brewpi/components/sud_forecast.py

from components.plant import Pot
from components.pid import PidFactory
from components.sud import Sud, SudState

# Safety cap so a schedule whose target a step can never actually reach
# (e.g. a "hold" colder than ambient with no active cooling) can't hang the
# simulation forever - the estimate is simply cut off there.
MAX_TICKS = 200000


class SudForecastEstimator:
	"""Predicts how long a Sud schedule will actually take by simulating it
	with the same machinery (and params) the real server's brewpi.py wires
	up - a fresh Pot and temperature controller of the configured pid_type,
	driven through the schedule exactly as tasks/sud.py's SudTask would.

	This is deliberately independent of wall-clock/asyncio time: it just
	iterates dt-sized ticks as fast as the CPU allows (a multi-hour brew
	simulates in well under a second), so it can be run synchronously
	whenever a client needs an estimate - the naive "abs(delta)/rate" model
	the GUI used to compute itself has no way to see the real PID cascade's
	spin-up/settling lag, which is exactly why its estimate drifted so far
	from reality (see README.md's "Forecast vs. actual duration")."""

	def __init__(self, dt, theta_amb, plant_params, pid_type, tempctrl_params, heater_max_power):
		self.dt = dt
		self.theta_amb = theta_amb
		self.plant_params = plant_params
		self.pid_type = pid_type
		self.tempctrl_params = tempctrl_params
		self.heater_max_power = heater_max_power

	def set_ambient_temperature(self, theta_amb):
		self.theta_amb = theta_amb

	def estimate(self, doc, start_theta=None):
		"""Returns (t, theta, final_state, confirm_points): t/theta are
		parallel lists of elapsed simulated seconds and temperature,
		covering doc['steps'] from the start all the way to the end
		(final_state is SudState.DONE), or, in the pathological case of
		a step whose target can never actually be reached, wherever
		MAX_TICKS cut the simulation off.

		A step requiring user confirmation doesn't stop the simulation
		either - a human's response time genuinely can't be forecast,
		so it's modeled as zero delay (auto-confirmed the instant that
		step's hold completes) rather than leaving the estimate stuck
		there forever. confirm_points records every place that
		assumption was made, as (step_index, t) pairs, so the caller
		(tasks/sud.py's SudTask) can correct it once a real
		confirmation actually happens: truncate the forecast at that
		point and splice in a freshly anchored simulation of the
		remaining steps in place of the optimistic guess.

		start_theta defaults to the configured ambient temperature - i.e.
		a cold start, same as the GUI's static estimate."""
		if start_theta is None:
			start_theta = self.theta_amb

		sud = Sud()
		if not sud.load(doc) or not sud.schedule:
			return [0.0], [start_theta], SudState.DONE, []

		pot = Pot(self.dt)
		pot.set_plant_params(self.plant_params)
		pot.set_ambient_temperature(self.theta_amb)
		pot.initial(start_theta)
		tc = PidFactory.create(self.pid_type, self.dt)
		tc.set_params(self.tempctrl_params)
		if hasattr(tc, 'set_model_plant_params'):
			tc.set_model_plant_params(self.plant_params)
		if hasattr(tc, 'set_ambient_temperature'):
			tc.set_ambient_temperature(self.theta_amb)
		tc.set_enabled(True)
		tc.set_theta_ist(pot.get_temperature())
		# Seed the target at start_theta - this tc is a fresh, throwaway
		# instance (unlike the real run's persistent one), so without this
		# its theta_soll_set defaults to 0 until a step pushes its own.
		# Steps without their own 'temperature' (common now that ramping
		# isn't gated by a 'ramp' key - see components/sud.py) rely on
		# inheriting whatever target was already running, which for a
		# schedule starting mid-brew (the dynamic remaining forecast) is
		# start_theta, not 0 - without this, such a schedule's first step
		# would have the simulated controller chase 0 degrees indefinitely,
		# hitting MAX_TICKS and producing a needlessly huge result.
		tc.set_theta_soll(start_theta)

		def on_step_changed(step):
			if step is None:
				return
			params = sud.derive_plant_params(step.get('grain_mass', 0), step.get('water_mass', 0))
			pot.set_plant_params(params)
			if hasattr(tc, 'set_model_plant_params'):
				tc.set_model_plant_params(params)
			if sud.state == SudState.RAMPING and step['temperature'] is not None:
				tc.set_theta_soll(step['temperature'])
				tc.set_heatrate_soll(step['ramp']['rate'])
		sud.set_on_changed('step', on_step_changed)

		t = [0.0]
		theta = [pot.get_temperature()]
		confirm_points = []

		sud.start()
		ticks = 0
		while sud.state != SudState.DONE and ticks < MAX_TICKS:
			if sud.state == SudState.WAIT_USER:
				confirm_points.append((sud.index, t[-1]))
				sud.confirm()
				continue

			pot.process()
			tc.set_theta_ist(pot.get_temperature())
			tc.process()
			pot.set_power(max(0, self.heater_max_power * tc.get_power()))

			if sud.state == SudState.RAMPING:
				if tc.is_holding():
					sud.temp_reached()
			sud.tick(self.dt)

			t.append(t[-1] + self.dt)
			theta.append(pot.get_temperature())
			ticks += 1

		return t, theta, sud.state, confirm_points