fatal error : can't open module file 'mainmodule.mod'

!=============================================================================== ! Global module !=============================================================================== module Globals real(8), allocatable, save :: u(:), flux(:)

integer, save :: cells, ntmaxi

real(8), save :: cflcoe, domlen, dt, timeout, timeto, dx

end module Globals

!=============================================================================== ! Main module !=============================================================================== module MainModule use Globals implicit none

contains

!---------------------------------------------------------------------------- ! Purpose: to read initial parameters of the problem !---------------------------------------------------------------------------- subroutine reader open(unit=1, file='b1god.ini', status='unknown')

   read(1, *)cflcoe
   read(1, *)domlen
   read(1, *)cells
   read(1, *)ntmaxi
   read(1, *)timeout

   close(1)

   write(*, *)
   write(*, *)'Input data echoed to screen'
   write(*, *)
   write(*, *)'cflcoe  =', cflcoe
   write(*, *)'domlen  =', domlen
   write(*, *)'cells   =', cells
   write(*, *)'ntmaxi  =', ntmaxi
   write(*, *)'timeout =', timeout
end subroutine reader

!---------------------------------------------------------------------------
! Purpose: to set initial conditions for solution U
!           and initialise other variables
!---------------------------------------------------------------------------
subroutine initia(domlen, cells)
   real(8), intent(in) :: domlen
   integer, intent(in) :: cells

   integer i
   real(8) xleft, xpos, xmiddle, xright

   allocate(flux(0 : cells+1))
   allocate(u   (0 : cells+1))

   dx = domlen/real(cells)
   do i = 0, cells + 1
      flux(i) = 0.0
      u (i)   = 0.0
   end do

   xleft  = 0.3*domlen
   xright = 0.7*domlen
   do i = 1, cells
      xpos = (real(i)-1.0)*dx
      if(xpos < xleft) then
         u(i) = -0.5
      else if(xleft <= xpos .and. xpos <=xright) then
         u(i) = 1.0
      else
         u(i) = 0
      endif
    end do
end subroutine initia

!---------------------------------------------------------------------------
! Purpose: to apply boundary conditions
!---------------------------------------------------------------------------
subroutine bcondi(cells)
   integer, intent (in) :: cells

   u(0) = u(1)

   u(cells + 1) = u(cells)
end subroutine bcondi

!---------------------------------------------------------------------------
! Purpose: to apply the CFL condition to compute a stable time step DT
!---------------------------------------------------------------------------
subroutine cflcon(cflcoe, cells, time, timeout)
   real(8), intent(in) :: cflcoe, time, timeout
   integer, intent(in) :: cells
   real(8) smax
   integer i
   smax = -1.0e+06

   do i = 0, cells + 1
      if(abs(u(i)) >= smax) smax = abs(u(i))
   end do

   dt = cflcoe*dx/smax       ! Choosing the time step

   if(time + dt> timeout) then
      dt = timeout - time
   endif
end subroutine cflcon

!---------------------------------------------------------------------------
! Purpose: to update the solution to a new time level
!        @using the explicit conservative formula
!---------------------------------------------------------------------------
subroutine update(cells)
   integer, intent(in) :: cells
   real(8) dtodx
   integer i

   dtodx = dt / dx

   do i = 1, cells
      u(i) = u(i) + dtodx*(flux(i-1) - flux(i))   !(2.29)
   end do

end subroutine update

!---------------------------------------------------------------------------
! Purpose: to output the solution at a specified time TIMEOUT
!---------------------------------------------------------------------------
subroutine output(cells)
   integer, intent(in) :: cells

   integer i
   real(8) xpos
   open(unit = 1, file = 'numerical.out', status = 'unknown')

   do i = 1, cells
      xpos = real(i)*dx
      write(1,'(f14.6, 2x, f14.6)')xpos, u(i)
   end do

   close(1)
end subroutine output

!---------------------------------------------------------------------------
! Purpose: to compute intercell fluxes according to the
!          Godunov first-order upwind method, inconjunction with
!          the exact Riemann solver
!---------------------------------------------------------------------------
subroutine fluxes(cells)
   integer, intent(in) :: cells

   integer i
   real(8) ul, ur, ustar

   do i = 0, cells
      ul = u(i)
      ur = u(i+1)

      call riemann(ul, ur, ustar)

      flux(i) = 0.5*ustar*ustar    !flux for Burgers equation
   end do
end subroutine fluxes

!---------------------------------------------------------------------------
! Purpose: to solve the Riemann problem for the inviscid Burgers
!          equation exactly
!---------------------------------------------------------------------------
subroutine riemann(ul, ur, ustar)
   real(8), intent(in) :: ul, ur
   real(8), intent(out):: ustar

   real(8)s

   if(ul > ur) then
      s=0.5* (ul+ur)

      if(s>0) then
        ustar =ul
      else
        ustar =ur

end subroutine riemann

end module MainModule

!=============================================================================== ! Main program !=============================================================================== program main use Globals use MainModule

implicit none

integer n real(8) time

time = 0.0

! Parameters of problem are read in from file 'b1god.ini' call reader

! Initial conditions are set up call initia(domlen, cells) write(*, )' ' write(, )'---------------------------------------------' write(, )' Time step N Time ' write(, *)'---------------------------------------------'

! Time marching procedure do n = 1, ntmaxi write(,) n, time

  ! Boundary conditions are set
  call bcondi (cells)

  ! Courant-Friedrichs-Lewy (CFL) condition imposed
  call cflcon(cflcoe, cells, time, timeout)
  time = time + dt

  ! Intercell numerical fluxes are computed
  call fluxes(cells)

  ! Solution is updated according to conservation formula
  call update(cells)

  ! Check output time
  if(abs(time - timeout) <= timeto) then

     ! Solution is written to \'numerical.out\'
     ! at specified time TIMEOUT
     call output(cells)

     write(*, *)'-------------------------------------------'
     write(*, *)'      Number of time steps =',n
     write(*, *)'-------------------------------------------'
     exit
  endif
end do

end program main

why fail to compile with fatal error? compile online in https://www.tutorialspoint.com/compile_fortran_online.php

Can you post it without smilies.

The smilies are automatically generated by phpbb. I think, the easiest or may be only way to avoid this is to mark the text and use the 'Code' button. Example:

real(8), allocatable, save :: u(:), flux(:)

Without this, the same text is displayed like this:

real(8), allocatable, save :: u(:), flux(:)

Wilfried

I just found another way: After writing the post and before sending it, activate the option 'Disable Smilies in this post'. Same text as before:

real(8), allocatable, save :: u(:), flux(:)

this is the complete file, when compiling there is some errors and fatal error for mainmodule.mod no such fill.

https://www.dropbox.com/s/13u3n43fpc5xrnr/Global%20module.txt?dl=0

Please help me to solve it?

Change the name of the file from 'Global Module.txt' to, say, b1god.f90. There seem to be two lines containing 'ENDIF' that should have been present after line 185 but are lost.

As you were advised earlier, use a unit number such as 11 instead of 1 for the input and output files.

After you make these changes, make sure that you have the data file b1god.ini in the same directory. You can compile and link the program with the command

ftn95 b1god.f90 /link 

Agree with all comments. Just will add that specifically for novices and generally for anyone is better to use these commands so that you will understand what the code is doing in real time

ftn95 b1god.f90 /link /checkmate >zzz 

where zzz will be compiler generated file containing errors, comments and warnings. And the /checkmate (same as /undef) is one very nice debugging option, do not use it when the code will be completely error-free as it slows down the execution.

Then if b1god.EXE file will be created run it via debugger

sdbg b1god.exe

and hitting F7 see step by step execution of your program. Other debugger's commands are in the menu and are are completely self-explanatory to anyone including your dogs and cats (most of computer games children play today are infinitely more complex and no one ever RTFM)

What specifically is the data in the initial data file b1god.ini ?

Quoted from DanRRight What specifically is the data in the initial data file b1god.ini ?

The file is in the Zip file to which a link was posted in https://forums.silverfrost.com/Forum/Topic/3121 . It contains five lines of input data for the program:

0.8
1.5
75
100
0.5

Running with /checkmate reveals a bug in the program: Subroutine Riemann leaves ustar undefined if ul ⇐ ur .