Fortran dll

[KeesRoos]

Hi all.

I am new to Frotran, need some precise calculations, writing a fortran dll, to be called from C#. Following Fortran function compiles (Intel Fortran compiler, Microsoft Visual studio 2022) without error or warning:

function getSin( instance ) result(output)

! Dec$ ATTRIBUTES DLLEXPORT, C :: getSin

!Dec$ ATTRIBUTES REFERENCE :: instance

type(struct_angle), intent(in) :: instance

real*16 :: output

real*16 :: angle16

real*16 :: sine16

angle16 = instance%value_

sine16 = QSIN(angle16)

output = angle16

end function getSin

However, C# reports an error: cannot find the module or dependencies.

When I comment out the line: sine16 = QSIN(angle16)

and let the function return a fictive value, the problem does not occur.

Can anyone tell what causes this error and what I can do to solve it? 

[Steve_Lionel]

See Solved: Re: C++ main cannot load Fortran DLL that has ALLOCATE statements - Intel Community , though in your case it is probably libmmd.dll.

[JohnNichols]

function getSin( instance ) result(output)
! Dec$ ATTRIBUTES DLLEXPORT, C :: getSin
 
!Dec$ ATTRIBUTES REFERENCE :: instance
 
type(struct_angle), intent(in) :: instance
real*16 :: output
 
real*16 :: angle16
real*16 :: sine16
 
angle16 = instance%value_
sine16 = QSIN(angle16)
 
output = angle16
end function getSin

It helps make it easy to read if you use the formatting tool on the tool bar it looks like </>.

In reality, there is almost a one to one correspondence between Fortran and C# in terms of functionality, so making a DLL in Fortran unless you are doing heavy duty calculations is a waste of time, unless it is a learning exercise.  

[JohnNichols]

As an example the Numerical Analysis in Fortran FFT translated into C# yields the same loop time on 16384 data points as Fortran version,  and the version on RPi runs in 7 seconds.  

Of course one can use the MKL version, which is faster. 

Mixing languages is painful.  I was running some numerically intensive Fortran stuff the other day, the loop time for each set was about 1.5 seconds on a core I7, the machine started some services and the loop time went to 5 seconds, it took me a while to find the blasted services and turn them off.  

[KeesRoos]

Hi Steve,

thanks for your prompt reaction. I have been out this week, just home again.

Adding oneAPI\2025.0\bin to the Path variable does not solve my problem.

Any idea what more I can try? 

[Steve_Lionel]

If you open an Intel oneAPI command prompt window (from the Start menu) and run your application from there, does it work? Did you build your DLL as a Release configuration?