1 #define PETSCKSP_DLL 2 3 /* 4 This file defines a "solve the problem redistributely on each subgroup of processor" preconditioner. 5 */ 6 #include "private/pcimpl.h" /*I "petscpc.h" I*/ 7 #include "petscksp.h" 8 9 typedef struct { 10 KSP ksp; 11 Vec x,b; 12 VecScatter scatter; 13 IS is; 14 PetscInt dcnt,*drows; /* these are the local rows that have only diagonal entry */ 15 PetscScalar *diag; 16 Vec work; 17 } PC_Redistribute; 18 19 #undef __FUNCT__ 20 #define __FUNCT__ "PCView_Redistribute" 21 static PetscErrorCode PCView_Redistribute(PC pc,PetscViewer viewer) 22 { 23 PC_Redistribute *red = (PC_Redistribute*)pc->data; 24 PetscErrorCode ierr; 25 PetscTruth iascii,isstring; 26 PetscInt ncnt,N; 27 28 PetscFunctionBegin; 29 ierr = PetscTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr); 30 ierr = PetscTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);CHKERRQ(ierr); 31 if (iascii) { 32 ierr = MPI_Allreduce(&red->dcnt,&ncnt,1,MPIU_INT,MPI_SUM,((PetscObject)pc)->comm);CHKERRQ(ierr); 33 ierr = MatGetSize(pc->pmat,&N,PETSC_NULL);CHKERRQ(ierr); 34 ierr = PetscViewerASCIIPrintf(viewer," Number rows eliminated %D Percentage rows eliminated %g\n",ncnt,100.0*((PetscReal)ncnt)/((PetscReal)N));CHKERRQ(ierr); 35 ierr = PetscViewerASCIIPrintf(viewer," Redistribute preconditioner: \n");CHKERRQ(ierr); 36 ierr = KSPView(red->ksp,viewer);CHKERRQ(ierr); 37 } else if (isstring) { 38 ierr = PetscViewerStringSPrintf(viewer," Redistribute preconditioner");CHKERRQ(ierr); 39 ierr = KSPView(red->ksp,viewer);CHKERRQ(ierr); 40 } else { 41 SETERRQ1(((PetscObject)pc)->comm,PETSC_ERR_SUP,"Viewer type %s not supported for PC redistribute",((PetscObject)viewer)->type_name); 42 } 43 PetscFunctionReturn(0); 44 } 45 46 #undef __FUNCT__ 47 #define __FUNCT__ "PCSetUp_Redistribute" 48 static PetscErrorCode PCSetUp_Redistribute(PC pc) 49 { 50 PC_Redistribute *red = (PC_Redistribute*)pc->data; 51 PetscErrorCode ierr; 52 MPI_Comm comm; 53 PetscInt rstart,rend,i,nz,cnt,*rows,ncnt,dcnt,*drows; 54 PetscLayout map,nmap; 55 PetscMPIInt size,rank,imdex,tag,n; 56 PetscInt *source = PETSC_NULL; 57 PetscMPIInt *nprocs = PETSC_NULL,nrecvs; 58 PetscInt j,nsends; 59 PetscInt *owner = PETSC_NULL,*starts = PETSC_NULL,count,slen; 60 PetscInt *rvalues,*svalues,recvtotal; 61 PetscMPIInt *onodes1,*olengths1; 62 MPI_Request *send_waits = PETSC_NULL,*recv_waits = PETSC_NULL; 63 MPI_Status recv_status,*send_status; 64 Vec tvec,diag; 65 Mat tmat; 66 const PetscScalar *d; 67 68 PetscFunctionBegin; 69 if (pc->setupcalled) { 70 ierr = KSPGetOperators(red->ksp,PETSC_NULL,&tmat,PETSC_NULL);CHKERRQ(ierr); 71 ierr = MatGetSubMatrix(pc->pmat,red->is,red->is,MAT_REUSE_MATRIX,&tmat);CHKERRQ(ierr); 72 ierr = KSPSetOperators(red->ksp,tmat,tmat,SAME_NONZERO_PATTERN);CHKERRQ(ierr); 73 } else { 74 PetscInt NN; 75 76 ierr = PetscObjectGetComm((PetscObject)pc,&comm);CHKERRQ(ierr); 77 ierr = MPI_Comm_size(comm,&size);CHKERRQ(ierr); 78 ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr); 79 ierr = PetscObjectGetNewTag((PetscObject)pc,&tag);CHKERRQ(ierr); 80 81 /* count non-diagonal rows on process */ 82 ierr = MatGetOwnershipRange(pc->mat,&rstart,&rend);CHKERRQ(ierr); 83 cnt = 0; 84 for (i=rstart; i<rend; i++) { 85 ierr = MatGetRow(pc->mat,i,&nz,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr); 86 if (nz > 1) cnt++; 87 ierr = MatRestoreRow(pc->mat,i,&nz,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr); 88 } 89 ierr = PetscMalloc(cnt*sizeof(PetscInt),&rows);CHKERRQ(ierr); 90 ierr = PetscMalloc((rend - rstart - cnt)*sizeof(PetscInt),&drows);CHKERRQ(ierr); 91 92 /* list non-diagonal rows on process */ 93 cnt = 0; dcnt = 0; 94 for (i=rstart; i<rend; i++) { 95 ierr = MatGetRow(pc->mat,i,&nz,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr); 96 if (nz > 1) rows[cnt++] = i; 97 else drows[dcnt++] = i - rstart; 98 ierr = MatRestoreRow(pc->mat,i,&nz,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr); 99 } 100 101 /* create PetscLayout for non-diagonal rows on each process */ 102 ierr = PetscLayoutCreate(comm,&map);CHKERRQ(ierr); 103 ierr = PetscLayoutSetLocalSize(map,cnt);CHKERRQ(ierr); 104 ierr = PetscLayoutSetBlockSize(map,1);CHKERRQ(ierr); 105 ierr = PetscLayoutSetUp(map);CHKERRQ(ierr); 106 rstart = map->rstart; 107 rend = map->rend; 108 109 /* create PetscLayout for load-balanced non-diagonal rows on each process */ 110 ierr = PetscLayoutCreate(comm,&nmap);CHKERRQ(ierr); 111 ierr = MPI_Allreduce(&cnt,&ncnt,1,MPIU_INT,MPI_SUM,comm);CHKERRQ(ierr); 112 ierr = PetscLayoutSetSize(nmap,ncnt);CHKERRQ(ierr); 113 ierr = PetscLayoutSetBlockSize(nmap,1);CHKERRQ(ierr); 114 ierr = PetscLayoutSetUp(nmap);CHKERRQ(ierr); 115 116 ierr = MatGetSize(pc->pmat,&NN,PETSC_NULL);CHKERRQ(ierr); 117 ierr = PetscInfo2(pc,"Number of diagonal rows eliminated %d, percentage eliminated %g\n",NN-ncnt,((PetscReal)(NN-ncnt))/((PetscReal)(NN))); 118 /* 119 this code is taken from VecScatterCreate_PtoS() 120 Determines what rows need to be moved where to 121 load balance the non-diagonal rows 122 */ 123 /* count number of contributors to each processor */ 124 ierr = PetscMalloc2(size,PetscMPIInt,&nprocs,cnt,PetscInt,&owner);CHKERRQ(ierr); 125 ierr = PetscMemzero(nprocs,size*sizeof(PetscMPIInt));CHKERRQ(ierr); 126 j = 0; 127 nsends = 0; 128 for (i=rstart; i<rend; i++) { 129 if (i < nmap->range[j]) j = 0; 130 for (; j<size; j++) { 131 if (i < nmap->range[j+1]) { 132 if (!nprocs[j]++) nsends++; 133 owner[i-rstart] = j; 134 break; 135 } 136 } 137 } 138 /* inform other processors of number of messages and max length*/ 139 ierr = PetscGatherNumberOfMessages(comm,PETSC_NULL,nprocs,&nrecvs);CHKERRQ(ierr); 140 ierr = PetscGatherMessageLengths(comm,nsends,nrecvs,nprocs,&onodes1,&olengths1);CHKERRQ(ierr); 141 ierr = PetscSortMPIIntWithArray(nrecvs,onodes1,olengths1);CHKERRQ(ierr); 142 recvtotal = 0; for (i=0; i<nrecvs; i++) recvtotal += olengths1[i]; 143 144 /* post receives: rvalues - rows I will own; count - nu */ 145 ierr = PetscMalloc3(recvtotal,PetscInt,&rvalues,nrecvs,PetscInt,&source,nrecvs,MPI_Request,&recv_waits);CHKERRQ(ierr); 146 count = 0; 147 for (i=0; i<nrecvs; i++) { 148 ierr = MPI_Irecv((rvalues+count),olengths1[i],MPIU_INT,onodes1[i],tag,comm,recv_waits+i);CHKERRQ(ierr); 149 count += olengths1[i]; 150 } 151 152 /* do sends: 153 1) starts[i] gives the starting index in svalues for stuff going to 154 the ith processor 155 */ 156 ierr = PetscMalloc3(cnt,PetscInt,&svalues,nsends,MPI_Request,&send_waits,size,PetscInt,&starts);CHKERRQ(ierr); 157 starts[0] = 0; 158 for (i=1; i<size; i++) { starts[i] = starts[i-1] + nprocs[i-1];} 159 for (i=0; i<cnt; i++) { 160 svalues[starts[owner[i]]++] = rows[i]; 161 } 162 for (i=0; i<cnt; i++) rows[i] = rows[i] - rstart; 163 red->drows = drows; 164 red->dcnt = dcnt; 165 ierr = PetscFree(rows);CHKERRQ(ierr); 166 167 starts[0] = 0; 168 for (i=1; i<size; i++) { starts[i] = starts[i-1] + nprocs[i-1];} 169 count = 0; 170 for (i=0; i<size; i++) { 171 if (nprocs[i]) { 172 ierr = MPI_Isend(svalues+starts[i],nprocs[i],MPIU_INT,i,tag,comm,send_waits+count++);CHKERRQ(ierr); 173 } 174 } 175 176 /* wait on receives */ 177 count = nrecvs; 178 slen = 0; 179 while (count) { 180 ierr = MPI_Waitany(nrecvs,recv_waits,&imdex,&recv_status);CHKERRQ(ierr); 181 /* unpack receives into our local space */ 182 ierr = MPI_Get_count(&recv_status,MPIU_INT,&n);CHKERRQ(ierr); 183 slen += n; 184 count--; 185 } 186 if (slen != recvtotal) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Total message lengths %D not expected %D",slen,recvtotal); 187 188 ierr = ISCreateGeneral(comm,slen,rvalues,&red->is);CHKERRQ(ierr); 189 190 /* free up all work space */ 191 ierr = PetscFree(olengths1);CHKERRQ(ierr); 192 ierr = PetscFree(onodes1);CHKERRQ(ierr); 193 ierr = PetscFree3(rvalues,source,recv_waits);CHKERRQ(ierr); 194 ierr = PetscFree2(nprocs,owner);CHKERRQ(ierr); 195 if (nsends) { /* wait on sends */ 196 ierr = PetscMalloc(nsends*sizeof(MPI_Status),&send_status);CHKERRQ(ierr); 197 ierr = MPI_Waitall(nsends,send_waits,send_status);CHKERRQ(ierr); 198 ierr = PetscFree(send_status);CHKERRQ(ierr); 199 } 200 ierr = PetscFree3(svalues,send_waits,starts);CHKERRQ(ierr); 201 ierr = PetscLayoutDestroy(map);CHKERRQ(ierr); 202 ierr = PetscLayoutDestroy(nmap);CHKERRQ(ierr); 203 204 ierr = VecCreateMPI(comm,slen,PETSC_DETERMINE,&red->b);CHKERRQ(ierr); 205 ierr = VecDuplicate(red->b,&red->x);CHKERRQ(ierr); 206 ierr = MatGetVecs(pc->pmat,&tvec,PETSC_NULL);CHKERRQ(ierr); 207 ierr = VecScatterCreate(tvec,red->is,red->b,PETSC_NULL,&red->scatter);CHKERRQ(ierr); 208 ierr = VecDestroy(tvec);CHKERRQ(ierr); 209 ierr = MatGetSubMatrix(pc->pmat,red->is,red->is,MAT_INITIAL_MATRIX,&tmat);CHKERRQ(ierr); 210 ierr = KSPSetOperators(red->ksp,tmat,tmat,SAME_NONZERO_PATTERN);CHKERRQ(ierr); 211 ierr = MatDestroy(tmat);CHKERRQ(ierr); 212 } 213 214 /* get diagonal portion of matrix */ 215 ierr = PetscMalloc(red->dcnt*sizeof(PetscScalar),&red->diag);CHKERRQ(ierr); 216 ierr = MatGetVecs(pc->pmat,&diag,PETSC_NULL);CHKERRQ(ierr); 217 ierr = MatGetDiagonal(pc->pmat,diag);CHKERRQ(ierr); 218 ierr = VecGetArrayRead(diag,&d);CHKERRQ(ierr); 219 for (i=0; i<red->dcnt; i++) { 220 red->diag[i] = 1.0/d[red->drows[i]]; 221 } 222 ierr = VecRestoreArrayRead(diag,&d);CHKERRQ(ierr); 223 ierr = VecDestroy(diag);CHKERRQ(ierr); 224 ierr = KSPSetUp(red->ksp);CHKERRQ(ierr); 225 PetscFunctionReturn(0); 226 } 227 228 #undef __FUNCT__ 229 #define __FUNCT__ "PCApply_Redistribute" 230 static PetscErrorCode PCApply_Redistribute(PC pc,Vec b,Vec x) 231 { 232 PC_Redistribute *red = (PC_Redistribute*)pc->data; 233 PetscErrorCode ierr; 234 PetscInt dcnt = red->dcnt,i; 235 const PetscInt *drows = red->drows; 236 PetscScalar *xwork; 237 const PetscScalar *bwork,*diag = red->diag; 238 239 PetscFunctionBegin; 240 if (!red->work) { 241 ierr = VecDuplicate(b,&red->work);CHKERRQ(ierr); 242 } 243 /* compute the rows of solution that have diagonal entries only */ 244 ierr = VecSet(x,0.0);CHKERRQ(ierr); /* x = diag(A)^{-1} b */ 245 ierr = VecGetArray(x,&xwork);CHKERRQ(ierr); 246 ierr = VecGetArrayRead(b,&bwork);CHKERRQ(ierr); 247 for (i=0; i<dcnt; i++) { 248 xwork[drows[i]] = diag[i]*bwork[drows[i]]; 249 } 250 ierr = PetscLogFlops(dcnt);CHKERRQ(ierr); 251 ierr = VecRestoreArray(red->work,&xwork);CHKERRQ(ierr); 252 ierr = VecRestoreArrayRead(b,&bwork);CHKERRQ(ierr); 253 /* update the right hand side for the reduced system with diagonal rows (and corresponding columns) removed */ 254 ierr = MatMult(pc->pmat,x,red->work);CHKERRQ(ierr); 255 ierr = VecAYPX(red->work,-1.0,b);CHKERRQ(ierr); /* red->work = b - A x */ 256 257 ierr = VecScatterBegin(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 258 ierr = VecScatterEnd(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 259 ierr = KSPSolve(red->ksp,red->b,red->x);CHKERRQ(ierr); 260 ierr = VecScatterBegin(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 261 ierr = VecScatterEnd(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 262 PetscFunctionReturn(0); 263 } 264 265 #undef __FUNCT__ 266 #define __FUNCT__ "PCDestroy_Redistribute" 267 static PetscErrorCode PCDestroy_Redistribute(PC pc) 268 { 269 PC_Redistribute *red = (PC_Redistribute*)pc->data; 270 PetscErrorCode ierr; 271 272 PetscFunctionBegin; 273 if (red->scatter) {ierr = VecScatterDestroy(red->scatter);CHKERRQ(ierr);} 274 if (red->is) {ierr = ISDestroy(red->is);CHKERRQ(ierr);} 275 if (red->b) {ierr = VecDestroy(red->b);CHKERRQ(ierr);} 276 if (red->x) {ierr = VecDestroy(red->x);CHKERRQ(ierr);} 277 if (red->ksp) {ierr = KSPDestroy(red->ksp);CHKERRQ(ierr);} 278 if (red->work) {ierr = VecDestroy(red->work);CHKERRQ(ierr);} 279 ierr = PetscFree(red->drows); 280 ierr = PetscFree(red->diag); 281 ierr = PetscFree(red);CHKERRQ(ierr); 282 PetscFunctionReturn(0); 283 } 284 285 #undef __FUNCT__ 286 #define __FUNCT__ "PCSetFromOptions_Redistribute" 287 static PetscErrorCode PCSetFromOptions_Redistribute(PC pc) 288 { 289 PetscErrorCode ierr; 290 PC_Redistribute *red = (PC_Redistribute*)pc->data; 291 292 PetscFunctionBegin; 293 ierr = KSPSetFromOptions(red->ksp);CHKERRQ(ierr); 294 PetscFunctionReturn(0); 295 } 296 297 /* -------------------------------------------------------------------------------------*/ 298 /*MC 299 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 300 301 Options for the redistribute preconditioners can be set with -redistribute_ksp_xxx <values> and -redistribute_pc_xxx <values> 302 303 Notes: Usually run this with -ksp_type preonly 304 305 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 306 -pc_type redistribute -redistribute_ksp_type cg -redistribute_pc_type bjacobi -redistribute_sub_pc_type icc to take advantage of the symmetry. 307 308 Level: intermediate 309 310 .seealso: PCCreate(), PCSetType(), PCType (for list of available types) 311 M*/ 312 313 EXTERN_C_BEGIN 314 #undef __FUNCT__ 315 #define __FUNCT__ "PCCreate_Redistribute" 316 PetscErrorCode PETSCKSP_DLLEXPORT PCCreate_Redistribute(PC pc) 317 { 318 PetscErrorCode ierr; 319 PC_Redistribute *red; 320 const char *prefix; 321 322 PetscFunctionBegin; 323 ierr = PetscNewLog(pc,PC_Redistribute,&red);CHKERRQ(ierr); 324 pc->data = (void*)red; 325 326 pc->ops->apply = PCApply_Redistribute; 327 pc->ops->applytranspose = 0; 328 pc->ops->setup = PCSetUp_Redistribute; 329 pc->ops->destroy = PCDestroy_Redistribute; 330 pc->ops->setfromoptions = PCSetFromOptions_Redistribute; 331 pc->ops->view = PCView_Redistribute; 332 333 ierr = KSPCreate(((PetscObject)pc)->comm,&red->ksp);CHKERRQ(ierr); 334 ierr = PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);CHKERRQ(ierr); 335 ierr = PetscLogObjectParent(pc,red->ksp);CHKERRQ(ierr); 336 ierr = PCGetOptionsPrefix(pc,&prefix);CHKERRQ(ierr); 337 ierr = KSPSetOptionsPrefix(red->ksp,prefix);CHKERRQ(ierr); 338 ierr = KSPAppendOptionsPrefix(red->ksp,"redistribute_");CHKERRQ(ierr); 339 PetscFunctionReturn(0); 340 } 341 EXTERN_C_END 342