Fatal error LNK1120: 2 unresolved externals

[nnnnn]

********************************************************
Hi , dear friends;
May you please kindly help me with this problem .?
Running my program (fortran90 in compaq visual fortran.6..) leads to this
messages:

((( Linking...
simpson-3.obj : error LNK2001: unresolved external symbol _FERMI@8
simpson-3.obj : error LNK2001: unresolved external symbol _A_INTEGRAL@4
Debug/simpson-3.exe : fatal error LNK1120: 2 unresolved externals
Error executing link.exe. )))
" FERMI " is a function which is used in my program( it is called in the subroutin) .And
" A_INTEGRAL " is a one dimensional array.
What do you suggest ?? I copy the program here (if it helps) .

Best Regards
N. M.
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program INTEG_3Ghaneh

real(8),parameter ::Pi=3.14
real(8),parameter ::Temp=1
REAL(8) ::a,b
Integer :: n !n : an even number
integer :: i,j,i1,i2,i3
real(8) :: NN,mo
complex(8),parameter :: ii = (0, 1)

n = 20
a =-10
b = 10
mo= 1

CALL Simpson(n,a,b)
open(unit=160,file = "out3Ghaneh.txt")

do i=-n/2+1,n/2-1
write(160,*)," Integral = ",a_Integral(i)
enddo
pause
!/////////////////////////////////////////////////////////////
contains
!++++++++++++++++++++++++++++++++++++++++++++++++++++++
!function : fermi !

real(8) function fermi(e,mo)
implicit none
real(8),intent(in) :: mo
complex(8),intent(in) :: e(-n/2:n/2)

if(dreal(e(i)) < mo)then
fermi = 1.
else
fermi = 0.
end if

end function fermi

!////////////////// Simpson Integrals Subroutine /////////////////////////////////////
Subroutine Simpson(n,a,b)
Integer,intent(IN) :: n
Real(8),intent(IN) :: a,b
Real(8) :: delta_e,m !n must be an even number
REAL(8) :: wn(-n/2:n/2),e(-n/2:n/2)
complex(8) :: F(-n/2:n/2,-n/2:n/2,-n/2:n/2,-n/2:n/2)
complex(8) :: a_integral(-n/2:n/2),b_Integral(-n/2:n/2,-n/2:n/2),c_Integral(-n/2:n/2,-n/2:n/2,-n/2:n/2)
real(8), external :: fermi
delta_e = ( b - a )/n

!
! Here you introduce your integrant :
!
NN=fermi(e(i1),mo)*fermi(-e(i2),mo)*fermi(e(i3),mo)+fermi(-e(i1),mo)*fermi(e(i2),mo)*fermi(-e(i3),mo)

do i=-n/2,n/2
wn(i) = (2*i + 1)*Pi*Temp
e(i) = wn(i)
F(i,i1,i2,i3)=NN/(ii*wn(i)-e(i1)+e(i2)-e(i3)) !F(i)=NN/(ii*wn(i)-e(i1)+e(i2)-e(i3))

end do

c_integral(i,i2,i3)=F(i,-n/2,i2,i3)+F(i,n/2,i2,i3)

Do i1=(-n/2)+1,(n/2)-1
m=mod(i1,2)
c_integral(i,i2,i3)=c_integral(i,i2,i3)+2*(1-m)*F(i,i1,i2,i3)+4*m*F(i,i1,i2,i3)

END DO
c_integral(i,i2,i3)=c_integral(i,i2,i3)*delta_e/3
!*********************************************************second fold of Integral************************************
b_integral(i,i3)=c_integral(i,-n/2,i3)+c_integral(i,n/2,i3)

Do i2=(-n/2)+1,(n/2)-1
m=mod(i1,2)
b_integral(i,i3)=b_integral(i,i3)+2*(1-m)*c_integral(i,i2,i3)+4*m*c_integral(i,i2,i3)
END DO
b_integral(i,i3)=b_integral(i,i3)*delta_e/3
!*********************************************************third fold of Integral*************************************
b_integral(i,i3)=c_integral(i,-n/2,i3)+c_integral(i,n/2,i3)
Do i2=(-n/2)+1,(n/2)-1
m=mod(i1,2)
a_integral(i)=a_integral(i)+2*(1-m)*b_integral(i,i3)+4*m*b_integral(i,i3)
END DO
a_integral(i)=a_integral(i)*delta_e/3
!********************************************************************************************************************
END Subroutine Simpson
!/////////////////////////////////////////////////////////////
END program INTEG_3Ghaneh

 

[Mark44]

Is the code you showed in separate files? You are getting linker errors, which means that the linker cannot find the code associated with the symbols _FERMI and _A_INTEGRAL.

It's possible that your configuration file doesn't include all of your source files. Otherwise, I don't see anything obvious.

 

[quicknote]

Hello N.M.,

Thank you for reaching out for help with your program. The error you are receiving, "fatal error LNK1120: 2 unresolved externals," means that the linker was unable to find the definitions for two external symbols, specifically "_FERMI@8" and "_A_INTEGRAL@4." This means that these symbols are being used in your program, but the linker is unable to find where they are defined.

There are a few potential causes for this error. One possibility is that you have not properly declared or defined these symbols in your program. Make sure that you have declared them as external functions or variables before using them. Another possibility is that you are missing a library or module that contains the definitions for these symbols. Make sure that you have included all necessary libraries and modules in your program.

I also noticed that your program contains a subroutine called "Simpson" which is being called in your main program. However, I do not see a definition for this subroutine in your code. Make sure that you have defined this subroutine before calling it in your main program.

I hope this helps to resolve your issue. If you continue to have trouble, I suggest seeking help from a more experienced Fortran programmer or consulting the documentation for your compiler. Good luck with your program!