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"""Implements the FirstReaction class."""
from Solver import Solver
from Event import makeTriggerTimeEvent
import heapq
import random
class FirstReaction(Solver):
def __init__(self, model, maxSteps):
Solver.__init__(self, model, maxSteps)
def initialize(self):
# Initialize the state.
Solver.initialize(self)
# Compute the initial propensities and the initial time to the first
# reaction.
self.computeTimeToFirstReaction()
def simulate(self, endTime):
while(self.step(endTime)):
pass
def step(self, endTime):
reactionTime = self.model.time + self.timeToFirstReaction
# The time at the end of the next step or frame.
tau = min(min(reactionTime, self.eventQueue[0][0]), endTime)
# Check the trigger events.
for e in self.model.triggerEvents.values():
if e.evaluate(tau):
t = self.model.time + e.delay
if e.useValuesFromTriggerTime:
heapq.heappush(self.eventQueue,
(t, makeTriggerTimeEvent(e)))
else:
heapq.heappush(self.eventQueue, (t, e))
# If we have reached the end time.
if (reactionTime > endTime and self.eventQueue[0][0] > endTime):
# Advance the time.
self.timeToFirstReaction -= endTime - self.model.time
self.model.time = endTime
return False
# Check that we have not exceeded the allowed number of steps.
self.incrementStepCount()
# If the reaction happens before the next event.
if reactionTime < self.eventQueue[0][0]:
# Fire the reaction.
self.model.time += self.timeToFirstReaction
self.firstReaction.fire()
else:
# Fire the event.
self.model.time, e = heapq.heappop(self.eventQueue)
e.fire()
# Compute the time to the next reaction.
self.computeTimeToFirstReaction()
return True
def computeTimeToFirstReaction(self):
# Start with infinity.
self.timeToFirstReaction = float('inf')
self.firstReaction = None
for id in self.model.reactions:
r = self.model.reactions[id]
propensity = r.propensity()
if (propensity == 0):
continue
t = random.expovariate(propensity)
if (t < self.timeToFirstReaction):
self.timeToFirstReaction = t
self.firstReaction = r
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