4   -l N              Use N Levels.  \n\
31   PetscInt    x_mesh = 15, levels = 3, cycles = 1, use_jacobi = 0;  in main()  local
44   PetscCall(PetscOptionsGetInt(NULL, NULL, "-l", &levels, NULL));  in main()
55   PetscCall(PetscMalloc1(levels, &N));  in main()
57   for (i = 1; i < levels; i++) {  in main()
59 …PetscCheck(N[i] >= 1, PETSC_COMM_WORLD, PETSC_ERR_USER, "Too many levels or N is not large enough"…  in main()
62   PetscCall(Create1dLaplacian(N[levels - 1], &cmat));  in main()
68   PetscCall(PCMGSetLevels(pcmg, levels, NULL));  in main()
78   for (i = 0; i < levels - 1; i++) {  in main()
81     PetscCall(PCMGSetResidual(pcmg, levels - 1 - i, residual, NULL));  in main()
85     PetscCall(PCMGSetInterpolation(pcmg, levels - 1 - i, mat[i]));  in main()
86     PetscCall(PCMGSetRestriction(pcmg, levels - 1 - i, mat[i]));  in main()
87     PetscCall(PCMGSetCycleTypeOnLevel(pcmg, levels - 1 - i, (PCMGCycleType)cycles));  in main()
90     PetscCall(PCMGGetSmoother(pcmg, levels - 1 - i, &ksp[i]));  in main()
117     X[levels - 1 - i] = x;  in main()
118     if (i > 0) PetscCall(PCMGSetX(pcmg, levels - 1 - i, x));  in main()
121     B[levels - 1 - i] = x;  in main()
122     if (i > 0) PetscCall(PCMGSetRhs(pcmg, levels - 1 - i, x));  in main()
125     R[levels - 1 - i] = x;  in main()
127     PetscCall(PCMGSetR(pcmg, levels - 1 - i, x));  in main()
130   PetscCall(VecCreateSeq(PETSC_COMM_SELF, N[levels - 1], &x));  in main()
133   PetscCall(VecCreateSeq(PETSC_COMM_SELF, N[levels - 1], &x));  in main()
143   PetscCall(CalculateRhs(B[levels - 1]));  in main()
144   PetscCall(VecSet(X[levels - 1], 0.0));  in main()
146   PetscCall(residual((Mat)0, B[levels - 1], X[levels - 1], R[levels - 1]));  in main()
147   PetscCall(CalculateError(solution, X[levels - 1], R[levels - 1], e));  in main()
150   PetscCall(KSPSolve(kspmg, B[levels - 1], X[levels - 1]));  in main()
152   PetscCall(residual((Mat)0, B[levels - 1], X[levels - 1], R[levels - 1]));  in main()
153   PetscCall(CalculateError(solution, X[levels - 1], R[levels - 1], e));  in main()
161   for (i = 0; i < levels; i++) {  in main()
166   for (i = 0; i < levels - 1; i++) PetscCall(MatDestroy(&mat[i]));  in main()