Steady_State

Provides methods for detecting steady-state conditions based on t-test.

Examples

The following example demonstrates some of the methods found in the benchmark_steady_state module.

   use benchmark_steady_state, only: ssd
   use benchmark_workflow, only: workflow
   use benchmark_options
   use benchmark_method
   use benchmark_timer, only: clock
   use benchmark_statistics, only: stats   
   use benchmark_warning, only: display_maxcall_warning
   use benchmark_string
   use benchmark_kinds
   use benchmark_output_unit
 
   class(benchmark_run), intent(inout) :: step
   !private
   integer :: k
   real(r8) :: start, finish
   type(stats) :: s
   real(r8), allocatable :: times(:)
   real(r8) :: treshold
      
      
   maxcall_reached = .false.
   treshold = step%options%ssd_threshold
   if (first_call)  write (output_unit, '(A)') new_line('A'), step%header, new_line('A')
 
   step%options%count = step%options%count + 1
   allocate(times(step%options%sampling_window), source=0.0_r8)
   block
      integer     :: icount, jcount, count
      real(r8)    :: crit, t
      
      crit = 0.0_r8; icount = 0; jcount = 0; count = 0
      call clock(start)
      do while (crit <= (1.0_r8 - treshold))
         call step%method%invoke(); call clock(finish)
         t = finish - start
         icount = icount + 1
         if (t > step%options%mintime) then 
               times(1 + modulo(jcount, step%options%sampling_window)) =   &
                  t / real(icount, r8)
               jcount = jcount + 1
               
               if (jcount >= step%options%sampling_window) crit =          &
                  ssd(times, modulo(jcount, step%options%sampling_window), &
                  treshold)
               
               icount = 0
               call clock(start)
         end if
         count = count + 1
 
         if (count >= step%options%maxcalls) then 
               maxcall_reached = .true.
               display_maxcall_warning = .true.
               exit
         end if
      end do
   end block
 
   call s%compute(times)
   if (step%options%csv_unit /= 0) then
      call summary(step, s, step%options%csv_unit)
   else
      call summary(step, s)
   end if
   deallocate(times)
   nullify(step%method)
   nullify(step%options)

Remarks

The steady-state detection algorithm is based on the work by J. D. Kelly and J. D. Hedengren, “A steady-state detection (SSD) algorithm to detect non-stationary drifts in processes,” J. Process Control, vol. 23, no. 3, pp. 326–331, 2013. The original algorithm has been altered to be used with dynamic real-time data.