Array reading error when opening multiple files in Fortran

In summary, you are trying to calculate the value of an array using data from two other arrays. The first array is open for reading, but the last array is not. The first IF block tests to see if the last array is open, and if not, the second IF block reads data from the first array. If the last array is open, data is also read from the second array.
  • #1
heliosplane
5
0
Guys. I really need help. I have been working in this little problem for hours. I had a problem in array reading when I opened more than 1 files, it seems like an array with different names mixed each other. Here is my code

Code: 
integer, parameter::size=11
real, dimension(101)    ::   cldata, alphadata
real, dimension(size)    ::   circ
integer:: i, j, nvals=0, nvals2=0, nvals3=0, status
Open (Unit=1, File='circdata.txt', status='old', Action='Read')
fileopen1: IF (status==0) then
    Write (*,1000) status
    1000 format (1x,'file alphadata open success--status = ',I6)
    do
        read(1,*,iostat=status) temp    !Get value
        if (status/=0) exit             !Exit on end of data
        nvals=nvals+1                   !Bump count
        circ(nvals)=temp                !Save value in array
    end do
else fileopen1
Write (*,1050) status
1050 format (1x,'file open failed--status = ',I6)
end if fileopen1

Open (Unit=2, File='alphadata.txt', status='old', Action='Read', Iostat=status)
fileopen2: IF (status==0) then
    Write (*,2000) status
    2000 format (1x,'file alphadata open success--status = ',I6)
    do
        read(2,*,iostat=status) temp    !Get value
        if (status/=0) exit             !Exit on end of data
        nvals2=nvals2+1               !Bump count
        alphadata(nvals2)=temp     !Save value in array
    end do
else fileopen2
Write (*,1060) status
1060 format (1x,'file open failed--status = ',I6)
end if fileopen2

Open (Unit=3, File='cldata.txt', status='old', Action='Read', Iostat=status)
fileopen3: IF (status==0) then
    Write (*,3000) status
    3000 format (1x,'file cldata open success--status = ',I6)
    do
        read(3,*,iostat=status) temp    !Get value
        if (status/=0) exit             !Exit on end of data
        nvals3=nvals3+1                 !Bump count
        cldata(nvals3)=temp             !Save value in array
    end do
else fileopen3
Write (*,1070) status
1070 format (1x,'file open failed--status = ',I6)
end if fileopen3

I have 2 arrays, A and B that I want to calculate, the A just need the file in open unit 1, and the last one need data from the file in open unit 2 and 3. When I deleted the open unit 2 and 3, my program worked just fine. But I needed those files for calculating array B. I had tried to put this last 2 opening syntax (unit 2 and 3) after the line to calculate the array A, but the program didn't work like it's supposed to be, element in array A became messy. I am really confused why this could happen, because I thought file in unit 2 and 3 don't relate with array A. Is there anything wrong with my syntax? or is it because my compiler, I am using the latest gfortran? Is there any other way that I can use?

Thanks in advance guys.
 
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  • #2
One thing which stands out. You have several named IF blocks like this:

fileopen1: IF blah blah

Else fileopen1
blah blah

End if fileopen1

I think you only need the fileopen1: label on the initial IF and End if fileopen1, but the Else statements in between do not need to refer to the initial label on the IF statement. The else statements are understood to be contained within the IF block and the label is not needed.
 
  • #3
just quick visual inspection (not compiling or trying to actually fix things)...

is this the entire program?...I don't see the "end program" statement.

the very first "Open" statement does not have the argument "iostat", so, I am not sure what the value of "status" is on the next line...

by the way, it is best to declare all your variables.

you seem to be re-using the variable "status" for various things...like message from opening file and message from reading data from the file...I would separate those things.

Also, I don't remember what the default line length is...some of you lines are longer than 72...are you passing a switch at compile time to allow for longer lines?
 
  • #4
SteamKing said:
One thing which stands out. You have several named IF blocks like this:

fileopen1: IF blah blah

Else fileopen1
blah blah

End if fileopen1

I think you only need the fileopen1: label on the initial IF and End if fileopen1, but the Else statements in between do not need to refer to the initial label on the IF statement. The else statements are understood to be contained within the IF block and the label is not needed.

Hi steamking. Thanks for your response. Yeah, it's correct, I have tried it and it still work. I just follow this style of writing from a book. I am really new in fortran and still lacking in doing improvement.
 
  • #5
gsal said:
just quick visual inspection (not compiling or trying to actually fix things)...

is this the entire program?...I don't see the "end program" statement.

the very first "Open" statement does not have the argument "iostat", so, I am not sure what the value of "status" is on the next line...

by the way, it is best to declare all your variables.

you seem to be re-using the variable "status" for various things...like message from opening file and message from reading data from the file...I would separate those things.

Also, I don't remember what the default line length is...some of you lines are longer than 72...are you passing a switch at compile time to allow for longer lines?

Hi gsal. Thanks for your response. It's just a part of codes, and I forget to post argument iostat in copying. About the default line, I have read about that issue in Chapman book, fortran 95/2003 for scientist and engineer, the default line length is 132 characters long.

Anyway after several trying, I have known the problem happening because I coincidentally change the option build target to debug option. After I change it back to release, It work normal again. Why debug option could cause this problem? I just googled and find out that debug option work just like debugger.

But I found a new problem regarding to this array. It's no more about opening file (I guess), but the problem happened if I wrote down an array to monitor that it will lead to mess up another array in previous operation. But the odd thing was my previous array works normal if I didnt write the new one to monitor although I still calculated it. Here is I include my full coding.

Code: 
Program Non_Linear_Lifting_Line

implicit none       !Force explicit declaration of variables

!Data dictionary: variable types, definitions, units
integer:: i, j, nvals=0, nvals2=0, nvals3=0, status !just index
integer, parameter::size=11    !setting size of array
real::deltay=1.1, PI=3.14285, k, V=30  !several variables
real::temp, temp2, final, initial !several variables
real, dimension(101)    ::   cldata, alphadata !AOA and Cl of Airfoil
real, dimension(size)   ::   alphai        !Induced angle of attack
real, dimension(size)   ::   alphaeff      !Effective angle of attack
real, dimension(size)   ::   circ !Circulation
real, dimension(size)   ::   alpha !Angle of attack
real, dimension(size)   ::   cl  !Cl for each spanwise
integer,dimension(size) ::   y  !Length of each spanwise

!Data dictionary: array data of y
y=(/(i,i=-5,5)/)

!Open and read data dictionary: array data of circulation
Open (Unit=1, File='circdata.txt', status='old', &
Action='Read', iostat=status)
fileopen1: IF (status==0) then
    Write (*,1000) status
    1000 format (1x,'file circdata open success--status = ',I6)
    do
        read(1,*,iostat=status) temp    !Get value
        if (status/=0) exit             !Exit on end of data
        nvals=nvals+1                   !Bump count
        circ(nvals)=temp                !Save value in array
    end do
else
Write (*,1050) status
1050 format (1x,'file open failed--status = ',I6)
end if fileopen1

!Input data for angle of attack condition
write(*,*) 'Input angle of attack (in deg): '
read(*,*) alpha(1)
do i=1,11
    alpha(i)=alpha(1)
end do

!Input data for velocity of flight condition
Write (*,*) 'Input velocity of flight (in m/s): '
read(*,*) V

!outest: do
!SIMPSON'S RULE TO FIND INDUCED ALPHA
!Just a constant
do i=1,11
    Write(*,*) 'circ = ', circ(i)
    Write(*,*) 'y = ', y(i)
end do

k=deltay/(12*PI*V)
!For spanwise station 1 to 6
do i=1, 6
    temp=alphai(i)
    temp2=y(i)
    if (temp2==y(1)) then
        temp2=temp2*0.01
    elseif (temp2==y(11)) then
        temp2=temp2*0.01
    end if
    initial=(((circ(2)-circ(1))/deltay)/(temp2-y(1)))
    final=(((circ(11)-circ(10))/deltay)/(temp2-y(11)))
    do j=1, 5
        if (temp2==y(2*j)) then
            temp2=temp2*0.69
        elseif (temp2==y(6)) then
            temp2=temp2+0.05
        end if
        temp=temp+4*(((circ(2*j+1)-circ(2*j))/deltay)/(temp2-y(2*j)))
    end do
    do j=1,4
        if (temp2==y(2*j+1)) then
           temp2=temp2*0.1
        elseif (temp2==y(6)) then
           temp2=temp2+0.1
        end if
        temp=temp+2*(((circ(2*j+2)-circ(2*j+1))/deltay)/(temp2-y(2*j+1)))
    end do
    alphai(i)=k*(temp+initial+final)
end do
!For spanwise station 7 to 11
do i=7, 11
    temp=alphai(i)
    temp2=y(i)
    if (temp2==y(1)) then
        temp2=temp2*0.01
    elseif (temp2==y(11)) then
        temp2=temp2*0.01
    end if
    initial=(((circ(2)-circ(1))/deltay)/(temp2-y(1)))
    final=(((circ(11)-circ(10))/deltay)/(temp2-y(11)))
    do j=1, 5
        if (temp2==y(12-2*j)) then
            temp2=temp2*0.69
        elseif (temp2==y(6)) then
            temp2=temp2+0.1
        end if
        temp=temp+4*(((circ(2*j+1)-circ(2*j))/deltay*(-1))/(temp2-y(12-2*j)))
    end do
    do j=1,4
        if (temp2==y(11-2*j)) then
           temp2=temp2*0.1
        elseif (temp2==y(6)) then
           temp2=temp2+0.1
        end if
        temp=temp+2*(((circ(2*j+2)-circ(2*j+1))/deltay*(-1))/(temp2-y(11-2*j)))
    end do
    alphai(i)=k*(temp+initial+final)
end do
!Write out alphai
do i=1,11
    Write(*,*) 'alphai = ', alphai(i)
end do

!Finding alphaeff
effective: do i=1,11
    alphaeff(i)=alpha(i)-alphai(i)
    alphaeff(i)=int(alphaeff(i)*10)/10    !Rounding to 1 decimal
end do effective
do i=1,11
    Write(*,*) 'alphaeff = ', alphaeff(i)
end do

!Open and Read data dictionary: array data of alphadata
Open (Unit=2, File='alphadata.txt', status='old', &
Action='Read', Iostat=status)
fileopen2: IF (status==0) then
    Write (*,2000) status
    2000 format (1x,'file alphadata open success--status = ',I6)
    do
        read(2,*,iostat=status) temp    !Get value
        if (status/=0) exit             !Exit on end of data
        nvals2=nvals2+1                 !Bump count
        alphadata(nvals2)=temp          !Save value in array
    end do
else
Write (*,1060) status
1060 format (1x,'file open failed--status = ',I6)
end if fileopen2

!Open and Read data dictionary: array data of cldata
Open (Unit=3, File='cldata.txt', status='old', &
Action='Read', Iostat=status)
fileopen3: IF (status==0) then
    Write (*,3000) status
    3000 format (1x,'file cldata open success--status = ',I6)
    do
        read(3,*,iostat=status) temp    !Get value
        if (status/=0) exit             !Exit on end of data
        nvals3=nvals3+1                 !Bump count
        cldata(nvals3)=temp             !Save value in array
    end do
else
Write (*,1070) status
1070 format (1x,'file open failed--status = ',I6)
end if fileopen3

!Matching alphaeff with (Cl)n from JavaFoil
Matching: do i=1,11
    temp=alphaeff(i)
    do j=1,101
        if(alphadata(j)==temp) then
            cl(i)=cldata(j)
        end if
    end do
end do Matching

Write (*,*) 'It"s still okay so far'

!Problem doesn't happen if I deleted this code block
do i=1,11
    Write (*,*) 'cl = ', cl(i)
end do

end program Non_Linear_Lifting_Line

If I write down the array cl(i) to monitor, 3 first element of array alphai(i) and alphaeff(i) became messy, but didn't happen if I didn't write it down. I am really really confused why writing down an array could change another array element. Really appreciate your help. I have been googling and don't know what to do or even what happen.
 
  • #6
baby steps...baby steps...

in addition to the editor window with your source code, open another one
take most of the calculation code out of your program and put it into the extra window
leave code that writes variable values to standard output ( "(*,*)" )
start putting code back a few lines at a time (compile and re-run) until the problem re-appears
get a hint of what might be happening


...by the way, I don't think your "rounding to 1 decimal" division is working as you desire...being that " int(*) " is an integer and 10 (as opposed to 10.0) is also an integer, " int(*)/10 " is going to be evaluated as integral division yielding an integer number with zero decimal places, regardless of the variable type on the left side of the equal sign.
 

1. What is an array reading error in Fortran?

An array reading error in Fortran refers to a situation where an array is not able to be properly read or accessed when opening multiple files. This can occur due to various reasons such as incorrect syntax, mismatched data types, or insufficient memory allocation.

2. How can I fix an array reading error in Fortran?

To fix an array reading error in Fortran, you can start by checking for any syntax errors in your code. Make sure that the array dimensions and data types are correctly defined. You can also try to allocate more memory for the array if it is too large. Additionally, you can use debugging tools to identify the specific cause of the error.

3. Why am I getting an array reading error when opening multiple files?

There are several reasons why you may be getting an array reading error when opening multiple files in Fortran. Some common causes include using incorrect file paths, trying to read data from a corrupted file, or attempting to read data in an incorrect format. It is important to carefully check your code and file inputs to identify the specific cause of the error.

4. Can I prevent an array reading error in Fortran?

Yes, you can prevent an array reading error in Fortran by carefully checking your code for any syntax errors and ensuring that the array dimensions and data types are correctly defined. It is also important to thoroughly test your code and handle any possible errors or exceptions that may arise when opening multiple files.

5. Are there any resources available for troubleshooting array reading errors in Fortran?

Yes, there are various resources available for troubleshooting array reading errors in Fortran. You can refer to the Fortran language documentation, online forums and communities, or consult with experienced Fortran programmers to get assistance with specific issues. Additionally, there are debugging tools and techniques that can help you identify and fix array reading errors in your code.

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