Introduction to Fortran Programming. - Module -

Transcription

1 Introduction to Fortran Programming - Module -

2 Subprograms Subprograms are used to split program into separate smaller units. Internal subprograms are dependent parts of program. Fortran 90 has two types of subprograms: Functions and subroutines. Once each piece is working correctly, we can put the pieces together to build the program.

3 Program unit It is a physically complete sequence of program lines with end statement. Main program: The main program unit containing the first statement of the actual program. External subprogram: User-defined subprogram which is an independent program unit. Module (since Fotran90): A program unit which contains only declarations and external subprograms.

4 Program unit Main program ( program-name ) Internal functions Internal subroutines External Subprograms External functions External subroutines Module Today s topic!!

5 Module Module is a program unit that declares functions, subroutines, and shared variables together. Once of the functions added in Fortran 90. In Fortran90, it is recommended to use modules instead of external subprograms.

6 Module module Module_name [Specification part] contains [Defined function/subroutine] end module Module_name A non-executable statement Declare variables you want to share here. How to write functions and subroutines as usual!!

7 Use statement use Module_name A program module is made accessible to the various program units via use statement. Note that there are restrictions on variable reference. module testmod end module testmod program examp use testmod end program examp The module declaration is in front of the program to use. Write use statement before. Specify necessary modules in the use statement.

8 Compiling modules testmod.f90 module testmod contains end module main.f90 program main use testmod stop end program main Write the module name first. gfortran testmod.f90 main.f90

9 Example 1 Let r be a double-precision real type variable and adding a value appropriately. Create a module with functions and subroutines that calculate the volume of the sphere with radius r.

10 Example 1 volmod.f90 module volmod contains function dvolfunc(r) result(v) real(8) :: pi = acos(-1d0) real(8) :: V end function dvolfunc subroutine dvolsub(r,v) real(8) :: pi = acos(-1d0) real(8), intent(out) :: V end subroutine dvolsub end module volmod main.f90 program vol use volmod real(8) :: r, V r = 2d0 V = dvolfunc(r) call dvolsub(r,v) stop end program vol

11 Example 1 volmod.f90 module volmod contains function dvolfunc(r) result(v) real(8) :: pi = acos(-1d0) real(8) :: V end function dvolfunc subroutine dvolsub(r,v) real(8) :: pi = acos(-1d0) real(8), intent(out) :: V end subroutine dvolsub end module volmod main.f90 program vol use volmod real(8) :: r, V r = 2d0 V = dvolfunc(r) call dvolsub(r,v) stop end program vol Let s refer to pi in main program.

12 Example 1 volmod.f90 module volmod contains function dvolfunc(r) result(v) real(8) :: pi = acos(-1d0) real(8) :: V end function dvolfunc subroutine dvolsub(r,v) real(8) :: pi = acos(-1d0) real(8), intent(out) :: V end subroutine dvolsub end module volmod main.f90 program vol use volmod real(8) :: r, V r = 2d0 V = dvolfunc(r) call dvolsub(r,v) write(*,*) pi stop end program vol Let s refer to pi in main program. Error This is not possible.

13 Example 1 volmod.f90 module volmod real(8) :: pi = acos(-1d0) contains function dvolfunc(r) result(v) real(8) :: V end function dvolfunc subroutine dvolsub(r,v) real(8), intent(out) :: V end subroutine dvolsub end module volmod main.f90 program vol use volmod real(8) :: r, V r = 2d0 V = dvolfunc(r) Let s refer to pi in main program. Declare pi here. call dvolsub(r,v) write(*,*) pi stop end program vol Pi is the shared valiable Now it is possible.

14 Example 1 volmod.f90 module volmod real(8) :: pi = acos(-1d0) contains function dvolfunc(r) result(v) real(8) :: V end function dvolfunc subroutine dvolsub(r,v) real(8), intent(out) :: V end subroutine dvolsub end module volmod main.f90 program vol use volmod real(8) :: r, V r = 2d0 V = dvolfunc(r) pi = 0d0 call dvolsub(r,v) Let s refer to pi in main program. Declare pi here. write(*,*) pi stop end program vol Pi is the shared valiable Change the value of pi. Returning the wrong answer as pi was changed.

15 Example 1 volmod.f90 module volmod real(8),parameter :: pi = acos(-1d0) contains function dvolfunc(r) result(v) Declare pi as parameter real(8) :: V attribute. end function dvolfunc subroutine dvolsub(r,v) real(8), intent(out) :: V end subroutine dvolsub end module volmod main.f90 program vol use volmod real(8) :: r, V r = 2d0 V = dvolfunc(r) pi = 0d0 call dvolsub(r,v) write(*,*) pi stop end program vol Let s refer to pi in main program. Error Since pi is the parameter attribute. When trying to change, Error!

16 Example 2 Let r be a double-precision real type valiable of a onedimensional array and substitute a value appropriately. Add the function and subroutine that calculate the volume of the sphere with radius r to the module written in Example 1.

17 Example 2 module volmod real(8), parameter :: pi = acos(-1d0) contains function dvolfunc(r) result(v) real(8) :: V end function dvolfunc function dmvolfunc(r) result(v) (:) real(8) :: V(size(r)) end function dmvolfunc (Continue to the right ) subroutine dvolsub(r,v) real(8), intent(out) :: V end subroutine dvolsub subroutine dmvolsub(r,v) (:) real(8),intent(out) ::V(size(r)) end subroutine dmvolsub end module volmod

18 Example 2 Function / subroutine name should be different! Array declaration is the same as for internal functions! (Continue to the right) Array declaration is the same as for internal functions!

19

20

21

22

23