Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Loading 2D array files to Fortran variables

  1. Apr 14, 2009 #1

    I have created data files by compiling and running a c++ code. Now I
    need to open and store the contents of these files in Fortran 77
    variables. But I am not able to do this. The read command does not
    return the values stored in the file.
    The files are having some 2003 lines and 53 colomns. The values are in
    the form "2.885531e+002" (positive) and "-7.687902e+001" (negative)
    with 1 space seperating different values.

    Thank you in advance!
  2. jcsd
  3. Apr 14, 2009 #2


    User Avatar

    Staff: Mentor

    Can you show us the code that you tried to use for reading the file?
  4. Apr 14, 2009 #3
    The entire code is very long, so I will only write the part where the file is opened and read. I have tried many different formats, here is the last format I tried with:

    REAL EVg(2003,53)
    read(1,10,iostat=k) EVg
    10 format(53(G7E3,1X))

    the iostat has returned different values (-1, 0, 115, etc.) for different format cases I have tried. For the case above it returns 0, but the "EVg" array does not contain the array values.
  5. Apr 14, 2009 #4


    User Avatar

    Staff: Mentor

    It's been a long time since I had to deal with this sort of thing, but as I recall, the basic principles are these: (1) When the number of values to be input exceeds the number of specifiers in the format statement, the format simply repeats itself. (2) All data in a single input statement is assumed to be on one line, unless the format specifies otherwise.

    So I think your program is trying to read the entire array from the first line of the input file. Try adding a slash at the end of the format, which should skip to the next line:

    10 format(53(G7E3,1X)/)

    This may still give you problems if the file doesn't have a blank space after the last number on each line.

    Also, I don't remember a format specifier like "G7E3", but my Fortran experience ended with Fortran 77.
    Last edited: Apr 14, 2009
  6. Apr 14, 2009 #5
    I don't either.
    In fact, the enhanced format specifiers (E,F,G) are mostly for displaying pretty output.
    For input, an E,F, or G specifier will accept both 123456.78 or 1.1234E6, as shown in the following example code. The input I gave was 1.123456E+012 1.123456e+013 .
    The output was printed correctly.
    Code (Text):

    C test fortran format
          REAL*8 A,B
    C   1 FORMAT(2(F13.6,1X))
    C   1 FORMAT(2(E13.6,1X))
        1 FORMAT(2(G13.6,1X))
          PRINT *,A,B
    Do not forget the extra space at the end of the line, it is required.
    If you still have problems, post a few lines of your input, using the code option so we see exactly how the data are laid out.
    Also, check if the spaces between the data are aligned. The format above expects them to be aligned. If you have a problem with data alignment, write a c-program to read in and write them out aligned. That would be easier to do to figure out how to read it using free-format input.
  7. Apr 15, 2009 #6
    Thank you for your response!
    I should maybe add that I am working in Fortran 77 enviroment (due to limitations).
    The data in the files basically look like:
    Code (Text):
    +0.000000e+000 -7.281896e+002 -1.791944e+003
    +0.000000e+000 -7.856508e+002 -1.824643e+003
    -1.325604e+005 -8.411246e+002 -1.856220e+003
    this is taken from somewhere in the middle of the file, at another place it looks like:
    Code (Text):
    -1.045771e+005 +1.047517e+004 -1.180211e+003
    -5.662817e+004 +1.152035e+005 -1.173054e+003
    +1.187847e+004 +2.266384e+005 -1.165909e+003
    as you can see the data are (now) aligned, (as I added '+' in front of positive values) and the extra space at each line end is there. There is also an line termination after the extra space of the last line.
    The file reading procedure:
    Code (Text):
    REAL EVg(2003,53)
    read(1,10,iostat=k) EVg
    10 format(53(E13.6,1X)/)
    returns k=0 and EVg a matrix of zeros.
  8. Apr 16, 2009 #7
    Indeed, an error in the format will cause the numbers read in to become zeroes.

    Using the following code:
    Code (Text):

    C testREAD fortran format
          REAL*8 EVg(6,3)
          DO 5 I=1,6
        5 READ(1,FMT='(3E15.6)',END=15)(EVg(I,J),J=1,3)
       15 close(1)
          DO 20 I=1,6
       20 WRITE(6,FMT='(SP,3(1PE15.6E3))')(EVg(I,J),J=1,3)
    and reading the six lines you supplied from a data file, I obtain the following output:
    Code (Text):

    +0.000000E+000 -7.281896E+002 -1.791944E+003
    +0.000000E+000 -7.856508E+002 -1.824643E+003
    -1.325604E+005 -8.411246E+002 -1.856220E+003
    -1.045771E+005 +1.047517E+004 -1.180211E+003
    -5.662817E+004 +1.152035E+005 -1.173054E+003
    +1.187847E+004 +2.266384E+005 -1.165909E+003
    Hope that helps to solve your problem.
  9. Apr 17, 2009 #8
    I have now tried with the following (on a somewhat smaller file [2001][12]),
    Code (Text):
    DO t=1,2001
    DO t=1,2001
    The iostat returns -1, if I change the format to
    Code (Text):
    as it should be iostat returns 100.
    For both formats I still get a EVg to be an array of 0's.

    Can there be a problem with the compiler I am using? I am using the "mingw32-make.exe" which runs a "g77 -c -O2 fortran.f" and a "g77 -s -o file.exe dimdef.o newmods.o comtac.o fgnmod.o usernl.o analyt.o devt69.o usrfun.o hopcod.o user10.o tpbig.a dislin.a -luser32 -lgdi32 -lcomdlg32".
  10. Apr 17, 2009 #9
    I cannot pronounce anything until you show the actual data you are using with 12 numbers on the same line. In Fortran, the size of each field is important. Even an extra space at the end of the line could be significant. The number of lines is not important in this case.

    If you could post 4-5 lines of data, then I'll see how the data fits in with the format.
    If we don't find anything there, then we may have to worry about the compiler.
    Last edited: Apr 17, 2009
  11. Apr 18, 2009 #10
    Here are 5 lines taken from the middle of the data file:
    Code (Text):
    +1.670000e-006 +0.000000e+000 -8.540156e+006 -1.585399e+003 -2.243492e+003 -2.763622e+003 -3.142946e+003 -3.299538e+003 -3.304998e+003 -3.342794e+003 -3.706140e+003 -4.368216e+003
    +1.680000e-006 -9.375357e+004 -8.037304e+006 -1.612638e+003 -2.255844e+003 -2.763778e+003 -3.130649e+003 -3.279551e+003 -3.282095e+003 -3.319731e+003 -3.677900e+003 -4.360687e+003
    +1.690000e-006 -2.859594e+005 -7.588826e+006 -1.639665e+003 -2.269052e+003 -2.765124e+003 -3.119963e+003 -3.261429e+003 -3.261483e+003 -3.300265e+003 -3.655372e+003 -4.347075e+003
    +1.700000e-006 -6.289417e+005 -7.239074e+006 -1.666989e+003 -2.283188e+003 -2.767609e+003 -3.110709e+003 -3.244538e+003 -3.242276e+003 -3.283470e+003 -3.638555e+003 -4.326224e+003
    +1.710000e-006 -1.137889e+006 -7.009578e+006 -1.694831e+003 -2.298037e+003 -2.770898e+003 -3.102424e+003 -3.228056e+003 -3.223421e+003 -3.268063e+003 -3.626592e+003 -4.298185e+003
    It is a space after the last values of every line (the option apperently removes extra space after the last value).
  12. Apr 19, 2009 #11
    Sorry it took a little more time than I thought would take, but I have remodelled the program to make it a little more general in order to read in a variable number of lines and fields. It seems to read in and write correctly.
    You could try with this new version and make adaptations required for your purposes:
    Code (Text):

    C testREAD fortran format
          REAL*8 EVg(5,12)
          WRITE(WRITEFMT,'(4H(SP,,I2,12H(1PE15.6E3)) )')NFIELDS
    C     (12E15.6)           (SP,12(1PE15.6E3))
          IF(IOS.NE.0) THEN
            PRINT *,'ERROR IOS=',IOS
          DO 5 I=1,NLINES
        5 CONTINUE
       15 close(1)
          DO 20 I=1,NLINES
       20 CONTINUE
    C     FORMAT(SP,12(1PE15.6E3))
    Code (Text):

    +1.670000E-006 +0.000000E+000 -8.540156E+006 -1.585399E+003 -2.243492E+003 -2.763622E+003 -3.142946E+003 -3.299538E+003 -3.304998E+003 -3.342794E+003 -3.706140E+003 -4.368216E+003
    +1.680000E-006 -9.375357E+004 -8.037304E+006 -1.612638E+003 -2.255844E+003 -2.763778E+003 -3.130649E+003 -3.279551E+003 -3.282095E+003 -3.319731E+003 -3.677900E+003 -4.360687E+003
    +1.690000E-006 -2.859594E+005 -7.588826E+006 -1.639665E+003 -2.269052E+003 -2.765124E+003 -3.119963E+003 -3.261429E+003 -3.261483E+003 -3.300265E+003 -3.655372E+003 -4.347075E+003
    +1.700000E-006 -6.289417E+005 -7.239074E+006 -1.666989E+003 -2.283188E+003 -2.767609E+003 -3.110709E+003 -3.244538E+003 -3.242276E+003 -3.283470E+003 -3.638555E+003 -4.326224E+003
    +1.710000E-006 -1.137889E+006 -7.009578E+006 -1.694831E+003 -2.298037E+003 -2.770898E+003 -3.102424E+003 -3.228056E+003 -3.223421E+003 -3.268063E+003 -3.626592E+003 -4.298185E+003
  13. Apr 23, 2009 #12
    Thank you, it is working now. I was stuck with these lines for more than 2 weeks.... but now everything is working.
  14. Apr 23, 2009 #13
    Glad that everything works out, come and visit us often!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Loading 2D array files to Fortran variables
  1. FORTRAN 90 2d arrays (Replies: 6)