1 2 static char help[] = "Tests PC and KSP on a tridiagonal matrix. Note that most\n\ 3 users should employ the KSP interface instead of using PC directly.\n\n"; 4 5 #include <petscksp.h> 6 7 int main(int argc,char **args) 8 { 9 Mat mat; /* matrix */ 10 Vec b,ustar,u; /* vectors (RHS, exact solution, approx solution) */ 11 PC pc; /* PC context */ 12 KSP ksp; /* KSP context */ 13 PetscErrorCode ierr; 14 PetscInt n = 10,i,its,col[3]; 15 PetscScalar value[3]; 16 PCType pcname; 17 KSPType kspname; 18 PetscReal norm,tol=1000.*PETSC_MACHINE_EPSILON; 19 20 ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr; 21 /* Create and initialize vectors */ 22 ierr = VecCreateSeq(PETSC_COMM_SELF,n,&b);CHKERRQ(ierr); 23 ierr = VecCreateSeq(PETSC_COMM_SELF,n,&ustar);CHKERRQ(ierr); 24 ierr = VecCreateSeq(PETSC_COMM_SELF,n,&u);CHKERRQ(ierr); 25 ierr = VecSet(ustar,1.0);CHKERRQ(ierr); 26 ierr = VecSet(u,0.0);CHKERRQ(ierr); 27 28 /* Create and assemble matrix */ 29 ierr = MatCreateSeqAIJ(PETSC_COMM_SELF,n,n,3,NULL,&mat);CHKERRQ(ierr); 30 value[0] = -1.0; value[1] = 2.0; value[2] = -1.0; 31 for (i=1; i<n-1; i++) { 32 col[0] = i-1; col[1] = i; col[2] = i+1; 33 ierr = MatSetValues(mat,1,&i,3,col,value,INSERT_VALUES);CHKERRQ(ierr); 34 } 35 i = n - 1; col[0] = n - 2; col[1] = n - 1; 36 ierr = MatSetValues(mat,1,&i,2,col,value,INSERT_VALUES);CHKERRQ(ierr); 37 i = 0; col[0] = 0; col[1] = 1; value[0] = 2.0; value[1] = -1.0; 38 ierr = MatSetValues(mat,1,&i,2,col,value,INSERT_VALUES);CHKERRQ(ierr); 39 ierr = MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); 40 ierr = MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); 41 42 /* Compute right-hand-side vector */ 43 ierr = MatMult(mat,ustar,b);CHKERRQ(ierr); 44 45 /* Create PC context and set up data structures */ 46 ierr = PCCreate(PETSC_COMM_WORLD,&pc);CHKERRQ(ierr); 47 ierr = PCSetType(pc,PCNONE);CHKERRQ(ierr); 48 ierr = PCSetFromOptions(pc);CHKERRQ(ierr); 49 ierr = PCSetOperators(pc,mat,mat);CHKERRQ(ierr); 50 ierr = PCSetUp(pc);CHKERRQ(ierr); 51 52 /* Create KSP context and set up data structures */ 53 ierr = KSPCreate(PETSC_COMM_WORLD,&ksp);CHKERRQ(ierr); 54 ierr = KSPSetType(ksp,KSPRICHARDSON);CHKERRQ(ierr); 55 ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr); 56 ierr = PCSetOperators(pc,mat,mat);CHKERRQ(ierr); 57 ierr = KSPSetPC(ksp,pc);CHKERRQ(ierr); 58 ierr = KSPSetUp(ksp);CHKERRQ(ierr); 59 60 /* Solve the problem */ 61 ierr = KSPGetType(ksp,&kspname);CHKERRQ(ierr); 62 ierr = PCGetType(pc,&pcname);CHKERRQ(ierr); 63 ierr = PetscPrintf(PETSC_COMM_SELF,"Running %s with %s preconditioning\n",kspname,pcname);CHKERRQ(ierr); 64 ierr = KSPSolve(ksp,b,u);CHKERRQ(ierr); 65 ierr = VecAXPY(u,-1.0,ustar);CHKERRQ(ierr); 66 ierr = VecNorm(u,NORM_2,&norm);CHKERRQ(ierr); 67 ierr = KSPGetIterationNumber(ksp,&its);CHKERRQ(ierr); 68 if (norm > tol) { 69 ierr = PetscPrintf(PETSC_COMM_SELF,"2 norm of error %g Number of iterations %D\n",(double)norm,its);CHKERRQ(ierr); 70 } 71 72 /* Free data structures */ 73 ierr = KSPDestroy(&ksp);CHKERRQ(ierr); 74 ierr = VecDestroy(&u);CHKERRQ(ierr); 75 ierr = VecDestroy(&ustar);CHKERRQ(ierr); 76 ierr = VecDestroy(&b);CHKERRQ(ierr); 77 ierr = MatDestroy(&mat);CHKERRQ(ierr); 78 ierr = PCDestroy(&pc);CHKERRQ(ierr); 79 80 ierr = PetscFinalize(); 81 return ierr; 82 } 83 84 /*TEST 85 86 test: 87 args: -ksp_type cg -ksp_monitor_short 88 89 TEST*/ 90