1 2 static char help[] = "Test PC redistribute on matrix with load imbalance. \n\ 3 Modified from src/ksp/ksp/tutorials/ex2.c.\n\ 4 Input parameters include:\n\ 5 -random_exact_sol : use a random exact solution vector\n\ 6 -view_exact_sol : write exact solution vector to stdout\n\ 7 -n <mesh_y> : number of mesh points\n\n"; 8 /* 9 Example: 10 mpiexec -n 8 ./ex3 -n 10000 -ksp_type cg -pc_type bjacobi -sub_pc_type icc -ksp_rtol 1.e-8 -log_view 11 mpiexec -n 8 ./ex3 -n 10000 -ksp_type preonly -pc_type redistribute -redistribute_ksp_type cg -redistribute_pc_type bjacobi -redistribute_sub_pc_type icc -redistribute_ksp_rtol 1.e-8 -log_view 12 */ 13 14 #include <petscksp.h> 15 16 int main(int argc,char **args) 17 { 18 Vec x,b,u; /* approx solution, RHS, exact solution */ 19 Mat A; /* linear system matrix */ 20 KSP ksp; /* linear solver context */ 21 PetscRandom rctx; /* random number generator context */ 22 PetscReal norm; /* norm of solution error */ 23 PetscInt i,j,Ii,J,Istart,Iend,m,n = 7,its,nloc,matdistribute=0; 24 PetscErrorCode ierr; 25 PetscBool flg = PETSC_FALSE; 26 PetscScalar v; 27 PetscMPIInt rank,size; 28 #if defined(PETSC_USE_LOG) 29 PetscLogStage stage; 30 #endif 31 32 CHKERRQ(PetscInitialize(&argc,&args,(char*)0,help)); 33 CHKERRMPI(MPI_Comm_size(PETSC_COMM_WORLD,&size)); 34 CHKERRMPI(MPI_Comm_rank(PETSC_COMM_WORLD,&rank)); 35 PetscCheckFalse(size < 2,PETSC_COMM_WORLD,PETSC_ERR_WRONG_MPI_SIZE,"This example requires at least 2 MPI processes!"); 36 37 CHKERRQ(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL)); 38 CHKERRQ(PetscOptionsGetInt(NULL,NULL,"-matdistribute",&matdistribute,NULL)); 39 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 40 Compute the matrix and right-hand-side vector that define 41 the linear system, Ax = b. 42 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 43 switch(matdistribute) { 44 case 1: /* very imbalanced process load for matrix A */ 45 m = (1+size)*size; 46 nloc = (rank+1)*n; 47 if (rank == size-1) { /* proc[size-1] stores all remaining rows */ 48 nloc = m*n; 49 for (i=0; i<size-1; i++) { 50 nloc -= (i+1)*n; 51 } 52 } 53 break; 54 default: /* proc[0] and proc[1] load much smaller row blocks, the rest processes have same loads */ 55 if (rank == 0 || rank == 1) { 56 nloc = n; 57 } else { 58 nloc = 10*n; /* 10x larger load */ 59 } 60 m = 2 + (size-2)*10; 61 break; 62 } 63 CHKERRQ(MatCreate(PETSC_COMM_WORLD,&A)); 64 CHKERRQ(MatSetSizes(A,nloc,nloc,PETSC_DECIDE,PETSC_DECIDE)); 65 CHKERRQ(MatSetFromOptions(A)); 66 CHKERRQ(MatMPIAIJSetPreallocation(A,5,NULL,5,NULL)); 67 CHKERRQ(MatSeqAIJSetPreallocation(A,5,NULL)); 68 CHKERRQ(MatSetUp(A)); 69 70 CHKERRQ(MatGetOwnershipRange(A,&Istart,&Iend)); 71 nloc = Iend-Istart; 72 CHKERRQ(PetscSynchronizedPrintf(PETSC_COMM_WORLD,"[%d] A Istart,Iend: %D %D; nloc %D\n",rank,Istart,Iend,nloc)); 73 CHKERRQ(PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT)); 74 75 CHKERRQ(PetscLogStageRegister("Assembly", &stage)); 76 CHKERRQ(PetscLogStagePush(stage)); 77 for (Ii=Istart; Ii<Iend; Ii++) { 78 v = -1.0; i = Ii/n; j = Ii - i*n; 79 if (i>0) {J = Ii - n; CHKERRQ(MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES));} 80 if (i<m-1) {J = Ii + n; CHKERRQ(MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES));} 81 if (j>0) {J = Ii - 1; CHKERRQ(MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES));} 82 if (j<n-1) {J = Ii + 1; CHKERRQ(MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES));} 83 v = 4.0; CHKERRQ(MatSetValues(A,1,&Ii,1,&Ii,&v,INSERT_VALUES)); 84 } 85 CHKERRQ(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY)); 86 CHKERRQ(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY)); 87 CHKERRQ(PetscLogStagePop()); 88 89 /* A is symmetric. Set symmetric flag to enable ICC/Cholesky preconditioner */ 90 CHKERRQ(MatSetOption(A,MAT_SYMMETRIC,PETSC_TRUE)); 91 92 /* Create parallel vectors. */ 93 CHKERRQ(VecCreate(PETSC_COMM_WORLD,&u)); 94 CHKERRQ(VecSetSizes(u,nloc,PETSC_DECIDE)); 95 CHKERRQ(VecSetFromOptions(u)); 96 CHKERRQ(VecDuplicate(u,&b)); 97 CHKERRQ(VecDuplicate(b,&x)); 98 99 /* Set exact solution; then compute right-hand-side vector. */ 100 CHKERRQ(PetscOptionsGetBool(NULL,NULL,"-random_exact_sol",&flg,NULL)); 101 if (flg) { 102 CHKERRQ(PetscRandomCreate(PETSC_COMM_WORLD,&rctx)); 103 CHKERRQ(PetscRandomSetFromOptions(rctx)); 104 CHKERRQ(VecSetRandom(u,rctx)); 105 CHKERRQ(PetscRandomDestroy(&rctx)); 106 } else { 107 CHKERRQ(VecSet(u,1.0)); 108 } 109 CHKERRQ(MatMult(A,u,b)); 110 111 /* View the exact solution vector if desired */ 112 flg = PETSC_FALSE; 113 CHKERRQ(PetscOptionsGetBool(NULL,NULL,"-view_exact_sol",&flg,NULL)); 114 if (flg) CHKERRQ(VecView(u,PETSC_VIEWER_STDOUT_WORLD)); 115 116 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 117 Create the linear solver and set various options 118 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 119 CHKERRQ(KSPCreate(PETSC_COMM_WORLD,&ksp)); 120 CHKERRQ(KSPSetOperators(ksp,A,A)); 121 ierr = KSPSetTolerances(ksp,1.e-2/((m+1)*(n+1)),PETSC_DEFAULT,PETSC_DEFAULT, 122 PETSC_DEFAULT);CHKERRQ(ierr); 123 CHKERRQ(KSPSetFromOptions(ksp)); 124 125 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 126 Solve the linear system 127 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 128 CHKERRQ(KSPSolve(ksp,b,x)); 129 130 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 131 Check solution and clean up 132 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 133 CHKERRQ(VecAXPY(x,-1.0,u)); 134 CHKERRQ(VecNorm(x,NORM_2,&norm)); 135 CHKERRQ(KSPGetIterationNumber(ksp,&its)); 136 CHKERRQ(PetscPrintf(PETSC_COMM_WORLD,"Norm of error %g iterations %D\n",(double)norm,its)); 137 138 /* Free work space. */ 139 CHKERRQ(KSPDestroy(&ksp)); 140 CHKERRQ(VecDestroy(&u)); CHKERRQ(VecDestroy(&x)); 141 CHKERRQ(VecDestroy(&b)); CHKERRQ(MatDestroy(&A)); 142 CHKERRQ(PetscFinalize()); 143 return 0; 144 } 145 146 /*TEST 147 148 test: 149 nsize: 8 150 args: -n 100 -ksp_type cg -pc_type bjacobi -sub_pc_type icc -ksp_rtol 1.e-8 151 152 test: 153 suffix: 2 154 nsize: 8 155 args: -n 100 -ksp_type preonly -pc_type redistribute -redistribute_ksp_type cg -redistribute_pc_type bjacobi -redistribute_sub_pc_type icc -redistribute_ksp_rtol 1.e-8 156 157 TEST*/ 158