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 #undef __FUNCT__ 19 #define __FUNCT__ "PCView_Redistribute" 20 static PetscErrorCode PCView_Redistribute(PC pc,PetscViewer viewer) 21 { 22 PC_Redistribute *red = (PC_Redistribute*)pc->data; 23 PetscErrorCode ierr; 24 PetscBool iascii,isstring; 25 PetscInt ncnt,N; 26 27 PetscFunctionBegin; 28 ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr); 29 ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);CHKERRQ(ierr); 30 if (iascii) { 31 ierr = MPI_Allreduce(&red->dcnt,&ncnt,1,MPIU_INT,MPI_SUM,PetscObjectComm((PetscObject)pc));CHKERRQ(ierr); 32 ierr = MatGetSize(pc->pmat,&N,NULL);CHKERRQ(ierr); 33 ierr = PetscViewerASCIIPrintf(viewer," Number rows eliminated %D Percentage rows eliminated %g\n",ncnt,100.0*((PetscReal)ncnt)/((PetscReal)N));CHKERRQ(ierr); 34 ierr = PetscViewerASCIIPrintf(viewer," Redistribute preconditioner: \n");CHKERRQ(ierr); 35 ierr = KSPView(red->ksp,viewer);CHKERRQ(ierr); 36 } else if (isstring) { 37 ierr = PetscViewerStringSPrintf(viewer," Redistribute preconditioner");CHKERRQ(ierr); 38 ierr = KSPView(red->ksp,viewer);CHKERRQ(ierr); 39 } 40 PetscFunctionReturn(0); 41 } 42 43 #undef __FUNCT__ 44 #define __FUNCT__ "PCSetUp_Redistribute" 45 static PetscErrorCode PCSetUp_Redistribute(PC pc) 46 { 47 PC_Redistribute *red = (PC_Redistribute*)pc->data; 48 PetscErrorCode ierr; 49 MPI_Comm comm; 50 PetscInt rstart,rend,i,nz,cnt,*rows,ncnt,dcnt,*drows; 51 PetscLayout map,nmap; 52 PetscMPIInt size,imdex,tag,n; 53 PetscInt *source = NULL; 54 PetscMPIInt *sizes = NULL,nrecvs; 55 PetscInt j,nsends; 56 PetscInt *owner = NULL,*starts = NULL,count,slen; 57 PetscInt *rvalues,*svalues,recvtotal; 58 PetscMPIInt *onodes1,*olengths1; 59 MPI_Request *send_waits = NULL,*recv_waits = NULL; 60 MPI_Status recv_status,*send_status; 61 Vec tvec,diag; 62 Mat tmat; 63 const PetscScalar *d; 64 65 PetscFunctionBegin; 66 if (pc->setupcalled) { 67 ierr = KSPGetOperators(red->ksp,NULL,&tmat);CHKERRQ(ierr); 68 ierr = MatGetSubMatrix(pc->pmat,red->is,red->is,MAT_REUSE_MATRIX,&tmat);CHKERRQ(ierr); 69 ierr = KSPSetOperators(red->ksp,tmat,tmat);CHKERRQ(ierr); 70 } else { 71 PetscInt NN; 72 73 ierr = PetscObjectGetComm((PetscObject)pc,&comm);CHKERRQ(ierr); 74 ierr = MPI_Comm_size(comm,&size);CHKERRQ(ierr); 75 ierr = PetscObjectGetNewTag((PetscObject)pc,&tag);CHKERRQ(ierr); 76 77 /* count non-diagonal rows on process */ 78 ierr = MatGetOwnershipRange(pc->mat,&rstart,&rend);CHKERRQ(ierr); 79 cnt = 0; 80 for (i=rstart; i<rend; i++) { 81 ierr = MatGetRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 82 if (nz > 1) cnt++; 83 ierr = MatRestoreRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 84 } 85 ierr = PetscMalloc1(cnt,&rows);CHKERRQ(ierr); 86 ierr = PetscMalloc1(rend - rstart - cnt,&drows);CHKERRQ(ierr); 87 88 /* list non-diagonal rows on process */ 89 cnt = 0; dcnt = 0; 90 for (i=rstart; i<rend; i++) { 91 ierr = MatGetRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 92 if (nz > 1) rows[cnt++] = i; 93 else drows[dcnt++] = i - rstart; 94 ierr = MatRestoreRow(pc->mat,i,&nz,NULL,NULL);CHKERRQ(ierr); 95 } 96 97 /* create PetscLayout for non-diagonal rows on each process */ 98 ierr = PetscLayoutCreate(comm,&map);CHKERRQ(ierr); 99 ierr = PetscLayoutSetLocalSize(map,cnt);CHKERRQ(ierr); 100 ierr = PetscLayoutSetBlockSize(map,1);CHKERRQ(ierr); 101 ierr = PetscLayoutSetUp(map);CHKERRQ(ierr); 102 rstart = map->rstart; 103 rend = map->rend; 104 105 /* create PetscLayout for load-balanced non-diagonal rows on each process */ 106 ierr = PetscLayoutCreate(comm,&nmap);CHKERRQ(ierr); 107 ierr = MPI_Allreduce(&cnt,&ncnt,1,MPIU_INT,MPI_SUM,comm);CHKERRQ(ierr); 108 ierr = PetscLayoutSetSize(nmap,ncnt);CHKERRQ(ierr); 109 ierr = PetscLayoutSetBlockSize(nmap,1);CHKERRQ(ierr); 110 ierr = PetscLayoutSetUp(nmap);CHKERRQ(ierr); 111 112 ierr = MatGetSize(pc->pmat,&NN,NULL);CHKERRQ(ierr); 113 ierr = PetscInfo2(pc,"Number of diagonal rows eliminated %d, percentage eliminated %g\n",NN-ncnt,((PetscReal)(NN-ncnt))/((PetscReal)(NN)));CHKERRQ(ierr); 114 /* 115 this code is taken from VecScatterCreate_PtoS() 116 Determines what rows need to be moved where to 117 load balance the non-diagonal rows 118 */ 119 /* count number of contributors to each processor */ 120 ierr = PetscMalloc2(size,&sizes,cnt,&owner);CHKERRQ(ierr); 121 ierr = PetscMemzero(sizes,size*sizeof(PetscMPIInt));CHKERRQ(ierr); 122 j = 0; 123 nsends = 0; 124 for (i=rstart; i<rend; i++) { 125 if (i < nmap->range[j]) j = 0; 126 for (; j<size; j++) { 127 if (i < nmap->range[j+1]) { 128 if (!sizes[j]++) nsends++; 129 owner[i-rstart] = j; 130 break; 131 } 132 } 133 } 134 /* inform other processors of number of messages and max length*/ 135 ierr = PetscGatherNumberOfMessages(comm,NULL,sizes,&nrecvs);CHKERRQ(ierr); 136 ierr = PetscGatherMessageLengths(comm,nsends,nrecvs,sizes,&onodes1,&olengths1);CHKERRQ(ierr); 137 ierr = PetscSortMPIIntWithArray(nrecvs,onodes1,olengths1);CHKERRQ(ierr); 138 recvtotal = 0; for (i=0; i<nrecvs; i++) recvtotal += olengths1[i]; 139 140 /* post receives: rvalues - rows I will own; count - nu */ 141 ierr = PetscMalloc3(recvtotal,&rvalues,nrecvs,&source,nrecvs,&recv_waits);CHKERRQ(ierr); 142 count = 0; 143 for (i=0; i<nrecvs; i++) { 144 ierr = MPI_Irecv((rvalues+count),olengths1[i],MPIU_INT,onodes1[i],tag,comm,recv_waits+i);CHKERRQ(ierr); 145 count += olengths1[i]; 146 } 147 148 /* do sends: 149 1) starts[i] gives the starting index in svalues for stuff going to 150 the ith processor 151 */ 152 ierr = PetscMalloc3(cnt,&svalues,nsends,&send_waits,size,&starts);CHKERRQ(ierr); 153 starts[0] = 0; 154 for (i=1; i<size; i++) starts[i] = starts[i-1] + sizes[i-1]; 155 for (i=0; i<cnt; i++) svalues[starts[owner[i]]++] = rows[i]; 156 for (i=0; i<cnt; i++) rows[i] = rows[i] - rstart; 157 red->drows = drows; 158 red->dcnt = dcnt; 159 ierr = PetscFree(rows);CHKERRQ(ierr); 160 161 starts[0] = 0; 162 for (i=1; i<size; i++) starts[i] = starts[i-1] + sizes[i-1]; 163 count = 0; 164 for (i=0; i<size; i++) { 165 if (sizes[i]) { 166 ierr = MPI_Isend(svalues+starts[i],sizes[i],MPIU_INT,i,tag,comm,send_waits+count++);CHKERRQ(ierr); 167 } 168 } 169 170 /* wait on receives */ 171 count = nrecvs; 172 slen = 0; 173 while (count) { 174 ierr = MPI_Waitany(nrecvs,recv_waits,&imdex,&recv_status);CHKERRQ(ierr); 175 /* unpack receives into our local space */ 176 ierr = MPI_Get_count(&recv_status,MPIU_INT,&n);CHKERRQ(ierr); 177 slen += n; 178 count--; 179 } 180 if (slen != recvtotal) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Total message lengths %D not expected %D",slen,recvtotal); 181 182 ierr = ISCreateGeneral(comm,slen,rvalues,PETSC_COPY_VALUES,&red->is);CHKERRQ(ierr); 183 184 /* free up all work space */ 185 ierr = PetscFree(olengths1);CHKERRQ(ierr); 186 ierr = PetscFree(onodes1);CHKERRQ(ierr); 187 ierr = PetscFree3(rvalues,source,recv_waits);CHKERRQ(ierr); 188 ierr = PetscFree2(sizes,owner);CHKERRQ(ierr); 189 if (nsends) { /* wait on sends */ 190 ierr = PetscMalloc1(nsends,&send_status);CHKERRQ(ierr); 191 ierr = MPI_Waitall(nsends,send_waits,send_status);CHKERRQ(ierr); 192 ierr = PetscFree(send_status);CHKERRQ(ierr); 193 } 194 ierr = PetscFree3(svalues,send_waits,starts);CHKERRQ(ierr); 195 ierr = PetscLayoutDestroy(&map);CHKERRQ(ierr); 196 ierr = PetscLayoutDestroy(&nmap);CHKERRQ(ierr); 197 198 ierr = VecCreateMPI(comm,slen,PETSC_DETERMINE,&red->b);CHKERRQ(ierr); 199 ierr = VecDuplicate(red->b,&red->x);CHKERRQ(ierr); 200 ierr = MatCreateVecs(pc->pmat,&tvec,NULL);CHKERRQ(ierr); 201 ierr = VecScatterCreate(tvec,red->is,red->b,NULL,&red->scatter);CHKERRQ(ierr); 202 ierr = VecDestroy(&tvec);CHKERRQ(ierr); 203 ierr = MatGetSubMatrix(pc->pmat,red->is,red->is,MAT_INITIAL_MATRIX,&tmat);CHKERRQ(ierr); 204 ierr = KSPSetOperators(red->ksp,tmat,tmat);CHKERRQ(ierr); 205 ierr = MatDestroy(&tmat);CHKERRQ(ierr); 206 } 207 208 /* get diagonal portion of matrix */ 209 ierr = PetscFree(red->diag);CHKERRQ(ierr); 210 ierr = PetscMalloc1(red->dcnt,&red->diag);CHKERRQ(ierr); 211 ierr = MatCreateVecs(pc->pmat,&diag,NULL);CHKERRQ(ierr); 212 ierr = MatGetDiagonal(pc->pmat,diag);CHKERRQ(ierr); 213 ierr = VecGetArrayRead(diag,&d);CHKERRQ(ierr); 214 for (i=0; i<red->dcnt; i++) red->diag[i] = 1.0/d[red->drows[i]]; 215 ierr = VecRestoreArrayRead(diag,&d);CHKERRQ(ierr); 216 ierr = VecDestroy(&diag);CHKERRQ(ierr); 217 ierr = KSPSetUp(red->ksp);CHKERRQ(ierr); 218 PetscFunctionReturn(0); 219 } 220 221 #undef __FUNCT__ 222 #define __FUNCT__ "PCApply_Redistribute" 223 static PetscErrorCode PCApply_Redistribute(PC pc,Vec b,Vec x) 224 { 225 PC_Redistribute *red = (PC_Redistribute*)pc->data; 226 PetscErrorCode ierr; 227 PetscInt dcnt = red->dcnt,i; 228 const PetscInt *drows = red->drows; 229 PetscScalar *xwork; 230 const PetscScalar *bwork,*diag = red->diag; 231 232 PetscFunctionBegin; 233 if (!red->work) { 234 ierr = VecDuplicate(b,&red->work);CHKERRQ(ierr); 235 } 236 /* compute the rows of solution that have diagonal entries only */ 237 ierr = VecSet(x,0.0);CHKERRQ(ierr); /* x = diag(A)^{-1} b */ 238 ierr = VecGetArray(x,&xwork);CHKERRQ(ierr); 239 ierr = VecGetArrayRead(b,&bwork);CHKERRQ(ierr); 240 for (i=0; i<dcnt; i++) xwork[drows[i]] = diag[i]*bwork[drows[i]]; 241 ierr = PetscLogFlops(dcnt);CHKERRQ(ierr); 242 ierr = VecRestoreArray(red->work,&xwork);CHKERRQ(ierr); 243 ierr = VecRestoreArrayRead(b,&bwork);CHKERRQ(ierr); 244 /* update the right hand side for the reduced system with diagonal rows (and corresponding columns) removed */ 245 ierr = MatMult(pc->pmat,x,red->work);CHKERRQ(ierr); 246 ierr = VecAYPX(red->work,-1.0,b);CHKERRQ(ierr); /* red->work = b - A x */ 247 248 ierr = VecScatterBegin(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 249 ierr = VecScatterEnd(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 250 ierr = KSPSolve(red->ksp,red->b,red->x);CHKERRQ(ierr); 251 ierr = VecScatterBegin(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 252 ierr = VecScatterEnd(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 253 PetscFunctionReturn(0); 254 } 255 256 #undef __FUNCT__ 257 #define __FUNCT__ "PCDestroy_Redistribute" 258 static PetscErrorCode PCDestroy_Redistribute(PC pc) 259 { 260 PC_Redistribute *red = (PC_Redistribute*)pc->data; 261 PetscErrorCode ierr; 262 263 PetscFunctionBegin; 264 ierr = VecScatterDestroy(&red->scatter);CHKERRQ(ierr); 265 ierr = ISDestroy(&red->is);CHKERRQ(ierr); 266 ierr = VecDestroy(&red->b);CHKERRQ(ierr); 267 ierr = VecDestroy(&red->x);CHKERRQ(ierr); 268 ierr = KSPDestroy(&red->ksp);CHKERRQ(ierr); 269 ierr = VecDestroy(&red->work);CHKERRQ(ierr); 270 ierr = PetscFree(red->drows);CHKERRQ(ierr); 271 ierr = PetscFree(red->diag);CHKERRQ(ierr); 272 ierr = PetscFree(pc->data);CHKERRQ(ierr); 273 PetscFunctionReturn(0); 274 } 275 276 #undef __FUNCT__ 277 #define __FUNCT__ "PCSetFromOptions_Redistribute" 278 static PetscErrorCode PCSetFromOptions_Redistribute(PetscOptions *PetscOptionsObject,PC pc) 279 { 280 PetscErrorCode ierr; 281 PC_Redistribute *red = (PC_Redistribute*)pc->data; 282 283 PetscFunctionBegin; 284 ierr = KSPSetFromOptions(red->ksp);CHKERRQ(ierr); 285 PetscFunctionReturn(0); 286 } 287 288 #undef __FUNCT__ 289 #define __FUNCT__ "PCRedistributeGetKSP" 290 /*@ 291 PCRedistributeGetKSP - Gets the KSP created by the PCREDISTRIBUTE 292 293 Not Collective 294 295 Input Parameter: 296 . pc - the preconditioner context 297 298 Output Parameter: 299 . innerksp - the inner KSP 300 301 Level: advanced 302 303 .keywords: PC, redistribute solve 304 @*/ 305 PetscErrorCode PCRedistributeGetKSP(PC pc,KSP *innerksp) 306 { 307 PC_Redistribute *red = (PC_Redistribute*)pc->data; 308 309 PetscFunctionBegin; 310 PetscValidHeaderSpecific(pc,PC_CLASSID,1); 311 PetscValidPointer(innerksp,2); 312 *innerksp = red->ksp; 313 PetscFunctionReturn(0); 314 } 315 316 /* -------------------------------------------------------------------------------------*/ 317 /*MC 318 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 319 320 Options for the redistribute preconditioners can be set with -redistribute_ksp_xxx <values> and -redistribute_pc_xxx <values> 321 322 Notes: Usually run this with -ksp_type preonly 323 324 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 325 -pc_type redistribute -redistribute_ksp_type cg -redistribute_pc_type bjacobi -redistribute_sub_pc_type icc to take advantage of the symmetry. 326 327 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. 328 329 Developer Notes: Should add an option to this preconditioner to use a partitioner to redistribute the rows to lower communication. 330 331 Level: intermediate 332 333 .seealso: PCCreate(), PCSetType(), PCType (for list of available types), PCRedistributeGetKSP() 334 M*/ 335 336 #undef __FUNCT__ 337 #define __FUNCT__ "PCCreate_Redistribute" 338 PETSC_EXTERN PetscErrorCode PCCreate_Redistribute(PC pc) 339 { 340 PetscErrorCode ierr; 341 PC_Redistribute *red; 342 const char *prefix; 343 344 PetscFunctionBegin; 345 ierr = PetscNewLog(pc,&red);CHKERRQ(ierr); 346 pc->data = (void*)red; 347 348 pc->ops->apply = PCApply_Redistribute; 349 pc->ops->applytranspose = 0; 350 pc->ops->setup = PCSetUp_Redistribute; 351 pc->ops->destroy = PCDestroy_Redistribute; 352 pc->ops->setfromoptions = PCSetFromOptions_Redistribute; 353 pc->ops->view = PCView_Redistribute; 354 355 ierr = KSPCreate(PetscObjectComm((PetscObject)pc),&red->ksp);CHKERRQ(ierr); 356 ierr = KSPSetErrorIfNotConverged(red->ksp,pc->erroriffailure);CHKERRQ(ierr); 357 ierr = PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);CHKERRQ(ierr); 358 ierr = PetscLogObjectParent((PetscObject)pc,(PetscObject)red->ksp);CHKERRQ(ierr); 359 ierr = PCGetOptionsPrefix(pc,&prefix);CHKERRQ(ierr); 360 ierr = KSPSetOptionsPrefix(red->ksp,prefix);CHKERRQ(ierr); 361 ierr = KSPAppendOptionsPrefix(red->ksp,"redistribute_");CHKERRQ(ierr); 362 PetscFunctionReturn(0); 363 } 364