! a_timing.f90
!
! This is the pattern for making timing measurements of small to
! medium hunks of code. Long running code that takes over 10 seconds
! can usually be measured directly.
! Fill in a subroutine or function or direct code you want to time,
! where indicated by the comments.
!
! 11/7/96 JSS adapted from ACM SIGAda Performance Issues Working Group
!
program a_timing
  use iteration
  implicit none
  real :: cpu_time           ! actually "wall" time in seconds
  real :: tolerance          ! tolerance on measurement in seconds
  real :: feature_time       ! time for one execution of the feature
  real :: executions         ! number of time feature executed
  integer, parameter :: check_times = 1000   ! inside loop check
  integer :: iteration_count ! outer loop count set and varied by iteration
  logical :: stable          ! the timing seems to be OK
  integer :: outer           ! loop variable
  integer :: inner           ! loop variable
  real    :: a               ! scratch variable

  print *, "a_timing example -- your title goes here --"

  call initialize(iteration_count, check_times)
  do
    ! calibrate a control time that accounts for loop and timing overhead
    call start_control
    do outer=1,iteration_count
      global = 0
      do inner=1,check_times
        call increment(global)
      end do
    end do
    call stop_control

    ! run the actual test in the same construct that was calibrated
    a = 1.0                      ! misc initialization here
    call start_test
    do outer=1,iteration_count
      global = 0
      do inner=1,check_times
        a = a*sin((1.0+a))
        call increment(global)
      end do
    end do
    call stop_test
    call test_stable(iteration_count, stable)
    if (stable) exit
  end do
  if (a == huge(a)) print *, "strange"  ! you must use computed variables
                                        ! in an "if" test to keep them from
                                        ! being optimized away
  call feature_times(cpu_time, tolerance, feature_time, executions)
  print *, "feature time=", feature_time, "  seconds +/-", tolerance
  print *, "total test time=", cpu_time,  "  executions=", executions

end program a_timing