Time Step Models

Fixed Step Loop

Repeated Updates

A fixed-step loop applies the same update rule for a known number of steps.

Program

Play the program to choose how many repeated updates advance the value.

fixed_step_loop.f90 
program fixed_step_loop_demo
    implicit none
    integer :: step
    integer :: step_count
    real :: dt
    real :: rate
    real :: value

    step_count = 
    dt = 0.5
    rate = 2.0
    value = 10.0
    do step = 1, step_count
        value = value + rate * dt
    end do
    print '(I0, 1X, F0.1)', step_count, value
end program fixed_step_loop_demo

program fixed_step_loop_demo
    implicit none
    integer :: step
    integer :: step_count
    real :: dt
    real :: rate
    real :: value

    step_count = 
    dt = 0.5
    rate = 2.0
    value = 10.0
    do step = 1, step_count
        value = value + rate * dt
    end do
    print '(I0, 1X, F0.1)', step_count, value
end program fixed_step_loop_demo

program fixed_step_loop_demo
    implicit none
    integer :: step
    integer :: step_count
    real :: dt
    real :: rate
    real :: value

    step_count = 
    dt = 0.5
    rate = 2.0
    value = 10.0
    do step = 1, step_count
        value = value + rate * dt
    end do
    print '(I0, 1X, F0.1)', step_count, value
end program fixed_step_loop_demo
fixed step A fixed-step model repeats the same update formula.
loop counter `step` records which update is currently being applied.
accumulated state `value` carries the result from one step into the next.