1 2 /* 3 This file defines a "solve the problem redistributely on each subgroup of processor" preconditioner. 4 */ 5 #include <petsc/private/pcimpl.h> /*I "petscksp.h" I*/ 6 #include <petscksp.h> 7 8 typedef struct { 9 KSP ksp; 10 Vec x,b; 11 VecScatter scatter; 12 IS is; 13 PetscInt dcnt,*drows; /* these are the local rows that have only diagonal entry */ 14 PetscScalar *diag; 15 Vec work; 16 } PC_Redistribute; 17 18 static PetscErrorCode PCView_Redistribute(PC pc,PetscViewer viewer) 19 { 20 PC_Redistribute *red = (PC_Redistribute*)pc->data; 21 PetscErrorCode ierr; 22 PetscBool iascii,isstring; 23 PetscInt ncnt,N; 24 25 PetscFunctionBegin; 26 ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr); 27 ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);CHKERRQ(ierr); 28 if (iascii) { 29 ierr = MPIU_Allreduce(&red->dcnt,&ncnt,1,MPIU_INT,MPI_SUM,PetscObjectComm((PetscObject)pc));CHKERRQ(ierr); 30 ierr = MatGetSize(pc->pmat,&N,NULL);CHKERRQ(ierr); 31 ierr = PetscViewerASCIIPrintf(viewer," Number rows eliminated %D Percentage rows eliminated %g\n",ncnt,100.0*((PetscReal)ncnt)/((PetscReal)N));CHKERRQ(ierr); 32 ierr = PetscViewerASCIIPrintf(viewer," Redistribute preconditioner: \n");CHKERRQ(ierr); 33 ierr = KSPView(red->ksp,viewer);CHKERRQ(ierr); 34 } else if (isstring) { 35 ierr = PetscViewerStringSPrintf(viewer," Redistribute preconditioner");CHKERRQ(ierr); 36 ierr = KSPView(red->ksp,viewer);CHKERRQ(ierr); 37 } 38 PetscFunctionReturn(0); 39 } 40 41 static PetscErrorCode PCSetUp_Redistribute(PC pc) 42 { 43 PC_Redistribute *red = (PC_Redistribute*)pc->data; 44 PetscErrorCode ierr; 45 MPI_Comm comm; 46 PetscInt rstart,rend,i,nz,cnt,*rows,ncnt,dcnt,*drows; 47 PetscLayout map,nmap; 48 PetscMPIInt size,imdex,tag,n; 49 PetscInt *source = NULL; 50 PetscMPIInt *sizes = NULL,nrecvs; 51 PetscInt j,nsends; 52 PetscInt *owner = NULL,*starts = NULL,count,slen; 53 PetscInt *rvalues,*svalues,recvtotal; 54 PetscMPIInt *onodes1,*olengths1; 55 MPI_Request *send_waits = NULL,*recv_waits = NULL; 56 MPI_Status recv_status,*send_status; 57 Vec tvec,diag; 58 Mat tmat; 59 const PetscScalar *d; 60 61 PetscFunctionBegin; 62 if (pc->setupcalled) { 63 ierr = KSPGetOperators(red->ksp,NULL,&tmat);CHKERRQ(ierr); 64 ierr = MatCreateSubMatrix(pc->pmat,red->is,red->is,MAT_REUSE_MATRIX,&tmat);CHKERRQ(ierr); 65 ierr = KSPSetOperators(red->ksp,tmat,tmat);CHKERRQ(ierr); 66 } else { 67 PetscInt NN; 68 69 ierr = PetscObjectGetComm((PetscObject)pc,&comm);CHKERRQ(ierr); 70 ierr = MPI_Comm_size(comm,&size);CHKERRQ(ierr); 71 ierr = PetscObjectGetNewTag((PetscObject)pc,&tag);CHKERRQ(ierr); 72 73 /* count non-diagonal rows on process */ 74 ierr = MatGetOwnershipRange(pc->mat,&rstart,&rend);CHKERRQ(ierr); 75 cnt = 0; 76 for (i=rstart; i<rend; i++) { 77 ierr = MatGetRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 78 if (nz > 1) cnt++; 79 ierr = MatRestoreRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 80 } 81 ierr = PetscMalloc1(cnt,&rows);CHKERRQ(ierr); 82 ierr = PetscMalloc1(rend - rstart - cnt,&drows);CHKERRQ(ierr); 83 84 /* list non-diagonal rows on process */ 85 cnt = 0; dcnt = 0; 86 for (i=rstart; i<rend; i++) { 87 ierr = MatGetRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 88 if (nz > 1) rows[cnt++] = i; 89 else drows[dcnt++] = i - rstart; 90 ierr = MatRestoreRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 91 } 92 93 /* create PetscLayout for non-diagonal rows on each process */ 94 ierr = PetscLayoutCreate(comm,&map);CHKERRQ(ierr); 95 ierr = PetscLayoutSetLocalSize(map,cnt);CHKERRQ(ierr); 96 ierr = PetscLayoutSetBlockSize(map,1);CHKERRQ(ierr); 97 ierr = PetscLayoutSetUp(map);CHKERRQ(ierr); 98 rstart = map->rstart; 99 rend = map->rend; 100 101 /* create PetscLayout for load-balanced non-diagonal rows on each process */ 102 ierr = PetscLayoutCreate(comm,&nmap);CHKERRQ(ierr); 103 ierr = MPIU_Allreduce(&cnt,&ncnt,1,MPIU_INT,MPI_SUM,comm);CHKERRQ(ierr); 104 ierr = PetscLayoutSetSize(nmap,ncnt);CHKERRQ(ierr); 105 ierr = PetscLayoutSetBlockSize(nmap,1);CHKERRQ(ierr); 106 ierr = PetscLayoutSetUp(nmap);CHKERRQ(ierr); 107 108 ierr = MatGetSize(pc->pmat,&NN,NULL);CHKERRQ(ierr); 109 ierr = PetscInfo2(pc,"Number of diagonal rows eliminated %d, percentage eliminated %g\n",NN-ncnt,((PetscReal)(NN-ncnt))/((PetscReal)(NN)));CHKERRQ(ierr); 110 /* 111 this code is taken from VecScatterCreate_PtoS() 112 Determines what rows need to be moved where to 113 load balance the non-diagonal rows 114 */ 115 /* count number of contributors to each processor */ 116 ierr = PetscMalloc2(size,&sizes,cnt,&owner);CHKERRQ(ierr); 117 ierr = PetscArrayzero(sizes,size);CHKERRQ(ierr); 118 j = 0; 119 nsends = 0; 120 for (i=rstart; i<rend; i++) { 121 if (i < nmap->range[j]) j = 0; 122 for (; j<size; j++) { 123 if (i < nmap->range[j+1]) { 124 if (!sizes[j]++) nsends++; 125 owner[i-rstart] = j; 126 break; 127 } 128 } 129 } 130 /* inform other processors of number of messages and max length*/ 131 ierr = PetscGatherNumberOfMessages(comm,NULL,sizes,&nrecvs);CHKERRQ(ierr); 132 ierr = PetscGatherMessageLengths(comm,nsends,nrecvs,sizes,&onodes1,&olengths1);CHKERRQ(ierr); 133 ierr = PetscSortMPIIntWithArray(nrecvs,onodes1,olengths1);CHKERRQ(ierr); 134 recvtotal = 0; for (i=0; i<nrecvs; i++) recvtotal += olengths1[i]; 135 136 /* post receives: rvalues - rows I will own; count - nu */ 137 ierr = PetscMalloc3(recvtotal,&rvalues,nrecvs,&source,nrecvs,&recv_waits);CHKERRQ(ierr); 138 count = 0; 139 for (i=0; i<nrecvs; i++) { 140 ierr = MPI_Irecv((rvalues+count),olengths1[i],MPIU_INT,onodes1[i],tag,comm,recv_waits+i);CHKERRQ(ierr); 141 count += olengths1[i]; 142 } 143 144 /* do sends: 145 1) starts[i] gives the starting index in svalues for stuff going to 146 the ith processor 147 */ 148 ierr = PetscMalloc3(cnt,&svalues,nsends,&send_waits,size,&starts);CHKERRQ(ierr); 149 starts[0] = 0; 150 for (i=1; i<size; i++) starts[i] = starts[i-1] + sizes[i-1]; 151 for (i=0; i<cnt; i++) svalues[starts[owner[i]]++] = rows[i]; 152 for (i=0; i<cnt; i++) rows[i] = rows[i] - rstart; 153 red->drows = drows; 154 red->dcnt = dcnt; 155 ierr = PetscFree(rows);CHKERRQ(ierr); 156 157 starts[0] = 0; 158 for (i=1; i<size; i++) starts[i] = starts[i-1] + sizes[i-1]; 159 count = 0; 160 for (i=0; i<size; i++) { 161 if (sizes[i]) { 162 ierr = MPI_Isend(svalues+starts[i],sizes[i],MPIU_INT,i,tag,comm,send_waits+count++);CHKERRQ(ierr); 163 } 164 } 165 166 /* wait on receives */ 167 count = nrecvs; 168 slen = 0; 169 while (count) { 170 ierr = MPI_Waitany(nrecvs,recv_waits,&imdex,&recv_status);CHKERRQ(ierr); 171 /* unpack receives into our local space */ 172 ierr = MPI_Get_count(&recv_status,MPIU_INT,&n);CHKERRQ(ierr); 173 slen += n; 174 count--; 175 } 176 if (slen != recvtotal) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Total message lengths %D not expected %D",slen,recvtotal); 177 178 ierr = ISCreateGeneral(comm,slen,rvalues,PETSC_COPY_VALUES,&red->is);CHKERRQ(ierr); 179 180 /* free up all work space */ 181 ierr = PetscFree(olengths1);CHKERRQ(ierr); 182 ierr = PetscFree(onodes1);CHKERRQ(ierr); 183 ierr = PetscFree3(rvalues,source,recv_waits);CHKERRQ(ierr); 184 ierr = PetscFree2(sizes,owner);CHKERRQ(ierr); 185 if (nsends) { /* wait on sends */ 186 ierr = PetscMalloc1(nsends,&send_status);CHKERRQ(ierr); 187 ierr = MPI_Waitall(nsends,send_waits,send_status);CHKERRQ(ierr); 188 ierr = PetscFree(send_status);CHKERRQ(ierr); 189 } 190 ierr = PetscFree3(svalues,send_waits,starts);CHKERRQ(ierr); 191 ierr = PetscLayoutDestroy(&map);CHKERRQ(ierr); 192 ierr = PetscLayoutDestroy(&nmap);CHKERRQ(ierr); 193 194 ierr = VecCreateMPI(comm,slen,PETSC_DETERMINE,&red->b);CHKERRQ(ierr); 195 ierr = VecDuplicate(red->b,&red->x);CHKERRQ(ierr); 196 ierr = MatCreateVecs(pc->pmat,&tvec,NULL);CHKERRQ(ierr); 197 ierr = VecScatterCreate(tvec,red->is,red->b,NULL,&red->scatter);CHKERRQ(ierr); 198 ierr = VecDestroy(&tvec);CHKERRQ(ierr); 199 ierr = MatCreateSubMatrix(pc->pmat,red->is,red->is,MAT_INITIAL_MATRIX,&tmat);CHKERRQ(ierr); 200 ierr = KSPSetOperators(red->ksp,tmat,tmat);CHKERRQ(ierr); 201 ierr = MatDestroy(&tmat);CHKERRQ(ierr); 202 } 203 204 /* get diagonal portion of matrix */ 205 ierr = PetscFree(red->diag);CHKERRQ(ierr); 206 ierr = PetscMalloc1(red->dcnt,&red->diag);CHKERRQ(ierr); 207 ierr = MatCreateVecs(pc->pmat,&diag,NULL);CHKERRQ(ierr); 208 ierr = MatGetDiagonal(pc->pmat,diag);CHKERRQ(ierr); 209 ierr = VecGetArrayRead(diag,&d);CHKERRQ(ierr); 210 for (i=0; i<red->dcnt; i++) red->diag[i] = 1.0/d[red->drows[i]]; 211 ierr = VecRestoreArrayRead(diag,&d);CHKERRQ(ierr); 212 ierr = VecDestroy(&diag);CHKERRQ(ierr); 213 ierr = KSPSetUp(red->ksp);CHKERRQ(ierr); 214 PetscFunctionReturn(0); 215 } 216 217 static PetscErrorCode PCApply_Redistribute(PC pc,Vec b,Vec x) 218 { 219 PC_Redistribute *red = (PC_Redistribute*)pc->data; 220 PetscErrorCode ierr; 221 PetscInt dcnt = red->dcnt,i; 222 const PetscInt *drows = red->drows; 223 PetscScalar *xwork; 224 const PetscScalar *bwork,*diag = red->diag; 225 226 PetscFunctionBegin; 227 if (!red->work) { 228 ierr = VecDuplicate(b,&red->work);CHKERRQ(ierr); 229 } 230 /* compute the rows of solution that have diagonal entries only */ 231 ierr = VecSet(x,0.0);CHKERRQ(ierr); /* x = diag(A)^{-1} b */ 232 ierr = VecGetArray(x,&xwork);CHKERRQ(ierr); 233 ierr = VecGetArrayRead(b,&bwork);CHKERRQ(ierr); 234 for (i=0; i<dcnt; i++) xwork[drows[i]] = diag[i]*bwork[drows[i]]; 235 ierr = PetscLogFlops(dcnt);CHKERRQ(ierr); 236 ierr = VecRestoreArray(red->work,&xwork);CHKERRQ(ierr); 237 ierr = VecRestoreArrayRead(b,&bwork);CHKERRQ(ierr); 238 /* update the right hand side for the reduced system with diagonal rows (and corresponding columns) removed */ 239 ierr = MatMult(pc->pmat,x,red->work);CHKERRQ(ierr); 240 ierr = VecAYPX(red->work,-1.0,b);CHKERRQ(ierr); /* red->work = b - A x */ 241 242 ierr = VecScatterBegin(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 243 ierr = VecScatterEnd(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 244 ierr = KSPSolve(red->ksp,red->b,red->x);CHKERRQ(ierr); 245 ierr = KSPCheckSolve(red->ksp,pc,red->x);CHKERRQ(ierr); 246 ierr = VecScatterBegin(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 247 ierr = VecScatterEnd(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 248 PetscFunctionReturn(0); 249 } 250 251 static PetscErrorCode PCDestroy_Redistribute(PC pc) 252 { 253 PC_Redistribute *red = (PC_Redistribute*)pc->data; 254 PetscErrorCode ierr; 255 256 PetscFunctionBegin; 257 ierr = VecScatterDestroy(&red->scatter);CHKERRQ(ierr); 258 ierr = ISDestroy(&red->is);CHKERRQ(ierr); 259 ierr = VecDestroy(&red->b);CHKERRQ(ierr); 260 ierr = VecDestroy(&red->x);CHKERRQ(ierr); 261 ierr = KSPDestroy(&red->ksp);CHKERRQ(ierr); 262 ierr = VecDestroy(&red->work);CHKERRQ(ierr); 263 ierr = PetscFree(red->drows);CHKERRQ(ierr); 264 ierr = PetscFree(red->diag);CHKERRQ(ierr); 265 ierr = PetscFree(pc->data);CHKERRQ(ierr); 266 PetscFunctionReturn(0); 267 } 268 269 static PetscErrorCode PCSetFromOptions_Redistribute(PetscOptionItems *PetscOptionsObject,PC pc) 270 { 271 PetscErrorCode ierr; 272 PC_Redistribute *red = (PC_Redistribute*)pc->data; 273 274 PetscFunctionBegin; 275 ierr = KSPSetFromOptions(red->ksp);CHKERRQ(ierr); 276 PetscFunctionReturn(0); 277 } 278 279 /*@ 280 PCRedistributeGetKSP - Gets the KSP created by the PCREDISTRIBUTE 281 282 Not Collective 283 284 Input Parameter: 285 . pc - the preconditioner context 286 287 Output Parameter: 288 . innerksp - the inner KSP 289 290 Level: advanced 291 292 @*/ 293 PetscErrorCode PCRedistributeGetKSP(PC pc,KSP *innerksp) 294 { 295 PC_Redistribute *red = (PC_Redistribute*)pc->data; 296 297 PetscFunctionBegin; 298 PetscValidHeaderSpecific(pc,PC_CLASSID,1); 299 PetscValidPointer(innerksp,2); 300 *innerksp = red->ksp; 301 PetscFunctionReturn(0); 302 } 303 304 /* -------------------------------------------------------------------------------------*/ 305 /*MC 306 PCREDISTRIBUTE - Redistributes a matrix for load balancing, removing the rows that only have a diagonal entry and then applys a KSP to that new matrix 307 308 Options for the redistribute preconditioners can be set with -redistribute_ksp_xxx <values> and -redistribute_pc_xxx <values> 309 310 Notes: 311 Usually run this with -ksp_type preonly 312 313 If you have used MatZeroRows() to eliminate (for example, Dirichlet) boundary conditions for a symmetric problem then you can use, for example, -ksp_type preonly 314 -pc_type redistribute -redistribute_ksp_type cg -redistribute_pc_type bjacobi -redistribute_sub_pc_type icc to take advantage of the symmetry. 315 316 This does NOT call a partitioner to reorder rows to lower communication; the ordering of the rows in the original matrix and redistributed matrix is the same. 317 318 Developer Notes: 319 Should add an option to this preconditioner to use a partitioner to redistribute the rows to lower communication. 320 321 Level: intermediate 322 323 .seealso: PCCreate(), PCSetType(), PCType (for list of available types), PCRedistributeGetKSP() 324 M*/ 325 326 PETSC_EXTERN PetscErrorCode PCCreate_Redistribute(PC pc) 327 { 328 PetscErrorCode ierr; 329 PC_Redistribute *red; 330 const char *prefix; 331 332 PetscFunctionBegin; 333 ierr = PetscNewLog(pc,&red);CHKERRQ(ierr); 334 pc->data = (void*)red; 335 336 pc->ops->apply = PCApply_Redistribute; 337 pc->ops->applytranspose = 0; 338 pc->ops->setup = PCSetUp_Redistribute; 339 pc->ops->destroy = PCDestroy_Redistribute; 340 pc->ops->setfromoptions = PCSetFromOptions_Redistribute; 341 pc->ops->view = PCView_Redistribute; 342 343 ierr = KSPCreate(PetscObjectComm((PetscObject)pc),&red->ksp);CHKERRQ(ierr); 344 ierr = KSPSetErrorIfNotConverged(red->ksp,pc->erroriffailure);CHKERRQ(ierr); 345 ierr = PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);CHKERRQ(ierr); 346 ierr = PetscLogObjectParent((PetscObject)pc,(PetscObject)red->ksp);CHKERRQ(ierr); 347 ierr = PCGetOptionsPrefix(pc,&prefix);CHKERRQ(ierr); 348 ierr = KSPSetOptionsPrefix(red->ksp,prefix);CHKERRQ(ierr); 349 ierr = KSPAppendOptionsPrefix(red->ksp,"redistribute_");CHKERRQ(ierr); 350 PetscFunctionReturn(0); 351 } 352