I am trying to compile someone else's FORTRAN code using gfortran 4.4.6. The original coder used something like Compaq FORTRAN.
The code in question is supposed to read a filename like 'foo.txt' and create a new file called 'foo_c.txt':
file_label_end = SCAN(filename, '.') - 1
WRITE (output_filename,5) filename
5 FORMAT (A<file_label_end>, '_c.txt' )
gfortran complains about the opening angle bracket of the character specifier. That is, rather than "A3" he has "A<(a variable with value 3)>". I cannot find any information about interpolating format widths from variables... Is this possible? If not, what's the best way to fix this?
Update:
This seems to be working (compiling):
file_label_end = SCAN(par_filename, '.', .TRUE. ) + 1
output_filename = par_filename(1:file_label_end) // '_c.par'
but I later have a similar case:
12 FORMAT (<n-1>F10.5)
...
READ(1,12) (cat_parm (blk,j), j = 1,n-1)
which I attempted to fix by creating a format string:
write(fmt12,'(I0,A4)') n-1, 'F10.5'
!12 FORMAT (fmt12)
12 FORMAT (fmt=fmt12)
But the "t" in "fmt" gets flagged with an error about "Nonnegative width required in format string"
The use of <> in Fortran edit descriptors is non-standard, though widely implemented. You certainly can build edit descriptors from variables, the standard way is through an internal write, something like this (omitting declarations):
format_string = ''
write(format_string,'(a1,i0,a6)') 'A', file_label_end,'''_c.txt''' ! WARNING I haven't tested this
and then
write(output_filename,fmt=format_string) filename
But in your case this is not entirely necessary. You could try this instead
file_label_end = SCAN(filename, '.') - 1
WRITE (output_filename,'(a)') filename(1:file_label_end)//'_c.txt'
With the 'a' edit descriptor omitting a width means that all the characters in the expression will be written. You may want to declare
character(len=*), allocatable :: output_filename
if you haven't already done so.
The easiest is to use modern fortran
WRITE (output_filename,'(a)') trim(filename) // '_c.txt'
Otherwise I would write the number in the format string using a similar internal write.
Related
I'm trying to read some data from a file, and the endfile record detection is important to stop reading. However, depending of the array dimensions of the array used to read data, I cannot detect properly the endfile record and my Fortran program stops.
The program is below:
!integer, dimension(3) :: x ! line 1.1
!integer, dimension(3,10) :: x ! line 1.2
integer, dimension(10,3) :: ! line 1.3
integer :: status,i=1
character(len=100) :: error
open( 30, file='data.dat', status='old' )
do
print *,i
!read( 30, *, iostat=status, iomsg=error ) x ! line 2.1
!read( 30, *, iostat=status, iomsg=error ) x(:,i) ! line 2.2
read( 30, *, iostat=status, iomsg=error ) x(i,:) ! line 2.3
if ( status < 0 ) then print *,'EOF'
print *,'total of ',i-1,' lines read.'
exit
else if ( status > 0 ) then
print *,'error cod: ',status
print *,'error message: ', error
stop
else if ( status == 0 ) then
print *,'reading ok.'
i = i + 1
end if
end do
With 'data.dat' file been:
10 20 30
30 40 50
When lines 1.3 and 2.3 are uncommented the mentioned error appears:
error cod: 5008
error message: Read past ENDFILE record
However, using lines 1.1 and 2.1, or 1.2 and 2.2, the program works, detecting endfile record.
So, I would like some help on understanding why I cannot use lines 1.3 and 2.3 to read properly this file, since I'm giving the correct number of array elements for read command.
I'm using gfortran compiler, version 6.3.0.
EDIT: simpler example
the following produces a 5008 "Read past ENDFILE record" error:
implicit none
integer x(2,2),s
open(20,file='noexist')
read(20,*,iostat=s)x
write(*,*)s
end
if we make x a scalar or a one-d array ( any size ) we get the expected -1 EOF flag. It doesn't matter if the file actually doesn't exist or is empty. If the file contains some, but not enough, data its hard to make sense of which return value you might get.
I am not sure if I am expressing myself correctly but it has to do with the way fortran is reading and storing 2d-arrays. When you are using this notation: x(:,i), the column i is virtually expanded in-line and the items are read using this one line of code. In the other case where x(i,:) is used, the row i is read as if you called read multiple times.
You may use implied loops if you want to stick with a specific shape and size. For example you could use something like that:read( 30, *, iostat=status, iomsg=error ) (x(i,j), j=1,3)
In any case you should check that your data are stored properly (as expected at least) in variable x.
Please note this is only a guess. Remember that Fortran stores arrays in column major order. When gfortran compiles read() x(:,i), the 3 memory locations are next to each other so in the executable, it produces a single call to the operating system to read in 3 values from the file.
Now when read() x(i,:) is compiled, the three data elements x(i,1), x(i,2) and x(i,3) are not in contiguous memory. So I am guessing the executable actually has 3 read calls to the operating system. The first one would trap the EOF but the 2nd one gives you the read past end of file error.
UPDATE: I have confirmed that this does not occur with Intel's ifort. gfortran seems to have had a similar problem before: Bad IOSTAT values when readings NAMELISTs past EOF. Whether this is a bug or not is debatable. The code certainly looks like it should trap an EOF.
I have an input file that I cannot alter the format. One of the lines in particular can contain either 6 or 7 reals and I don't have any way of knowing ahead of time.
After some reading, my understanding of the list-formatted read statement is that if I attempt to read 7 reals on a line containing 6, it will attempt to read from the next line. The author of the code says that when it was written, it would read the 6 reals and then default the 7th to 0. I am assuming he relied on some compiler specific behavior, because I cannot find a mention of this behavior anywhere.
I am using gfortran as my compiler, is there a way to specify this behavior? Or is there a good way to count a number of inputs on a line and rewind to then chose to read the correct number?
here is a little trick to accomplish that
character*100 line
real array(7)
read(unit,'(a)')line !read whole line as string'
line=trim(line)//' 0' !add a zero to the string
read(line,*)array !list read
If the input line only had 6 values, the zero is now the seventh.
If there were seven to begin with it will do nothing.
I try to avoid using format specifiers on input as much as possible.
Maybe you should use the IOSTAT statement for detecting the wrong format when you attempt to read 7 values when there are only 6. And you should use the ADVANCE statement to be able to retry to read the same line.
READ(LU,'7(F10.3)', IOSTAT=iError, ADVANCE='NO') MyArray(1:7)
IF(iError > 0) THEN
! Error when trying to read 7 values => try to read 6 !
READ(LU, '6(F10.3)') MyArray(1:6)
ELSEIF(iError == 0) THEN
READ(LU, *) ! For skipping the line read with success with 7 values
ENDIF
IOSTAT takes a negative value for example when you reach the end of the file, positive for problem of reading (typically formatting error) and 0 when the read succeed. See this link for a complete definition of gfortran error code: http://www.hep.manchester.ac.uk/u/samt/misc/gfortran_errors.html
Another way to do it could be to read the line as a string and manipulating the string in order to get the vector values :
CHARACTER(LEN=1000) :: sLine
...
READ(LU, '(A)') sLine
READ(sLine,'7(F10.3)', IOSTAT=iError) MyArray(1:7)
IF(iError > 0) THEN
! Error when trying to read 7 values => try to read 6 !
READ(sLine, '6(F10.3)') MyArray(1:6)
ENDIF
If the values are written in fixed format, you can determine the lenght of the vector by testing the lenght of the line:
CHARACTER(LEN=1000) :: sLine
INTEGER :: nbValues
CHARACTER(LEN=2) :: sNbValues
...
READ(LU, '(A)') sLine
nbValues = LEN_TRIM(sLine) / 10 ! If format is like '(F10.x)'
WRITE(sNbValues, '(I2)') nbValues
READ(sLine, '('//TRIM(sNbValues)//'(F10.3))') MyArray(1:nbValues)
On internet, I found this program that demonstrate Evaluating elliptic integrals of first and second kinds (complete)
implicit none
real*8 e,e1,e2,xk
integer i, n
e=1.d-7
print *,' K K(K) E(K) STEPS '
print *,'------------------------------------------'
xk=0.d0
do i = 1, 20
call CElliptic(e,xk,e1,e2,n)
write(*,50) xk,e1,e2,n
xk = xk + 0.05d0
end do
print *,'1.00 INFINITY 1.0000000 0'
stop
50 format(' ',f4.2,' ',f9.7,' ',f9.7,' ',i2)
end
Complete elliptic integral of the first and second kind. The input parameter is xk, which should be between 0 and 1. Technique uses Gauss' formula for the arithmogeometrical mean. e is a measure of the convergence accuracy. The returned values are e1, the elliptic integral of the first kind, and e2, the elliptic integral of the second kind.
Subroutine CElliptic(e,xk,e1,e2,n)
! Label: et
real*8 e,xk,e1,e2,pi
real*8 A(0:99), B(0:99)
integer j,m,n
pi = 4.d0*datan(1.d0)
A(0)=1.d0+xk ; B(0)=1.d0-xk
n=0
if (xk < 0.d0) return
if (xk > 1.d0) return
if (e <= 0.d0) return
et n = n + 1
! Generate improved values
A(n)=(A(n-1)+B(n-1))/2.d0
B(n)=dsqrt(A(n-1)*B(n-1))
if (dabs(A(n)-B(n)) > e) goto et
e1=pi/2.d0/A(n)
e2=2.d0
m=1
do j = 1, n
e2=e2-m*(A(j)*A(j)-B(j)*B(j))
m=m*2
end do
e2 = e2*e1/2.d0
return
end
I have compiled it but I have received the following errors:
gfortran -Wall -c "gauss.f" (nel direttorio: /home/pierluigi/Scrivania)
gauss.f:53.9:
50 format(' ',f4.2,' ',f9.7,' ',f9.7,' ',i2)
1
Error: Invalid character in name at (1)
gauss.f:83.72:
if (dabs(A(n)-B(n)) > e) goto et
1
Warning: Deleted feature: Assigned GOTO statement at (1)
gauss.f:83.35:
if (dabs(A(n)-B(n)) > e) goto et
1
Error: ASSIGNED GOTO statement at (1) requires an INTEGER variable
gauss.f:48.18:
write(*,50) xk,e1,e2,n
1
Error: FORMAT label 50 at (1) not defined
Compilation failed.
Any suggestions please?
EDIT
I have read all your answers and thanks to you I managed to compile the program. I also have another curiosity and I do not know whether to write another question. In the meantime I modify this question. In my program, xk is increased by 0.05. Now I will that the program to read data from a file containing: the minimum value of xk; the maximum value of xk; the number of intervals. I thought:
open (10,file='data/test')
read (10,*) xkmi, xkma
read (10,*) nk
close (10)
lkmi = dlog(xkmi)
lkma = dlog(xkma)
ldk = (lkma-lkmi)/dfloat(nk-1)
In addition, the program must be modified in such a way that the result is written to another file. How can I change the rest of the program? Thank you very much.
Your source code file extension is f which, I think (check the documentation), tells gfortran that the file contains fixed source form. Until Fortran 90 Fortran was still written as if onto punched cards and the location of various bits and pieces of a line is confined to certain columns. A statement label, such as 50 in the first of the error messages, had to be in columns 1 - 6. Two solutions:
Make sure the label is in (some of) those columns. Or, better
Move to free source form, perhaps by changing the file extension to f90, perhaps by using a compilation option (check your documentation).
The error raised by the goto et phrase is, as your compiler has told you, an example of a deleted feature, in which the goto jumps to a statement whose label is provided at run-time, ie the value of et. Either tell your compiler (check ...) to conform to an old standard, or modernise your source.
Fix those errors and, I suspect, the other error messages will disappear. They are probably raised as a consequence of the compiler not correctly parsing the source after the errors.
Because the file has type ".f" gfortan is interpreting it as fixed-source layout. Trying compiling with the free-form layout by using compiler option -ffree-form and see if that works. This probably explains the error about the "invalid character". That statement not being recognized explains the "format not defined error". The "computed goto" is obsolete but valid Fortran. You can ignore that warning. If you wish, later you can modernize the code. For the remaining error, for the "assigned goto", declare "et" as an integer.
I would just do this
10 n = n + 1
! Generate improved values
A(n)=(A(n-1)+B(n-1))/2.d0
B(n)=dsqrt(A(n-1)*B(n-1))
if (dabs(A(n)-B(n)) > e) goto 10
and possibly compile as free form source as others have shown. The label et seems weird and non-standard, possibly a rare vendor extension.
You could also change the lines above to a do-loop with an exit statement (Fortran 90).
(The program compiled for me after the change).
I tested the subroutine and compared with matlab and it was not the same. It is very similar to the algorithm used in Abramowitz's book. Here is the one I wrote that works well, just for comparing.
subroutine CElliptic(m,K,E)
implicit none
real*8 m,alpha,E,K,A,B,C,A_p,B_p,C_0,pi,suma
integer j,N
N=100
alpha=asin(sqrt(m))
pi = 4.d0*datan(1.d0)
A_p=1.0
B_p=cos(alpha)
C_0=sin(alpha)
suma=0.0
do j=1,N
A=(A_p+B_p)/2.0d0
B=dsqrt(A_p*B_p)
C=(A_p-B_p)/2.0d0
suma=suma+2**(j)*C**2
A_p=A
B_p=B
end do
K=pi/(2*A)
E=(1-1.d0/2.d0*(C_0**2+suma))*K
end Subroutine CElliptic
best regards
Ed.
I am editing a fortran 90 to read a file. A particular file happens to be 'contaminated' with some extra information, so I wanted to attempt a read and then rewind; reread if in error:
open(filenum,file=filename,form="unformatted",iostat=ierr) //'direct' access
...lots of stuff...
here = ftell(filenum)
read(filenum,iostat=ierr) var1, var2 //try reading as var1, var2
if(iswrong(var1, var2)) then //check if correct
call fseek(filenum,here-ftell(filenum),1) //rewind
read(filenum,iostat=ierr) vara, varb, varc //read as different type
endif
However, when I compile this program, I get
Undefined symbols:
"_fseek_", referenced from:
___myreader__subroutine_name in myreader.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
(I am trying to compile on gfortran (i686-apple-darwin8-gfortran-4.2)). I understand that fseek is not a standard fortran routine.
I wonder if there is an alternative. I understand I can do something like read(filenum,rec=somevalue) but how can I use this in a similar fashion? I also thought to attempt reading with read(,advance='no') for testing and then reading again with advance='yes' if it is in the correct format, but this requires a specific format expression, which is not specified. Thank you.
You have to use backspace to go back to the previous record. Traditional Fortran IO is record based, non stream based (like in C)
On Linux and Windows, it is okay in general to compute seek offsets.
However, on record-oriented file systems (OpenVMS, OS/370, NOS, etc.), the value which comes from ftell() is a magic cookie and cannot be inspected or processed using trivial arithmetic to compute a new file location. Instead, use the rewind statement to go back to the beginning of a file (if it is indeed seekable).
There is another technique for processing input if you are uncertain about the file contents -- in this case sometimes the files contents are incorrect or different -- which is to read into a string, then examine the contents of the string. If the contents are valid you can use a read statement to read from the string. Or if the contents are "different", use a different read statement, or take appropriate action. No rewind or backspace is necessary. You do have to guess the longest possible line length to declare the length of the string.
I'm currently porting an application from Fortran to C and need to output some variables to compare results. I'm very new to Fortran, and although i understand the code and have now ported several thousand lines, I'm a noob at writing Fortran code myself.
This code:
write(6,'(A,I3,A,E12.8,A,E12.8,A,E12.8,A,E12.8,A,E12.8)') 'iHyd:',
& ih,'; dzdr: ',dzdr,'; tauray:', tauRay,'; zRay: ',
& zray,'; ampRay: ',realpart(aray),'+j*',
& imagpart(aray),'; qRay: ',qray,'; width :',w
Compiles fine, but when run, the program exits with:
At line 296 of file calcpr.for (unit = 6, file = 'stdout')
Fortran runtime error: Expected INTEGER for item 15 in formatted transfer, got REAL
(A,I3,A,E12.8,A,E12.8,A,E12.8,A,E12.8,A,E12.8)
^
q0: 1432.3944878270595
nArrayR: 501 nArrayZ: 201
iHyd: 1; dzdr: ************; tauray:************; zRay: ************; ampRay: NaN+j* NaN
; qRay:
Besides being really ugly, it doesn't make much sense to me, as ìh is declared as integer*8 and not as real.
So how can i solve this?
I'm counting 6 character&variable specifications in the format statement, but you're printing 8 of them.
edit:
a nicer use of the format statement would be '(A,I3,7(A,E12.8))'
Fortran "recycles" the format if there are more things to be printed than specified in the format statement. If a write statement gives results you don't understand, to diagonose the problem it may be helpful to remove the things printed one at a time until the error goes away.
It says "item 15", which I would take to be down near the end of your list, not ih at the beginning. It's clear that both "w" and "qray" are being printed as REAL; is either one of them an INTEGER? You may need to change the format specifier then.