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[christyleomin]

I am trying (or need to!) something I have never done in FORTRAN! I'm mainly into coding numerical stuff in Fortran.

Now, I need to write a binary file which is to be generated from another huge file (which contains enormous data).

Can anyone guide me in write direction? I know the info provided is a bit vague.Howver, if you can help or need more clarifications please let me know.

Thanks a lot in advance.

Christy

[christyleomin]

Please can anyone help urgently?

[PaulLaidler]

You may need to use unformatted WRITE statements using standard Fortran. Alternatively FTN95 has its own binary write via WRITEF@ etc.

[christyleomin]

Please can you suggest a reference/example concerning this (writing unformatted write statements)??

Please help

[JohnCampbell]

I'd recommend that you take the simpler approach and write using formatted write statements to a text file. There are a number of reasons I would recommend this.

1) It is easier to do text. Binary is for when you have sorted it all out and want to retain maximum real precision.
2) It is easier to check as you go. Open the text file with NOTEPAD and you can easily check what you have created.
3) If you are writing real numbers be sure that you retain sufficient precision in the format you use. This can also apply to large integers. You can fix this as you go.
4) Don't expect the first attempt will be the last version, so start with an easy part first, then build on it.

An example of writing information to (say) unit 12

OPEN (unit=12, file='Echo_output.txt', iostat=iostat) ! open the file
if (iostat /= 0) write (*,*) 'error opening file',iostat

do i = 1, many_numbers
write (12,2001) i, (iarray(j,i),j=1,a_few) ! assume integer
write (12,2002) i, (array(j,i),j=1,a_few) ! assume real
end do
2001 format ('Row',i6,' Iarray Values are', 20i8)
2002 format ('Row',i6,' Rarray Values are', 20es13.8 )

Finish with a CLOSE ane exit the program before you look at the results, as the file buffers must be cleared.

Do not write too many values to a single line.
Start with a simple approach and build on it.

You have not stated why you need the output and how you are going to use it. Importing into excel is a common requirement, so have a simple structure to your file. (think of what file layout you want !)

The next stage would be to include key words in the output and then be able to search for these words.

Hope this helps.

John

[christyleomin]

Thanks a lot.

Yes, I know to create a text file.

The idea of binary was as i need to export this file in a software (not Excel) which understands the binary format and carries out a finite element analysis (if you're not familiar with finite element analysis, it is a kind of engineering analysis).

I understand when creating in a binary format will be musch useful as the size will be much smaller than a regular text file in notepad as you (i.e.John) suggests.

Any ideas/examples of creating binary file?

Christy

[JohnCampbell]

Binary file formats vary across compilers.

To create a binary file you need to
! open
OPEN (unit=12, file='file_name', iostat=iostat, access='SEQUENTIAL', form='UNFORMATTED', status='UNKNOWN')

! then write
WRITE (12) ((array(i,j),i=1,n),j=1,m)

The write statement creates the "record" on the file, which consists of:
<header> <binary values> <trailer>

The problem is that the format of the <header> and <trailer> vary between compilers. FTN95 and IFORT are different. (FTN95 header format also varies, depending on the length of the record, so be careful. You need to read FTN95 help)

You can overcome this problem, by opening with access='TRANSPARENT' and then writing the <header> and <trailer> in a format expected by the FE program. You can also do this with access='DIRECT'.

Assuming that you are not transfering the files between operating systems, you do not need to consider the binary format. ( see Big-endian and little-endian if you need to go there )

An alternative could be to get FTN95 to provide a compiler option of compatible binary file formats, but this would need to consider which compiler file format to provide.

Years ago a goal of the fortran standard was to improve compatibility between different compilers. There are a few areas, like this, where the standard has gone missing.

You need to read the FTN95 and the FE documentation !

John

[IanLambley]

John et all,
I wrote a bit of example code to convert FTN95 unformatted data to the 4byte header method used by others, and back again.
Here they are:

[IanLambley]

And in the other direction:

[JohnCampbell]

Ian,

Since you have investigated the record structure of the FTN95 sequential binary format, I'd be interested in confirming the format.
What is the <header> format for FTN95 ? Is it a 2 byte / 6 byte mixed length count.
What is the count; bytes or 4-byte words ?
Does FTN95 have a <trailer> to allow backspace ?

I think the idea of a compiler option to standardise on a 4-byte header would be a good option.
I think there still remains the problem of if the length is bytes or words, as I think Lahey and Intel do vary with this. I think Intel provide a compiler switch for changing between bytes and words. The standard refers to "processor-dependent" or "file storage" units, so it's no help in standardising the operation across compilers!

I do successfully transfer binary files between Lahey and FTN95, but use a fixed length direct access file, which does not include the record length header in the file record.

John

[IanLambley]

John,
FTN95 header format seems to be

a. For records less than 255 bytes, a one byte length followed by the data terminated by the same one byte length. This allows reading forward and backspacing.

b. For records of length 255 and above, a one byte flag = ffh or -1 as a signed one byte integer, followed by a 4-byte length, the data and then followed by the 4-byte length and a one byte flag = ffh or -1.

So yes records have a trailer to allow backspace.

FTN95 use bytes as the storage size. I seem to remember that VAX F77 used words for record lengths in direct access files. Don't remember whether that was 2-byte or 4-byte - the latter I think. I would have to boot my VaxStation to find out!

Ian

[christyleomin]

Thanks a lot John and Ian,

John as you suggested, I'm reading the docuemntation for the FE part.Please can you suggest any reading refernce for Fortran documentation? Shall be really obliged.

Christy

[JohnCampbell]

Why not look at ftn95.chm; especially OPEN and FORM='UNFORMATTED'

lahey.com also has a fortran 95 reference .pdf which is set out in well.
http://www.lahey.com/docs/LangRefEXP72_revG04.pdf
It is a good reference document for the Fortran 95 language.

Using ACCESS='TRANSPARENT' you should be able to write a binary file, plus write the header and trailer in a compatible format to what the FE program expects. For writing a real*8 array A and HEADER is integer*4, the following should work.

HEADER = N*M*8 ! *8 for 1_byte units
WRITE (12) HEADER, ((A(i,j),i=1,n,j=1,m), HEADER

Remember to confirm what "file storage units" are being expected by the FE program. FTN95 and Lahey use bytes, while Intel uses 1-byte or 4-byte units (default), depending on the compiler option.

[christyleomin]

John, thanks a lot.Just a very absic question (sorry for that); you said;

To create a binary file you need to
! open
OPEN (unit=12, file='file_name', iostat=iostat, access='SEQUENTIAL', form='UNFORMATTED', status='UNKNOWN')

! then write
WRITE (12) ((array(i,j),i=1,n),j=1,m)

The write statement creates the "record" on the file, which consists of:
<header> <binary values> <trailer>

I don't get what you mean when you said;
The write statement creates the "record" on the file, which consists of:
<header> <binary values> <trailer>

What you mean by: header, trailer and binary values?

[JohnCampbell]

When you open a file as
access='SEQUENTIAL', form='UNFORMATTED'

You must use a binary write with a binary (unformatted) file:
write (12) ((array(i,j),i=1,n),j=1,m)

This creates a "record" on the file, which can be read with a :
read (12) ((array(i,j),i=1,n),j=1,m)

The record consists of the binary memory dump of "array". The fortran I/O routines also put a header and a trailer on the record to let the read (and backspace) statement know how long the record is so that the read statements can step from record to record. You don't have to read the full record, although this would be unusual. It is recommended that you use an identical READ to the WRITE

This is the structure of the record in the file.

You should read the the Elements of Fortran > Input/Output section of the Lahey fortran language documentation.
Binary files are easy to use. They are just difficult to look at.

John