Fortran: How to conduct a job repeatedly using multiple files

Question

Project description:

I have the coordinates of McDonalds in cities and the coordinates of city centers. They are divided to text files by city. For example,

 === atlanta_mc.txt ===    === houston_mc.txt ===    ... (for 200 cities)
[latitude]   [longitude]   [latitude] [longitude]    <-- The headers are not written in the files.   
33.5431140  -84.5766910    29.8044570 -95.3990780
34.0489350  -84.0928960    30.0051170 -95.2834550
33.7853660  -84.1018980    29.7371140 -95.5352550   
34.0903210  -84.2040180    29.7280160 -95.4188230 
34.1606520  -84.1781010    29.7851700 -95.3609770
         ....                       ....

My goal is to calculate the distance between the city center and each McDonald for each city. The city center data file has [cityname],[latitude],[longitude] fiels. It looks like:

      == city_centers.txt ==
[city name] [latitude] [longitude] <-- The headers are not written in the file.
atlanta     33.79526   -84.326528 
la          34.057453  -118.413842
ny          40.759347  -73.980202
houston     29.733215  -95.430824
              ....
    (for 200 cities in the US.)

Fortran code:

For one city (say, Atlanta), I can do the job as follows:

program mcdonalds
    implicit none
    interface
        function distkm(deglat1,deglon1,deglat2,deglon2)
        real :: distkm
        real, intent(in) :: deglat1,deglon1,deglat2,deglon2
        end function distkm
    end interface

    integer, parameter :: maxnr = 200
    integer :: nr, i, j, ios
    character(len=1) :: junkfornr
    real, dimension(:), allocatable :: lat, lon

    ! Obtain the total number of observations
    nr=0
    open(10, file='atlanta_mc.txt', status='old')
    do i=1,maxnr
        read(10,*,iostat=ios) junkfornr
        if (ios/=0) exit
        if (i == maxnr) then
        stop
        endif
        nr = nr + 1
    end do

    allocate(lat(nr))
    allocate(lon(nr))

    rewind(10)
    do i=1,nr
    read(10,*) lat(i), lon(i)
    end do

    open(20,file='RESULT_atlanta_mc.txt')

    do i=1,nr
        write(20,100) "atlanta",lat(i),lon(i),distkm(lat(i),lon(i),33.79526,-84.326528)
        100 format(A,3F12.6)
    end do

end program mcdonalds

function distkm(deglat1,deglon1,deglat2,deglon2)
    implicit none 
    real, intent(in) :: deglat1,deglon1,deglat2,deglon2
    real :: pi,dlat,dlon,lat1,lat2,a,distkm
    pi = 4*atan(1.0)
    dlat = (deglat2-deglat1)*pi/180
    dlon = (deglon2-deglon1)*pi/180
    lat1 = deglat1*pi/180
    lat2 = deglat2*pi/180
    a = (sin(dlat/2))**2 + cos(lat1)*cos(lat2)*(sin(dlon/2))**2
    distkm = 6372.8*2*atan2(sqrt(a),sqrt(1-a))
end function distkm

Problem:

I have to do this for the all cities. So, I have to change (1) the McDonalds data file, (2) the city center coordinate; and (3) the result file for each city accordingly. How do I have to write a program to iterate this process for the whole 200 cities? I use Intel Fortran (ifort) to compile it.

EDIT (This code worked -- Friday, April 11, 2014):

! calculate distances from the city center to each McDonald 
! Try this for all the cities
program mcdonalds
    implicit none
    interface
        function distkm(deglat1,deglon1,deglat2,deglon2)
        real :: distkm
        real, intent(in) :: deglat1,deglon1,deglat2,deglon2
        end function distkm
    end interface

    integer, parameter :: maxnr = 200
    integer :: nr, i, j, ios
    character(len=1) :: junkfornr
    character(len=25) :: fn

    real, dimension(:), allocatable :: lat, lon
    real, dimension(5) :: clat, clon
    character(len=15), dimension(5) :: filename
            character(len=6), dimension(5) :: code
    character(len=7), dimension(5) :: cityname

    ! I have a text file that contains the list of data file names, city names and the (lat/lon)s of city centers.
    ! The name of that file: datafilelistcitycenter.txt
    ! === The content of the file looks like: ===
    ! atlanta_mc.txt  11111  atlanta  33.79526   -84.326528
    ! houston_mc.txt  22222  houston  29.733215  -95.430824
    ! la_mc.txt       33333  la       34.057453  -118.413842
    ! ny_mc.txt       44444  ny       40.759347  -73.980202
    ! philly_mc.txt   55555  philly   29.733215  -95.430824

    ! Let's assume we know the number of the cities. 
    ! In this case, it is 5.

    open(10, file='datafilelistcitycenter.txt', status='old')
    rewind(10)
    do i=1,5
        read(10,*) filename(i), cityname(i), clat(i), clon(i)
    end do
    close(10)

    ! Obtain the total number of observations for each city
    do j=1,5

    open(j, file=filename(j), status='old')
    nr=0
    do i=1,maxnr
        read(j,*,iostat=ios) junkfornr
        if (ios/=0) exit
        if (i == maxnr) then
            write(*,*) "Error: Maximum number of records exceeded..."
            write(*,*) "Exiting the program..."
            stop
        endif
        nr = nr + 1
    end do

    allocate(lat(nr),lon(nr))

    rewind(j)
    do i=1,nr
        read(j,*) lat(i), lon(i)
    end do
    close(j)

    write(fn, '("RESULT_",A15)') filename(j)
    open(j,file=fn)

    do i=1,nr
        write(j,100) code(j),cityname(j),lat(i),lon(i),distkm(lat(i),lon(i),clat(j),clon(j))
        100 format(A6,A7,3F12.6)
    end do
    close(j)

    deallocate(lat,lon)

    end do

end program mcdonalds

function distkm(deglat1,deglon1,deglat2,deglon2)
    implicit none 
    real, intent(in) :: deglat1,deglon1,deglat2,deglon2
    real :: pi,dlat,dlon,lat1,lat2,a,distkm
    pi = 4*atan(1.0)
    dlat = (deglat2-deglat1)*pi/180
    dlon = (deglon2-deglon1)*pi/180
    lat1 = deglat1*pi/180
    lat2 = deglat2*pi/180
    a = (sin(dlat/2))**2 + cos(lat1)*cos(lat2)*(sin(dlon/2))**2
    distkm = 6372.8*2*atan2(sqrt(a),sqrt(1-a))
end function distkm

No luck. I end up with very weird messages: severe <66>: output statement overflows record, unit -5, file Internal Fomatted Write.

EDIT: I think I got it right. Thanks.

Fortran: How to conduct a job repeatedly using multiple files

Answers (1)

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