Fortran：如何使用多个文件重复执行作业

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.

Answer 1

Instead of opening one specific city file such as atlanta_mc.tx, create a file that a list of the filenames of the city. Open that file, add a new loop to your program and read a name of a city file, open and process it as you do now, then close the file. Next iteration of new loop will process the next city file, etc. This is assuming that the cities are in separate files. If they are in one big file, then create arrays to hold information for all of the cities, read all the information into the array, then have a new loop to iterate over the cities.

Also, if you place your function distkm into a module you won't have to bother with having an interface for it. Using modules and easier and less error prone. An example: distkm