20 Sep 2026

Notes on the port and build instructions for 
ddfun-v04 under Silverfrost FTN95 Personal Edition

K. Myneni
krishna.myneni@ccreweb.org

The following source files have been modified from
their original gfortran files to make the ddfun 
library work under FTN95:

ddfuna.f90
second.f90

I also added some diagnostic statements in the
program testddfun.f90.

Diagnostic statements have been added for
troubleshooting problems with a few subroutines,
and these are now commented, except for those
in testddfun.f90. 

The value of KIND for real variables differs from 
gfortran and FTN95 and adjustments have been made
for this difference.

I don't know how to turn off optimizations in FTN95
and this affects the original gfortran code for 
splitting a double double number into two double 
precision numbers. Therefore, I recoded those 
subroutines in ddfuna.f90 which perform splitting 
(search for 'split' to find the modified) to obtain 
correct behavior for the splitting.

For some special functions, such as the various types
of Bessel functions, the FTN95-compiled and linked
testddfun.exe gives larger error in comparison with 
the resuts from the gfortran testddfun executable. 
See the text file, 

testddfun-results_20260919.txt

Conversions from decimal double double input to
two binary double precision numbers, and conversion 
from two decimal double precision inputs to the
decimal double double number do not show any
discrepancies in my test cases so far.

BUILD Instructions

1. Install FTN95 Personal Edition on your Windows
   or Linux system (with Wine). The installer is
   ft95_personal.exe and may be downloaded from
   the website,

   https://www.silverfrost.com/32/ftn95/ftn95_personal_edition.aspx

   Note that this is a trial version for personal use
   or evaluation. If you are installing on a recent
   Linux system with Wine, configure Wine to emulate
   Windows 11 and turn off the annoying Wine debug
   messages.

   For Linux/Wine users, you can use the command
   $ wine ft95_personal.exe


2. Compile the .f90 files from the command line. I
   assume you can do this from Windows Powershell, but
   I have only done it from Wine under Linux.

   $ wine ftn95 ddfuna.f90
   $ wine ftn95 ddfune.f90
   $ wine ftn95 ddmodule.f90
   $ wine ftn95 second.f90
   $ wine ftn95 testddfun.f90

   Windows users omit 'wine' in the above commands.
   You will see some warnings and comments but the 
   files provided here should not give any compilation 
   errors. The compiler will generate .obj files and
   for modules, it will also generate .MOD files.

3. Link the object files using slink.exe to build the
   program testddfun.exe

   $ wine slink testddfun.obj ddfuna.obj ddfune.obj ddmodule.obj\
     second.obj -file:testddfun.exe

   At this point, you will have a console Win32 application,
   testddfun.exe

4. Run the testddfun.exe program

   $ wine testddfun

   A popup window will appear for a few seconds displaying
   the trial version message and then disappear, after
   which the program will run.

   An 'ERROR' will be indicated for those results which
   do not match the expected precision given in the file,

   testddfun.ref.txt