Passing Arguments between Soubroutines - INFINIT RESULT

[Master_Fortran]

Dears,

I don't know what I forgot, but I tryied to reproduce a problem I'm facing, which is resulting in na infinity result of:  1.713457071104324E+124. I don't know what is wrong with it

I'm trying to pass arguments through subroutines. See the code below. Could you help me please?

program principal

double precision x, y, z, k, w

x = 1;

y = 1;

z = 1;

call soma(x,y,z)

call multiplica(k,w)

write(*,*) "The value of w is: ", w

end program

subroutine soma(a,b,c)

double precision, intent(in) :: a,b

double precision, intent(out) :: c

c = a+b

end subroutine

subroutine multiplica(d,e)

double precision, intent(in) :: d

double precision, intent(out) :: e

double precision x,y,z

call soma(x,y,z)

e = z*d

end subroutine

[DavidWhite]

In your multiplica routine, the variables x and y have not been initialized.

There is no implicit global sharing of variables in Fortran.  You need to share the variables via a module, pass them as arguments, or have the subroutine CONTAINed within the program that declares the variables.

[Master_Fortran]

Thank you David, for your attention. Sorry, but I'm not undertanding it. See what I did. What's wrong now? The result is: -1.0737418E+08. Thanks again.

module somatorio
    
    implicit none
    
    contains
    
    subroutine soma(a,b,c)
    
        double precision, intent(in) :: a,b
        double precision, intent(out) :: c 
    
        c = a + b    
    
    end subroutine
    
end module  

module multi

use somatorio
    
    implicit none
    
    double precision x,y,z
    
    contains
    
 subroutine multiplica(d,e)
    
    double precision, intent(in) :: d
    double precision, intent(out) :: e   
    
    call soma(x,y,z)
    
    e = z * d
    
 end subroutine 
 
end module 

program principal
    
    use somatorio
    use multi
          
    x = 1;
    y = 1;
    z = 1;
 
    write(*,*) "O valor de e é: ", w
    
end program
    
    

[mecej4]

The "result" that you report is arbitrary and meaningless. It is just garbage left in memory that is being reported as if it a real number.

To find the place where the error occurs, compile using the /check:uninit compiler option and run. You will see something similar to 

forrtl: severe (193): Run-Time Check Failure. The variable \'_PRINCIPAL$W\' is being used without being defined
Image              PC        Routine            Line        Source
soma.exe           003E1098  _MAIN__                    50  soma.f90

It might help if you also add 'IMPLICIT NONE' to each subroutine.

The main program USEs the modules containing the subroutines, but since there are no calls to any subroutines in the main program, none of the subroutine code gets executed. Therefore, even if the variable w had been a module variable that was available to the main program, it would still be undefined unless w was initialized.

[Master_Fortran]

OK Guys.

Now I see where I was failing. 

Thank you all. 

Ewerton.