4. Salford Fortran 90 Compiler

4.1. Introduction

In principle this compiler, FTN90, has now been superseded by the Salford Fortran 95 Compiler, FTN95. However, whilst FTN90 happily links to all the NAg numerical libraries that we have installed on the Novell Network here at UMIST --- Fortran 77 and Fortran 90 --- FTN95 does not: it will link to the (Mark 19) F77 libraries, but not to the (Release 3) F90 libraries. (Correspondence with NAg suggests that in the near future this situation will not be "corrected".)

The Salford FTN90 compiler can be used to compile both Fortran 90 and Fortran 77 source files.

4.2. Menu Entries

     Start->Programs->Compilers->Salford FORTRAN

4.3. Ensuring Your Path is Set Correctly

In general, if you wish to use FTN90 at the command-line or through a batch-file, you will need to ensure your PATH environment variable is set correctly --- this is done for you if you use the Start Menu to start command-line FTN90 (see above). The FTN90 compiler, and its supporting libraries, are located at:

M:\PROGRAMF\SALFORD_FTN90_<version>

where <version> is 2.191 at the time of writing (and hence the full path is M:\PROGRAMF\SALFORD_FTN90_v2_191.) The simplest way to use the FTN90 compiler is to ensure that the above location is on your path. This will ensure that executable files (including FTN90 and SLINK) and necessary libraries are found, and can be done by running a batch file called ftn90var.bat. To do this, at a command-line ("DOS box") type:

M:\PROGRAM FILES\SALFORD_FTN90_<version>\FTN90VAR

(no ".bat") and "hit return". Alternatively, you can check and set your path manually. Again, at a command-line:

1. Type PATH and "hit return"; you should see something similar to this...

   PATH=C:\WINNT\system32;C:\WINNT;W:.;Z.;

   ...possibly a rather longer line (or lines) of text.
2. If this does not include M:\PROGRAM FILES\SALFORD_FTN90_<version> (it probably won't) then type exactly:

   PATH=M:\PROGRAM FILES\SALFORD_FTN90_<version>;%PATH%

   and hit return; this will add the Salford compiler directory to your path --- you should now be able to use the FTN90 compiler at the command line.

4.4. Basic Usage

To compile a file, such as my_file.f90, the formal command is

FTN90 <source-file>

for example

FTN90 my_file.f90

or

FTN90 my_file

(either is fine). If there are no errors in the source file, my_file.f90, then an object file will be generated called my_file.obj. This needs to be linked to produce an executable file:

SLINK $ LOAD my_file $ FILE

This will produce a file called my_file.exe which can be run in the usual way. These two steps can be combined by issuing the /LINK option to the compiler:

FTN90 my_file /LINK

The latter works for an executable built from a single source file only.

4.5. An Example

For example, using your favourite text editor, save the following simple programme into a file called C:\work\hello.f90

! -- A simple Fortran 90 programme: a greeting is printed at the ! command line. PROGRAM hello PRINT *, "Hello world!" END PROGRAM hello

To compile and link the programme, within the directory/folder C:\work, type the command FTN90 hello.f90 /LINK, hit return and observe the output:

C:\work>FTN90 hello.f90 /LINK [FTN90/WIN32 Version 2.191... ... NO ERRORS [FTN90] Creating executable: hello.EXE

then, once the compilation/linking has finished run the programme by typing hello:

C:\work>hello Hello world!

4.6. Programmes with Multiple Source Files

  MODULE strings

  IMPLICIT NONE
  CONTAINS

    SUBROUTINE print_string(string)
      IMPLICIT NONE
      CHARACTER(LEN=*), INTENT(IN) :: string
        PRINT *, string
    ENDSUBROUTINE print_string

  END MODULE strings

  PROGRAM hello
  USE strings
    CALL print_string("Hello world three!");
  END PROGRAM hello

    C:\work>FTN90 strings 
    ...
        NO ERRORS  [FTN90]
    C:\work>FTN90 hello
    ...
        NO ERRORS  [FTN90]

    SLINK
    $ LOAD strings
    $ LOAD hello
    $ FILE
    Creating executable: C:\work\hello.EXE

    C:\work>hello
     Hello world!

4.7. .mod files and the /MOD_PATH option

When a Fortran 90 MODULE is compiled most (all?) compilers produce an auxiliary file, usually with a suffix of .mod. This file contains (amongst other things) the number and type of arguments expected by each SUBROUTINE and FUNCTION exported by the module. Using this, the compiler can check that each call to a subroutine/function by a client of the module is correct.

If the .mod files corresponding to USEd MODULEs are not in the current directory, the compiler needs to be told where to look (e.g., when using the NAg libraries --- see below). This is achieved by using the /MOD_PATH compiler option --- see below.

4.8. Important Compiler Options

/MOD_PATH

Tells the compiler where to look for .mod files, for example

FTN90 /MOD_PATH M:\NAG\FNW3203D9\NAG_MOD_DIR NAG_FFT_EX01.F90

/FIXED and /FREE

These compiler options specify the source code format to be expected: /FIXED specifies Fortran 77-style fixed format; /FREE specifies Fortran 90-style free format. (The default for filenames with suffix .FOR is /FIXED; other wise free-format is expected.)

/CHECK_SUBS

By default the Salford FTN90 compiler does not check array bounds. This produces significantly faster code but means that programmes can behave in unpredictable, system-dependent ways (produce incorrect results or simply crash) owing to undetected bugs. The /CHECK_SUBS (check subscripts) option ensures array-bound-checking code is added to a programme.

4.9. Automating Builds

Compilation and linking of programmes built from multiple source-files though the command-line can become tedious. The simplest solution is to automate the procedure by means of a batch file. Here is an example:

ftn90 /mod_path C:\work strings.f90 if errorlevel 1 goto err2 ftn90 /mod_path C:\work hello.f90 if errorlevel 1 goto err2 echo load strings.obj > slink.lst echo load hello.obj >> slink.lst echo file hello >> slink.lst slink slink.lst :err1 echo strings: failed to compile :err2 echo hello: failed to compile

A more powerful option is to use Cygwin's make utility --- this is a port of the GNU make utility found on Unix systems.

4.10. On-disk Help

On-disk help is provided in the usual way for Windows applications. The help file may be found at

M:\PROGRAM FILES\SALFORD\FTN90.HLP