| 1 | = Ex3.f90 = |

| 2 | {{{#!fortran |

| 3 | ! |

| 4 | ! Large Scale Computing |

| 5 | ! Heat/Mass Transfer |

| 6 | ! ex3.f90 |

| 7 | ! |

| 8 | program diffusion1d |

| 9 | implicit none |

| 10 | double precision :: a,b,d |

| 11 | double precision,dimension(:),allocatable :: phi,phi0 |

| 12 | double precision,dimension(:),allocatable :: rhs |

| 13 | double precision :: dx |

| 14 | double precision :: err,merr |

| 15 | double precision,parameter :: tol = 1.0e-8 |

| 16 | integer :: i,num,itc |

| 17 | |

| 18 | character(len=32) :: arg |

| 19 | |

| 20 | ! Newer version of Fortran can get commadline arguments |

| 21 | do i=1,4 |

| 22 | call get_command_argument(i,arg) |

| 23 | if (len_trim(arg) == 0) then |

| 24 | call get_command_argument(0,arg) |

| 25 | print *,arg," [num] [A] [B] [D]" |

| 26 | call exit(-1) |

| 27 | end if |

| 28 | |

| 29 | ! get inputed depth |

| 30 | if (i == 1) read(arg,*) num |

| 31 | if (i == 2) read(arg,*) a |

| 32 | if (i == 3) read(arg,*) b |

| 33 | if (i == 4) read(arg,*) d |

| 34 | end do |

| 35 | |

| 36 | print *,"num=",num,"A=",a,"B=",b,"D=",d |

| 37 | |

| 38 | ! Memory Allocation |

| 39 | allocate(phi(num)) |

| 40 | allocate(phi0(num)) |

| 41 | allocate(rhs(num)) |

| 42 | |

| 43 | ! Setup |

| 44 | dx = 1.d0 / dble(num - 1) |

| 45 | do i = 1,num |

| 46 | rhs(i) = -dx * dx / d * (dx * dble(i)) |

| 47 | phi(i) = 0.d0 |

| 48 | phi0(i) = 0.d0 |

| 49 | end do |

| 50 | |

| 51 | ! Boundary Condition |

| 52 | phi(1) = a |

| 53 | phi0(1) = a |

| 54 | phi(num) = b |

| 55 | phi0(num) = b |

| 56 | |

| 57 | ! Solve with Jacobi Method |

| 58 | itc = 0; |

| 59 | do |

| 60 | ! update phi |

| 61 | do i = 2,num-1 |

| 62 | phi(i) = -0.5 * (rhs(i) - phi0(i + 1) - phi0(i - 1)) |

| 63 | end do |

| 64 | |

| 65 | ! Check Convergence |

| 66 | merr = 0.d0 |

| 67 | do i = 1, num |

| 68 | err = abs(phi(i) - phi0(i)) |

| 69 | if (merr < err) then |

| 70 | merr = err |

| 71 | end if |

| 72 | phi0(i) = phi(i) |

| 73 | end do |

| 74 | |

| 75 | itc = itc + 1 |

| 76 | if (merr < tol) exit |

| 77 | if (mod(itc,10000) == 0) print *,"itc=",itc,"err=",merr |

| 78 | end do |

| 79 | |

| 80 | print *,"Number of Iteration=",itc |

| 81 | |

| 82 | ! Output Result |

| 83 | open(10,FILE='res.dat') |

| 84 | do i = 1,num |

| 85 | write(10,'(2e16.8)') dx * dble(i-1),phi(i) |

| 86 | end do |

| 87 | close(10) |

| 88 | |

| 89 | ! END : Deallocate Memory |

| 90 | deallocate(phi) |

| 91 | deallocate(phi0) |

| 92 | deallocate(rhs) |

| 93 | print *,"Done" |

| 94 | end program diffusion1d |

| 95 | }}} |