Timers

The package provides the following functions:

tic()
Starts a timer

toc(prn=true)
Print the time in seconds since tic() was called. To suppress the printed output use toc(false).

Returns the time since the timer was started in seconds.

sleep_ms(time_ms)
Sleeps for the given number of milli-seconds. Accuracy on Linux better than 100 nanoseconds +-0.2%, but only if the system is not fully loaded. On Linux for delays larger than 10ms sleep() is used, on Windows for delays larger than 16 ms.

wait_until(finish_ns; always_sleep=false)
Sleeps until the given time [ns] is reached. Example:

dt = 0.05
start = time_ns()
for i in 1:100
    # do some work
    wait_until(start + i*dt*1e9)
end

The section "# do some work" is executed exactly every 50ms as long as executing this section takes less than 50ms.

The additional parameter always_sleep can be set to true if you want to ensure that the sleep function is always called for at least 1 ms. This is useful if you need to ensure that cooperative multitasking works even for the price to miss the deadline.

Comparison of the desired and actual sleep time for the functions sleep() and sleep_ms():

OS: Ubuntu 18.04 with a i7-7700K CPU and the standard kernel version 5.4.0-87-generic.

julia> include("test/bench.jl")
7-element BenchmarkTools.BenchmarkGroup:
  tags: ["sleep_ms"]
  "100µs" => TrialEstimate(100.152 μs)
  "200µs" => TrialEstimate(200.108 μs)
  "5ms" => TrialEstimate(5.000 ms)
  "1ms" => TrialEstimate(1.000 ms)
  "10ms" => TrialEstimate(10.001 ms)
  "500µs" => TrialEstimate(500.093 μs)
  "2ms" => TrialEstimate(2.000 ms)
4-element BenchmarkTools.BenchmarkGroup:
  tags: ["sleep"]
  "20ms" => TrialEstimate(21.267 ms)
  "5ms" => TrialEstimate(6.255 ms)
  "1ms" => TrialEstimate(2.219 ms)
  "10ms" => TrialEstimate(11.215 ms)
  "2ms" => TrialEstimate(3.199 ms)

This are the mean values. The error of the sleep_ms function is below 0.1% +- 100ns. The error of the default sleep() function of Julia on Linux is between 1ms and 2ms, for the set values of 1ms to 10ms this is an error of 13% to 62%. On Windows the error is between 10ms and 20ms.