Actual source code: ex88f.F90

  1: !
  2: !     Creates a tridiagonal sparse matrix explicitly in Fortran and solves a linear system with it
  3: !
  4: !     The matrix is provided in triples in a way that supports new nonzero values with the same nonzero structure
  5: !
  6:       program main
  7: #include <petsc/finclude/petscksp.h>
  8:       use petscksp
  9:       implicit none

 11:       PetscInt i,n,nz
 12:       PetscBool flg
 13:       PetscErrorCode ierr
 14:       PetscScalar,ALLOCATABLE :: a(:)
 15:       PetscScalar,pointer :: b(:)

 17:       PetscInt,ALLOCATABLE :: rows(:)
 18:       PetscInt,ALLOCATABLE :: cols(:)

 20:       Mat J
 21:       Vec rhs,solution
 22:       KSP ksp

 24:       PetscCallA(PetscInitialize(ierr))

 26:       n = 3
 27:       PetscCallA(PetscOptionsGetInt(PETSC_NULL_OPTIONS,PETSC_NULL_CHARACTER,'-n',n,flg,ierr))
 28:       nz = 3*n - 4;

 30:       PetscCallA(VecCreateSeq(PETSC_COMM_SELF,n,rhs,ierr))
 31:       PetscCallA(VecCreateSeq(PETSC_COMM_SELF,n,solution,ierr))
 32:       ALLOCATE (rows(nz),cols(nz),a(nz))

 34:       PetscCallA(VecGetArrayF90(rhs,b,ierr))
 35:       do i=1,n
 36:         b(i) = 1.0
 37:       enddo
 38:       PetscCallA(VecRestoreArrayF90(rhs,b,ierr))

 40:       rows(1) = 0; cols(1) = 0
 41:       a(1)  = 1.0
 42:       do i=2,n-1
 43:          rows(2+3*(i-2)) = i-1; cols(2+3*(i-2)) = i-2
 44:          a(2+3*(i-2))    = -1.0;
 45:          rows(2+3*(i-2)+1) = i-1; cols(2+3*(i-2)+1) = i-1
 46:          a(2+3*(i-2)+1)  = 2.0;
 47:          rows(2+3*(i-2)+2) = i-1; cols(2+3*(i-2)+2) = i
 48:          a(2+3*(i-2)+2)  = -1.0;
 49:       enddo
 50:       rows(nz) = n-1; cols(nz) = n-1
 51:       a(nz) = 1.0

 53:       PetscCallA(MatCreate(PETSC_COMM_SELF,J,ierr))
 54:       PetscCallA(MatSetSizes(J,n,n,n,n,ierr))
 55:       PetscCallA(MatSetType(J,MATSEQAIJ,ierr))
 56:       PetscCallA(MatSetPreallocationCOO(J,nz,rows,cols,ierr))
 57:       PetscCallA(MatSetValuesCOO(J,a,INSERT_VALUES,ierr))

 59:       PetscCallA(KSPCreate(PETSC_COMM_SELF,ksp,ierr))
 60:       PetscCallA(KSPSetErrorIfNotConverged(ksp,PETSC_TRUE,ierr))
 61:       PetscCallA(KSPSetFromOptions(ksp,ierr))
 62:       PetscCallA(KSPSetOperators(ksp,J,J,ierr))

 64:       PetscCallA(KSPSolve(ksp,rhs,solution,ierr))

 66: !     Keep the same size and nonzero structure of the matrix but change its numerical entries
 67:       do i=2,n-1
 68:          a(2+3*(i-2)+1)  = 4.0;
 69:       enddo
 70:       PetscCallA(MatSetValuesCOO(J,a,INSERT_VALUES,ierr))

 72:       PetscCallA(KSPSolve(ksp,rhs,solution,ierr))

 74:       PetscCallA(KSPDestroy(ksp,ierr))
 75:       PetscCallA(VecDestroy(rhs,ierr))
 76:       PetscCallA(VecDestroy(solution,ierr))
 77:       PetscCallA(MatDestroy(J,ierr))

 79:       DEALLOCATE (rows, cols, a)

 81:       PetscCallA(PetscFinalize(ierr))
 82:       end

 84: !/*TEST
 85: !
 86: !     test:
 87: !       requires: defined(PETSC_USE_SINGLE_LIBRARY)
 88: !       nsize: 3
 89: !       filter: sed 's?ATOL?RTOL?g' | grep -v HERMITIAN | grep -v "shared memory" | grep -v "Mat_0"
 90: !       # use the MPI Linear Solver Server
 91: !       args: -n 20 -mpi_linear_solver_server -mpi_linear_solver_server_view -mpi_linear_solver_server_use_shared_memory false
 92: !       # controls for the use of PCMPI on a particular system
 93: !       args: -mpi_linear_solver_server_minimum_count_per_rank 5 -mpi_linear_solver_server_ksp_view
 94: !       # the usual options for the linear solver (in this case using the server)
 95: !       args: -ksp_monitor -ksp_converged_reason -ksp_view
 96: !
 97: !     test:
 98: !       suffix: 2
 99: !       requires: defined(PETSC_USE_SINGLE_LIBRARY)
100: !       nsize: 3
101: !       filter: sed 's?ATOL?RTOL?g' | grep -v HERMITIAN | grep -v "shared memory" | grep -v "Mat_0"
102: !       # use the MPI Linear Solver Server
103: !       args: -n 20 -mpi_linear_solver_server -mpi_linear_solver_server_view -mpi_linear_solver_server_use_shared_memory false
104: !       # controls for the use of PCMPI on a particular system
105: !       args: -mpi_linear_solver_server_ksp_view
106: !       # the usual options for the linear solver (in this case using the server)
107: !       args: -ksp_monitor -ksp_converged_reason -ksp_view
108: !
109: !TEST*/