Timers in Fortran

Our first example demonstrates the use of timers in Fortran. We’ll use the sleep subroutine from the iso_c_binding module to simulate timers.

program timers
    use iso_c_binding, only: c_sleep
    implicit none
    
    ! Simulate a timer that waits for 2 seconds
    call timer1()
    
    ! Simulate a timer that can be cancelled
    call timer2()
    
contains

    subroutine timer1()
        integer :: result
        
        ! Wait for 2 seconds
        result = c_sleep(2)
        print *, "Timer 1 fired"
    end subroutine timer1
    
    subroutine timer2()
        integer :: result
        logical :: stop_timer
        
        stop_timer = .true.
        
        if (stop_timer) then
            print *, "Timer 2 stopped"
        else
            ! This part would run if the timer wasn't stopped
            result = c_sleep(1)
            print *, "Timer 2 fired"
        end if
        
        ! Wait for 2 seconds to show that Timer 2 doesn't fire
        result = c_sleep(2)
    end subroutine timer2
    
end program timers

In this Fortran program:

1. We use the iso_c_binding module to access the c_sleep function, which allows us to pause the program execution.

2. The timer1 subroutine simulates a timer that waits for 2 seconds using c_sleep(2).

3. The timer2 subroutine demonstrates a timer that can be cancelled. We use a logical variable stop_timer to simulate stopping the timer.

4. In the main program, we call both timer1 and timer2.

To run the program:

$ gfortran timers.f90 -o timers
$ ./timers
Timer 1 fired
Timer 2 stopped

The output shows that Timer 1 fires after 2 seconds, while Timer 2 is stopped before it has a chance to fire.

Note that Fortran doesn’t have built-in timer or ticker features like some other languages. In real-world applications, you might use system-specific libraries or more advanced timing modules for precise timing operations.