1 2 /* 3 This file defines a "solve the problem redistributely on each subgroup of processor" preconditioner. 4 */ 5 #include <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 = PetscTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr); 29 ierr = PetscTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);CHKERRQ(ierr); 30 if (iascii) { 31 ierr = MPI_Allreduce(&red->dcnt,&ncnt,1,MPIU_INT,MPI_SUM,((PetscObject)pc)->comm);CHKERRQ(ierr); 32 ierr = MatGetSize(pc->pmat,&N,PETSC_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 } else SETERRQ1(((PetscObject)pc)->comm,PETSC_ERR_SUP,"Viewer type %s not supported for PC redistribute",((PetscObject)viewer)->type_name); 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 = PETSC_NULL; 54 PetscMPIInt *nprocs = PETSC_NULL,nrecvs; 55 PetscInt j,nsends; 56 PetscInt *owner = PETSC_NULL,*starts = PETSC_NULL,count,slen; 57 PetscInt *rvalues,*svalues,recvtotal; 58 PetscMPIInt *onodes1,*olengths1; 59 MPI_Request *send_waits = PETSC_NULL,*recv_waits = PETSC_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,PETSC_NULL,&tmat,PETSC_NULL);CHKERRQ(ierr); 68 ierr = MatGetSubMatrix(pc->pmat,red->is,red->is,MAT_REUSE_MATRIX,&tmat);CHKERRQ(ierr); 69 ierr = KSPSetOperators(red->ksp,tmat,tmat,SAME_NONZERO_PATTERN);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,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr); 82 if (nz > 1) cnt++; 83 ierr = MatRestoreRow(pc->mat,i,&nz,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr); 84 } 85 ierr = PetscMalloc(cnt*sizeof(PetscInt),&rows);CHKERRQ(ierr); 86 ierr = PetscMalloc((rend - rstart - cnt)*sizeof(PetscInt),&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,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr); 92 if (nz > 1) rows[cnt++] = i; 93 else drows[dcnt++] = i - rstart; 94 ierr = MatRestoreRow(pc->mat,i,&nz,PETSC_NULL,PETSC_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,PETSC_NULL);CHKERRQ(ierr); 113 ierr = PetscInfo2(pc,"Number of diagonal rows eliminated %d, percentage eliminated %g\n",NN-ncnt,((PetscReal)(NN-ncnt))/((PetscReal)(NN))); 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,PetscMPIInt,&nprocs,cnt,PetscInt,&owner);CHKERRQ(ierr); 121 ierr = PetscMemzero(nprocs,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 (!nprocs[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,PETSC_NULL,nprocs,&nrecvs);CHKERRQ(ierr); 136 ierr = PetscGatherMessageLengths(comm,nsends,nrecvs,nprocs,&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,PetscInt,&rvalues,nrecvs,PetscInt,&source,nrecvs,MPI_Request,&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,PetscInt,&svalues,nsends,MPI_Request,&send_waits,size,PetscInt,&starts);CHKERRQ(ierr); 153 starts[0] = 0; 154 for (i=1; i<size; i++) { starts[i] = starts[i-1] + nprocs[i-1];} 155 for (i=0; i<cnt; i++) { 156 svalues[starts[owner[i]]++] = rows[i]; 157 } 158 for (i=0; i<cnt; i++) rows[i] = rows[i] - rstart; 159 red->drows = drows; 160 red->dcnt = dcnt; 161 ierr = PetscFree(rows);CHKERRQ(ierr); 162 163 starts[0] = 0; 164 for (i=1; i<size; i++) { starts[i] = starts[i-1] + nprocs[i-1];} 165 count = 0; 166 for (i=0; i<size; i++) { 167 if (nprocs[i]) { 168 ierr = MPI_Isend(svalues+starts[i],nprocs[i],MPIU_INT,i,tag,comm,send_waits+count++);CHKERRQ(ierr); 169 } 170 } 171 172 /* wait on receives */ 173 count = nrecvs; 174 slen = 0; 175 while (count) { 176 ierr = MPI_Waitany(nrecvs,recv_waits,&imdex,&recv_status);CHKERRQ(ierr); 177 /* unpack receives into our local space */ 178 ierr = MPI_Get_count(&recv_status,MPIU_INT,&n);CHKERRQ(ierr); 179 slen += n; 180 count--; 181 } 182 if (slen != recvtotal) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Total message lengths %D not expected %D",slen,recvtotal); 183 184 ierr = ISCreateGeneral(comm,slen,rvalues,PETSC_COPY_VALUES,&red->is);CHKERRQ(ierr); 185 186 /* free up all work space */ 187 ierr = PetscFree(olengths1);CHKERRQ(ierr); 188 ierr = PetscFree(onodes1);CHKERRQ(ierr); 189 ierr = PetscFree3(rvalues,source,recv_waits);CHKERRQ(ierr); 190 ierr = PetscFree2(nprocs,owner);CHKERRQ(ierr); 191 if (nsends) { /* wait on sends */ 192 ierr = PetscMalloc(nsends*sizeof(MPI_Status),&send_status);CHKERRQ(ierr); 193 ierr = MPI_Waitall(nsends,send_waits,send_status);CHKERRQ(ierr); 194 ierr = PetscFree(send_status);CHKERRQ(ierr); 195 } 196 ierr = PetscFree3(svalues,send_waits,starts);CHKERRQ(ierr); 197 ierr = PetscLayoutDestroy(&map);CHKERRQ(ierr); 198 ierr = PetscLayoutDestroy(&nmap);CHKERRQ(ierr); 199 200 ierr = VecCreateMPI(comm,slen,PETSC_DETERMINE,&red->b);CHKERRQ(ierr); 201 ierr = VecDuplicate(red->b,&red->x);CHKERRQ(ierr); 202 ierr = MatGetVecs(pc->pmat,&tvec,PETSC_NULL);CHKERRQ(ierr); 203 ierr = VecScatterCreate(tvec,red->is,red->b,PETSC_NULL,&red->scatter);CHKERRQ(ierr); 204 ierr = VecDestroy(&tvec);CHKERRQ(ierr); 205 ierr = MatGetSubMatrix(pc->pmat,red->is,red->is,MAT_INITIAL_MATRIX,&tmat);CHKERRQ(ierr); 206 ierr = KSPSetOperators(red->ksp,tmat,tmat,SAME_NONZERO_PATTERN);CHKERRQ(ierr); 207 ierr = MatDestroy(&tmat);CHKERRQ(ierr); 208 } 209 210 /* get diagonal portion of matrix */ 211 ierr = PetscMalloc(red->dcnt*sizeof(PetscScalar),&red->diag);CHKERRQ(ierr); 212 ierr = MatGetVecs(pc->pmat,&diag,PETSC_NULL);CHKERRQ(ierr); 213 ierr = MatGetDiagonal(pc->pmat,diag);CHKERRQ(ierr); 214 ierr = VecGetArrayRead(diag,&d);CHKERRQ(ierr); 215 for (i=0; i<red->dcnt; i++) { 216 red->diag[i] = 1.0/d[red->drows[i]]; 217 } 218 ierr = VecRestoreArrayRead(diag,&d);CHKERRQ(ierr); 219 ierr = VecDestroy(&diag);CHKERRQ(ierr); 220 ierr = KSPSetUp(red->ksp);CHKERRQ(ierr); 221 PetscFunctionReturn(0); 222 } 223 224 #undef __FUNCT__ 225 #define __FUNCT__ "PCApply_Redistribute" 226 static PetscErrorCode PCApply_Redistribute(PC pc,Vec b,Vec x) 227 { 228 PC_Redistribute *red = (PC_Redistribute*)pc->data; 229 PetscErrorCode ierr; 230 PetscInt dcnt = red->dcnt,i; 231 const PetscInt *drows = red->drows; 232 PetscScalar *xwork; 233 const PetscScalar *bwork,*diag = red->diag; 234 235 PetscFunctionBegin; 236 if (!red->work) { 237 ierr = VecDuplicate(b,&red->work);CHKERRQ(ierr); 238 } 239 /* compute the rows of solution that have diagonal entries only */ 240 ierr = VecSet(x,0.0);CHKERRQ(ierr); /* x = diag(A)^{-1} b */ 241 ierr = VecGetArray(x,&xwork);CHKERRQ(ierr); 242 ierr = VecGetArrayRead(b,&bwork);CHKERRQ(ierr); 243 for (i=0; i<dcnt; i++) { 244 xwork[drows[i]] = diag[i]*bwork[drows[i]]; 245 } 246 ierr = PetscLogFlops(dcnt);CHKERRQ(ierr); 247 ierr = VecRestoreArray(red->work,&xwork);CHKERRQ(ierr); 248 ierr = VecRestoreArrayRead(b,&bwork);CHKERRQ(ierr); 249 /* update the right hand side for the reduced system with diagonal rows (and corresponding columns) removed */ 250 ierr = MatMult(pc->pmat,x,red->work);CHKERRQ(ierr); 251 ierr = VecAYPX(red->work,-1.0,b);CHKERRQ(ierr); /* red->work = b - A x */ 252 253 ierr = VecScatterBegin(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 254 ierr = VecScatterEnd(red->scatter,red->work,red->b,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr); 255 ierr = KSPSolve(red->ksp,red->b,red->x);CHKERRQ(ierr); 256 ierr = VecScatterBegin(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 257 ierr = VecScatterEnd(red->scatter,red->x,x,INSERT_VALUES,SCATTER_REVERSE);CHKERRQ(ierr); 258 PetscFunctionReturn(0); 259 } 260 261 #undef __FUNCT__ 262 #define __FUNCT__ "PCDestroy_Redistribute" 263 static PetscErrorCode PCDestroy_Redistribute(PC pc) 264 { 265 PC_Redistribute *red = (PC_Redistribute*)pc->data; 266 PetscErrorCode ierr; 267 268 PetscFunctionBegin; 269 ierr = VecScatterDestroy(&red->scatter);CHKERRQ(ierr); 270 ierr = ISDestroy(&red->is);CHKERRQ(ierr); 271 ierr = VecDestroy(&red->b);CHKERRQ(ierr); 272 ierr = VecDestroy(&red->x);CHKERRQ(ierr); 273 ierr = KSPDestroy(&red->ksp);CHKERRQ(ierr); 274 ierr = VecDestroy(&red->work);CHKERRQ(ierr); 275 ierr = PetscFree(red->drows); 276 ierr = PetscFree(red->diag); 277 ierr = PetscFree(pc->data);CHKERRQ(ierr); 278 PetscFunctionReturn(0); 279 } 280 281 #undef __FUNCT__ 282 #define __FUNCT__ "PCSetFromOptions_Redistribute" 283 static PetscErrorCode PCSetFromOptions_Redistribute(PC pc) 284 { 285 PetscErrorCode ierr; 286 PC_Redistribute *red = (PC_Redistribute*)pc->data; 287 288 PetscFunctionBegin; 289 ierr = KSPSetFromOptions(red->ksp);CHKERRQ(ierr); 290 PetscFunctionReturn(0); 291 } 292 293 #undef __FUNCT__ 294 #define __FUNCT__ "PCRedistributeGetKSP" 295 /*@ 296 PCRedistributeGetKSP - Gets the KSP created by the PCREDISTRIBUTE 297 298 Not Collective 299 300 Input Parameter: 301 . pc - the preconditioner context 302 303 Output Parameter: 304 . innerksp - the inner KSP 305 306 Level: advanced 307 308 .keywords: PC, redistribute solve 309 @*/ 310 PetscErrorCode PCRedistributeGetKSP(PC pc,KSP *innerksp) 311 { 312 PC_Redistribute *red = (PC_Redistribute*)pc->data; 313 314 PetscFunctionBegin; 315 PetscValidHeaderSpecific(pc,PC_CLASSID,1); 316 PetscValidPointer(innerksp,2); 317 *innerksp = red->ksp; 318 PetscFunctionReturn(0); 319 } 320 321 /* -------------------------------------------------------------------------------------*/ 322 /*MC 323 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 324 325 Options for the redistribute preconditioners can be set with -redistribute_ksp_xxx <values> and -redistribute_pc_xxx <values> 326 327 Notes: Usually run this with -ksp_type preonly 328 329 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 330 -pc_type redistribute -redistribute_ksp_type cg -redistribute_pc_type bjacobi -redistribute_sub_pc_type icc to take advantage of the symmetry. 331 332 Level: intermediate 333 334 .seealso: PCCreate(), PCSetType(), PCType (for list of available types), PCRedistributeGetKSP() 335 M*/ 336 337 EXTERN_C_BEGIN 338 #undef __FUNCT__ 339 #define __FUNCT__ "PCCreate_Redistribute" 340 PetscErrorCode PCCreate_Redistribute(PC pc) 341 { 342 PetscErrorCode ierr; 343 PC_Redistribute *red; 344 const char *prefix; 345 346 PetscFunctionBegin; 347 ierr = PetscNewLog(pc,PC_Redistribute,&red);CHKERRQ(ierr); 348 pc->data = (void*)red; 349 350 pc->ops->apply = PCApply_Redistribute; 351 pc->ops->applytranspose = 0; 352 pc->ops->setup = PCSetUp_Redistribute; 353 pc->ops->destroy = PCDestroy_Redistribute; 354 pc->ops->setfromoptions = PCSetFromOptions_Redistribute; 355 pc->ops->view = PCView_Redistribute; 356 357 ierr = KSPCreate(((PetscObject)pc)->comm,&red->ksp);CHKERRQ(ierr); 358 ierr = PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);CHKERRQ(ierr); 359 ierr = PetscLogObjectParent(pc,red->ksp);CHKERRQ(ierr); 360 ierr = PCGetOptionsPrefix(pc,&prefix);CHKERRQ(ierr); 361 ierr = KSPSetOptionsPrefix(red->ksp,prefix);CHKERRQ(ierr); 362 ierr = KSPAppendOptionsPrefix(red->ksp,"redistribute_");CHKERRQ(ierr); 363 PetscFunctionReturn(0); 364 } 365 EXTERN_C_END 366