update_progress_bar Subroutine

    subroutine update_progress_bar()
    !! Updates and displays the horizontal percentage-based progress bar.
        real :: percentage
    !! The percentage of the task completed.
        integer :: filled_length
    !! Length of the filled portion of the progress bar.
        character(len=progress_bar_width) :: bar
    !! The progress bar string.
        integer :: int_percentage
    !! Integer percentage value.

        if (total_calls == 0 .or. .not. show_progress) return  ! Avoid division by zero and check the flag

        percentage = real(completed_calls) / real(total_calls) * 100.0

        ! Ensure percentage does not exceed 100%
        if (percentage > 100.0) percentage = 100.0

        ! Calculate integer percentage
        int_percentage = int(percentage)

        ! Update progress bar only when percentage increases by at least 1%
        if (int_percentage > last_percentage) then
            last_percentage = int_percentage

            ! Calculate the filled length of the progress bar
            filled_length = min(int(percentage / 100.0 * progress_bar_width), progress_bar_width)

            ! Construct the progress bar string
            bar = repeat('=', filled_length)
            if (filled_length < progress_bar_width) then
                bar = bar//'>'//repeat(' ', progress_bar_width - filled_length - 1)
            end if

            ! Print the progress bar and integer percentage
            write (*, '(A, F4.1, A)', advance='no') carriage_return//'['//bar//'] ', percentage, '%'
            call flush (0)  ! Ensure output is displayed immediately
        end if
    end subroutine update_progress_bar