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Reading a two-dimensional array in namelist, f90

  1. Apr 28, 2012 #1
    I'd like to create some test data to read 2-dim arrays in f90 with namelists. Suppose I have this in the main program:

    integer, dimension(2,3) array_in, array_out
    namelist /WW_ARRAY/ array_in, array_out
    Open(unit=WW_ARRAY_infile, file="WW_ARRAY_in.dat", status = "OLD")

    ww_array_in.dat might look like this:

    array_in(1:1) = 1,
    array_in(1:2) = 2,
    array_in(2:1) = 3,
    array_in(2:2) = 4

    but maybe there's any easier way to write this?
  2. jcsd
  3. Apr 30, 2012 #2
    What language is this?
  4. Apr 30, 2012 #3


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    Science Advisor
    Homework Helper

    If you don't know, you are not a http://en.wikipedia.org/wiki/Real_Programmer :smile:

    I can't answer the OP's question, but I would expect you can input the array column by column just as a list of numbers, without all the "array_in(1:1)" stuff. It's "read the manual" time...
  5. Apr 30, 2012 #4
    This does a better job of illustrating what happens by looking what a program can output for a 2-d array.

    ! write/read array data
    integer :: n=1
    real :: delta = 0.12

    real, dimension(1:5, 1:2) :: astro_data
    namelist /astro_nml/ astro_data, a, b, c
    real :: a, b
    character*12 :: c
    integer :: astro_file = 10

    ! generate astro_nml values
    c="just c"

    do j = 1,5
    do k = 1,2
    astro_data(j,k) = j*1.0 + (k-1)*delta
    end do
    end do
    write(*, ("(10x, a20)")) "ARRAY EXAMPLE"
    Write(*, nml=astro_nml)

    Open(unit=astro_file, file="z-astro_file.dat", status = "REPLACE")
    Write(unit=astro_file, nml=astro_nml)

    ASTRO_DATA= 1.0000000 , 2.0000000 , 3.0000000 , 4.0000000 , 5.0000000 ,
    1.1200000 , 2.1199999 , 3.1199999 , 4.1199999 , 5.1199999 ,
    A= 1.5000000 ,
    B= -3.5000000 ,
    C="just c ",
  6. Apr 30, 2012 #5
    As far as I know, there is no manual for Gfortran f90 under MinGW. I find myself writing in fortran several decades after I did it long ago out of necessity. I've picked up a few pdf files on it via Google, but they are somewhat incomplete, about a 100 pages or fewer. A few books I've found on Amazon about it cost $100+. No thanks on that. Fortunately, my task is confined to taking apart a few data files created with formats, and convert them into namelists. Lucky me. :-)
  7. Apr 30, 2012 #6
    Do you really NEED to convert them to namelists? I have never use namelists, I am doing fine.

    By the way, there are quite a few on-line resources for Fortran; no need to buy a book.
  8. May 2, 2012 #7
    Absolutely need them for my application. They are read as input to a computation program.
  9. May 2, 2012 #8
    So, you do no have the source to such "computation program" and that program has already been compiled, then.

    Otherwise, if you have the source to the program, nothing prevents you from simply reading values the typical way.

    Anyway, I guess is a matter of preference; it's just that namelists never seem to come up to the point that I thought nobody used them.

    Just like the local variables of third party library subroutines or functions, you do not need to know the name of the variables in them, you just need to pass values...this allows the programmer to change variable names to something more meaningful if so desired.

    ...with namelists, you need to keep variable names in program source and input files in sync.

    my 2 cents

    should you decide to do away from namelists, I am sure we can show you very efficient ways to read data.
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