Why is My Fortran Code Not Working?

[Petar Mali]

I'm new in programing. Does enybody knows why this don't work.

implicit none
integer i,N,Ntot,istag
real*8 t,U,tpin,k,eg,mstag
real*8 rho,Umstag,Urho
real*8 eaf,eaftot,lambdaminus

write(6,*) 'N,Ntot,t,U'
read (5,*) N,Ntot,t,U
write(36,*) Ntot/2+1

tpin=8.d0*datan(1.do)/dfloat(N)
rho=dfloat(Ntot)/dfloat(N)
Urho=U*rho/2.do

do 1000 istag,Ntot,2

mstag=dfloat(istag)/dfloat(N)
Umstag=U*mstag/2.do

eaftot=0.do
do 200,i=-Ntot/4+1,Ntot/4
k=tpin*dfloat(i)
ek=-2.do*t*dcos(k)
lambdaminus=-dsqrt(ek*ek+Umstag*Umstag)
lambdaminus=lambdaminus+Urho
eaftot=eaftot+lambdaminus
200 continue
eaftot=2.do*eaftot/dfloat(N)-U*(rho*rho-mstag*mstag)/4.do

write(36,990)
990 format(i6,f16.6)

1000 continue
end

 

[jtbell]

Please define "this don't work". What is it supposed to do and what does it actually do? What error messages do you get, if any, and when? (when you try to compile the program, or when you try to run it?)

 

[AlephZero]

Your constants like 2.do should be 2.d0 (with a zero, not a letter o).

If that doesn't fix your problem ... what [STRIKE]Christo[/STRIKE] JT Bell said.

 

[Petar Mali]

Tnx. That was mistake.

 

[LudusRex]

It is difficult to determine the exact issue without more information or a specific error message. However, some potential problems with the code could be:

1. The use of implicit none is not consistent throughout the code. It is recommended to use it at the beginning of the code to avoid any unintended implicit declarations.

2. The use of real*8 is not a standard way of declaring real variables in Fortran. It is recommended to use the intrinsic function "kind" to specify the desired precision, for example: real(kind=8) t, U, tpin, k, eg, mstag, rho, Umstag, Urho, eaf, eaftot, lambdaminus.

3. The code does not include any comments or explanations of what each section is supposed to do. This can make it difficult for others to understand and debug the code.

4. The code includes non-standard functions such as dfloat and datan. It is recommended to use the standard Fortran functions such as real, double precision, and atan instead.

5. The code does not include any error handling or checks for invalid input values. This could lead to unexpected results or crashes.

6. The do loop at line 20 (do 1000 istag,Ntot,2) appears to have a typo, as the variable "istag" is not defined anywhere in the code. It is recommended to use a variable that has been previously defined or to declare "istag" as an integer.

Overall, it is important to carefully review and test the code, and to consult with more experienced programmers or resources for assistance in troubleshooting any issues.