594: MPIU_Allreduce(&llow,&low,1,MPI_INT,MPI_MIN,comm);
595: MPIU_Allreduce(&lhigh,&high,1,MPI_INT,MPI_MAX,comm);
596: *listlen = 0;
597: if (low <= high) {
598: if (lcount > 0) {
599: *listlen = lcount;
600: if (!*islist) {
601: PetscMalloc1(lcount, islist);
602: }
603: }
604: /*
605: Traverse all possible global colors, and participate in the subcommunicators
606: for the locally-supported colors.
607: */
608: lcount = 0;
609: lstart = 0; lend = 0;
610: for (l = low; l <= high; ++l) {
611: /*
612: Find the range of indices with the same color, which is not smaller than l.
613: Observe that, since colors is sorted, and is a subsequence of [low,high],
614: as soon as we find a new color, it is >= l.
615: */
616: if (lstart < llen) {
617: /* The start of the next locally-owned color is identified. Now look for the end. */
618: if (lstart == lend) {
619: lend = lstart+1;
620: while (lend < llen && colors[lend] == colors[lstart]) ++lend;
621: }
622: /* Now check whether the identified color segment matches l. */
623: if (colors[lstart] < l) SETERRQ3(PETSC_COMM_SELF, PETSC_ERR_PLIB, "Locally owned color %D at location %D is < than the next global color %D", colors[lstart], lcount, l);
624: }
625: color = (PetscMPIInt)(colors[lstart] == l);
626: /* Check whether a proper subcommunicator exists. */
627: MPIU_Allreduce(&color,&subsize,1,MPI_INT,MPI_SUM,comm);
629: if (subsize == 1) subcomm = PETSC_COMM_SELF;
630: else if (subsize == size) subcomm = comm;
631: else {
632: /* a proper communicator is necessary, so we create it. */
633: MPI_Comm_split(comm, color, rank, &subcomm);
634: }
635: if (colors[lstart] == l) {
636: /* If we have l among the local colors, we create an IS to hold the corresponding indices. */
637: ISCreateGeneral(subcomm, lend-lstart,inds+lstart,PETSC_COPY_VALUES,*islist+lcount);
638: /* Position lstart at the beginning of the next local color. */
639: lstart = lend;
640: /* Increment the counter of the local colors split off into an IS. */
641: ++lcount;
642: }
643: if (subsize > 0 && subsize < size) {
644: /*
645: Irrespective of color, destroy the split off subcomm:
646: a subcomm used in the IS creation above is duplicated
647: into a proper PETSc comm.
648: */
649: MPI_Comm_free(&subcomm);
650: }
651: } /* for (l = low; l < high; ++l) */
652: } /* if (low <= high) */
653: PetscFree2(inds,colors);
654: return(0);
655: }
658: /*@
659: ISEmbed - embed IS a into IS b by finding the locations in b that have the same indices as in a.
660: If c is the IS of these locations, we have a = b*c, regarded as a composition of the
661: corresponding ISLocalToGlobalMaps.
663: Not collective.
665: Input arguments:
666: + a - IS to embed
667: . b - IS to embed into
668: - drop - flag indicating whether to drop a's indices that are not in b.
670: Output arguments:
671: . c - local embedding indices
673: Note:
674: If some of a's global indices are not among b's indices the embedding is impossible. The local indices of a
675: corresponding to these global indices are either mapped to -1 (if !drop) or are omitted (if drop). In the former
676: case the size of c is that same as that of a, in the latter case c's size may be smaller.
678: The resulting IS is sequential, since the index substition it encodes is purely local.
680: Level: advanced
682: .seealso ISLocalToGlobalMapping
683: @*/
684: PetscErrorCode ISEmbed(IS a, IS b, PetscBool drop, IS *c)
685: {
686: PetscErrorCode ierr;
687: ISLocalToGlobalMapping ltog;
688: ISGlobalToLocalMappingMode gtoltype = IS_GTOLM_DROP;
689: PetscInt alen, clen, *cindices, *cindices2;
690: const PetscInt *aindices;
696: ISLocalToGlobalMappingCreateIS(b, <og);
697: ISGetLocalSize(a, &alen);
698: ISGetIndices(a, &aindices);
699: PetscMalloc1(alen, &cindices);
700: if (!drop) gtoltype = IS_GTOLM_MASK;
701: ISGlobalToLocalMappingApply(ltog,gtoltype,alen,aindices,&clen,cindices);
702: ISLocalToGlobalMappingDestroy(<og);
703: if (clen != alen) {
704: cindices2 = cindices;
705: PetscMalloc1(clen, &cindices);
706: PetscMemcpy(cindices,cindices2,clen*sizeof(PetscInt));
707: PetscFree(cindices2);
708: }
709: ISCreateGeneral(PETSC_COMM_SELF,clen,cindices,PETSC_OWN_POINTER,c);
710: return(0);
711: }
714: /*@
715: ISSortPermutation - calculate the permutation of the indices into a nondecreasing order.
717: Not collective.
719: Input arguments:
720: + f - IS to sort
721: - always - build the permutation even when f's indices are nondecreasin.
723: Output argument:
724: . h - permutation or NULL, if f is nondecreasing and always == PETSC_TRUE.
727: Note: Indices in f are unchanged. f[h[i]] is the i-th smallest f index.
728: If always == PETSC_FALSE, an extra check is peformed to see whether
729: the f indices are nondecreasing. h is built on PETSC_COMM_SELF, since
730: the permutation has a local meaning only.
732: Level: advanced
734: .seealso ISLocalToGlobalMapping, ISSort(), PetscIntSortWithPermutation()
735: @*/
736: PetscErrorCode ISSortPermutation(IS f,PetscBool always,IS *h)
737: {
738: PetscErrorCode ierr;
739: const PetscInt *findices;
740: PetscInt fsize,*hindices,i;
741: PetscBool isincreasing;
746: ISGetLocalSize(f,&fsize);
747: ISGetIndices(f,&findices);
748: *h = NULL;
749: if (!always) {
750: isincreasing = PETSC_TRUE;
751: for (i = 1; i < fsize; ++i) {
752: if (findices[i] <= findices[i-1]) {
753: isincreasing = PETSC_FALSE;
754: break;
755: }
756: }
757: if (isincreasing) {
758: ISRestoreIndices(f,&findices);
759: return(0);
760: }
761: }
762: PetscMalloc1(fsize,&hindices);
763: for (i = 0; i < fsize; ++i) hindices[i] = i;
764: PetscSortIntWithPermutation(fsize,findices,hindices);
765: ISRestoreIndices(f,&findices);
766: ISCreateGeneral(PETSC_COMM_SELF,fsize,hindices,PETSC_OWN_POINTER,h);
767: return(0);
768: }