path: root/unit_trace/viz/schedule.py

#!/usr/bin/env python

"""The data structures to store a schedule (task system), along with all
the job releases and other events that have occurred for each task. This gives
a high-level representation of a schedule that can be converted to, say, a
graphic."""

from draw import *
import util

import copy

EVENT_LIST = None
SPAN_EVENTS = None

class TimeSlotArray(object):
    """Represents another way of organizing the events. This structure organizes events by
    the (approximate) time at which they occur. Events that occur at approximately the same
    time are assigned the same ``slot'', and each slot organizes its events by task number
    as well as by CPU."""
    
    TASK_LIST = 0
    CPU_LIST = 1
    
    def __init__(self, time_per_maj=None, num_tasks=0, num_cpus=0):
        if time_per_maj is None:
            self.array = None
            return
            
        self.time_per_maj = time_per_maj
        self.list_sizes = { TimeSlotArray.TASK_LIST : num_tasks, TimeSlotArray.CPU_LIST : num_cpus }
        self.array = {}
        
        for type in self.list_sizes:
            num = self.list_sizes[type]
            self.array[type] = []
            for j in range(0, num):
                # for each slot in the array, we need a list of all events under this type
                # (for example, a list of all events that occur in this time slot, indexed
                # by task).
                self.array[type].append(dict(zip(EVENT_LIST, \
                                [{} for j in range(0, len(EVENT_LIST))])))
    
    def get_time_slot(self, time):
        return int(time // self.time_per_maj)
    
    def _put_event_in_slot(self, list_type, no, klass, slot, event):
        if slot not in self.array[list_type][no][klass]:
            self.array[list_type][no][klass][slot] = []
        self.array[list_type][no][klass][slot].append(event)
                
    def add_event_to_time_slot(self, event):
        task_no = event.get_job().get_task().get_task_no()
        cpu = event.get_cpu()
        time_slot = self.get_time_slot(event.get_time())
        
        self._put_event_in_slot(TimeSlotArray.TASK_LIST, task_no, event.__class__, time_slot, event)
        self._put_event_in_slot(TimeSlotArray.CPU_LIST, cpu, event.__class__, time_slot, event)
        
        if event.__class__ in SPAN_END_EVENTS:
            self.fill_span_event_from_end(event)
        
    def fill_span_event_from_end(self, event):
        start_slot = None
        if event.corresp_start_event is None:
            start_slot = self.get_time_slot(event.get_job().get_task().get_schedule().start) - 1
        else:
            start_slot = self.get_time_slot(event.corresp_start_event.get_time())
        end_slot = self.get_time_slot(event.get_time())
        
        for slot in range(start_slot + 1, end_slot):
            task_no = event.get_job().get_task().get_task_no()
            cpu = event.get_cpu()
            
            dummy = SPAN_END_EVENTS[event.__class__](task_no, cpu)
            dummy.corresp_start_event = event.corresp_start_event
            dummy.corresp_end_event = event
                    
            self._put_event_in_slot(TimeSlotArray.TASK_LIST, task_no, dummy.__class__, slot, dummy)
            self._put_event_in_slot(TimeSlotArray.CPU_LIST, cpu, dummy.__class__, slot, dummy)
            
    def fill_span_event_from_start(self, event):
        end_slot = None
        if event.corresp_end_event is None:
            end_slot = self.get_time_slot(event.get_job().get_task().get_schedule().end) + 1
        else:
            end_slot = self.get_time_slot(event.corresp_end_event.get_time())
        start_slot = self.get_time_slot(event.get_time())
        
        for slot in range(start_slot + 1, end_slot):
            task_no = event.get_job().get_task().get_task_no()
            cpu = event.get_cpu()
            
            dummy = SPAN_START_EVENTS[event.__class__](task_no, cpu)
            dummy.corresp_start_event = event
            dummy.corresp_end_event = event.corresp_end_event
            
            self._put_event_in_slot(TimeSlotArray.TASK_LIST, task_no, dummy.__class__, slot, dummy)
            self._put_event_in_slot(TimeSlotArray.CPU_LIST, cpu, dummy.__class__, slot, dummy)
            
    def iter_over_period(self, start, end, start_no, end_no, list_type, event_types):
        if self.array is None:
            return # empty schedule
            
        if start > end:
            raise ValueError('Litmus is not a time machine')
        if start_no > end_no:
            raise ValueError('start no should be less than end no')
        
        start_slot = self.get_time_slot(start)
        end_slot = self.get_time_slot(end) + 2
        
        start_no = max(0, start_no)
        end_no = min(self.list_sizes[list_type] - 1, end_no)
        
        for no in range(start_no, end_no + 1):
            for type in event_types:
                for slot in range(start_slot, end_slot):
                    if slot in self.array[list_type][no][type]:
                        for event in self.array[list_type][no][type][slot]:
                            yield event
    
class Schedule(object):
    """The total schedule (task system), consisting of a certain number of
    tasks."""
    
    def __init__(self, name, num_cpus, task_list=[]):
        self.name = name
        self.tasks = {}
        self.task_list = []
        self.selected = {}
        self.time_slot_array = None
        self.cur_task_no = 0
        self.num_cpus = num_cpus
        for task in task_list:
            self.add_task(task)
    
    def get_selected(self):
        return self.selected
        
    def set_selected(self, new_selected):
        for event in self.selected:
            event.selected = False
        for event in new_selected:
            event.selected = True
        self.selected = new_selected
    
    def get_selected(self):
        return copy.copy(self.selected)
            
    def set_time_params(self, time_per_maj=None):
        self.time_per_maj = time_per_maj
        if self.time_per_maj is None:
            self.time_slot_array = TimeSlotArray()
            return
            
        self.time_slot_array = TimeSlotArray(self.time_per_maj, \
                                                 len(self.task_list), self.num_cpus)
            
    def get_time_slot_array(self):
        return self.time_slot_array
    
    def get_time_bounds(self):
        return (self.start, self.end)
        
    def scan(self, time_per_maj):
        self.start = None
        self.end = None
        
        self.set_time_params(time_per_maj)
        
        # we scan the graph task by task, and job by job
        for task_no, task in enumerate(self.get_task_list()):
            switches = {}
            for event in EVENT_LIST:
                switches[event] = None
            cur_cpu = [Event.NO_CPU]
            for job_no in sorted(task.get_jobs().keys()):
                job = task.get_jobs()[job_no]    
                for event_time in sorted(job.get_events().keys()):
                    # could have multiple events at the same time (unlikely but possible)
                    for event in job.get_events()[event_time]:
                        event.scan(cur_cpu, switches)
                        
            # What if one of the initial "span events" (switch to or inversion starting) never got a
            # corresponding end event? Well, then we assume that the end event was simply outside of
            # the range of whatever we read in. So we need to fill dummies starting from the initial
            # event all the way to the end of the graph, so that the renderer can see the event no matter
            # how far the user scrolls to the right.
            for span_event in SPAN_START_EVENTS:
                event = switches[span_event]
                if event is not None:
                    self.time_slot_array.fill_span_event_from_start(event)
        
    def add_task(self, task):
        if task.name in self.tasks:
            raise ValueError("task already in list!")
        self.tasks[task.name] = task
        self.task_list.append(task)
        task.schedule = self
        task.task_no = self.cur_task_no
        self.cur_task_no += 1
    
    def get_tasks(self):
        return self.tasks
        
    def get_task_list(self):
        return self.task_list
    
    def get_name(self):
        return self.name
    
    def get_num_cpus(self):
        return self.num_cpus
                    
class Task(object):
    """Represents a task, including the set of jobs that were run under
    this task."""
    
    def __init__(self, name, job_list=[]):
        self.name = name
        self.jobs = {}
        self.task_no = None
        self.schedule = None
        for job in job_list:
            self.add_job(job)
        
    def add_job(self, job):
        if job.job_no in self.jobs:
            raise ScheduleError("a job is already being released at this time for this task")
        self.jobs[job.job_no] = job
        job.task = self
    
    def get_schedule(self):
        return self.schedule
        
    def get_jobs(self):
        return self.jobs
    
    def get_task_no(self):
        return self.task_no
        
    def get_name(self):
        return self.name
            
class Job(object):
    """Represents a job, including everything that happens related to the job"""
    def __init__(self, job_no, event_list=[]):
        self.job_no = job_no
        self.events = {}
        self.task = None
        for event in event_list:
            self.add_event(event)
        
    def add_event(self, event):
        if event.time not in self.events:
            self.events[event.time] = []
        self.events[event.time].append(event)
        event.job = self
    
    def get_events(self):
        return self.events
    
    def get_task(self):
        return self.task
    
    def get_job_no(self):
        return self.job_no

class DummyEvent(object):
    """Represents some event that occurs, but might not actually be
    a full-fledged ``event'' in the schedule. It might instead be a dummy
    event added by the application to speed things up or keep track of
    something. Such an event won't be added to the schedule tree, but
    might appear in the time slot array."""

    def __init__(self, time, cpu):
        self.time = time
        self.cpu = cpu
        self.job = None
        self.layer = None
    
    def __str__(self):
        return '[Dummy Event]'
            
    def get_time(self):
        return self.time
        
    def get_cpu(self):
        return self.cpu
        
    def get_job(self):
        return self.job
    
    def get_layer(self):
        return self.layer
        
    def render(self, graph, layer, prev_events, selectable=False):
        """Method that the visualizer calls to tell the event to render itself
        Obviously only implemented by subclasses (actual event types)
        
        ``Rendering'' can mean either actually drawing the event or just
        adding it as a selectable region. This is controlled by the
        ``selectable'' parameter"""
        raise NotImplementdError
        
class Event(DummyEvent):
    """Represents an event that occurs while a job is running (e.g. get scheduled
    on a CPU, block, ...)"""
    NO_CPU = -1
    NUM_DEC_PLACES = 2
    
    def __init__(self, time, cpu):
        super(Event, self).__init__(time, cpu)
        self.erroneous = False
        self.selected = False
    
    def __str__(self):
        return '[Event]'
    
    def _common_str(self):
        job = self.get_job()
        task = job.get_task()
        return ' for task ' + str(task.get_name()) + ': (TASK, JOB)=' + str((task.get_task_no(), \
            job.get_job_no())) + ', CPU=' + str(self.get_cpu())
            
    def is_erroneous(self):
        """An erroneous event is where something with the event is not quite right,
        something significantly wrong that we don't have logical information telling
        us how we should render the event."""
        return self.erroneous
    
    def is_selected(self):
        """Returns whether the event has been selected by the user. (needed for rendering)"""
        return self.selected
            
    def scan(self, cur_cpu, switches):
        """Part of the procedure that walks through all the events and sets
        some parameters that are unknown at first. For instance, a SwitchAwayEvent
        should know when the previous corresponding SwitchToEvent occurred, but
        the data does not tell us this, so we have to figure that out on our own
        by scanning through the events. ``cur_cpu'' gives the current CPU at this
        time in the scan, and ``switches'' gives the last time a certain switch
        (e.g. SwitchToEvent, InversionStartEvent) occurred"""
        time = self.get_time()
        sched = self.get_job().get_task().get_schedule()
        if sched.start is None or time < sched.start:
            sched.start = time
        if sched.end is None or time > sched.end:
            sched.end = time
        
        sched.get_time_slot_array().add_event_to_time_slot(self)

class ErrorEvent(Event):
    pass
                
class SuspendEvent(Event):
    def __init__(self, time, cpu):
        super(SuspendEvent, self).__init__(time, cpu)
        self.layer = Canvas.MIDDLE_LAYER
    
    def __str__(self):
        return 'Suspend' + self._common_str() + ', TIME=' + util.format_float(self.get_time(), Event.NUM_DEC_PLACES)
            
    def scan(self, cur_cpu, switches):
        if self.get_cpu() != cur_cpu[0]:
            self.erroneous = True
            #fprint "suspending on a CPU different from the CPU we are on!"
        super(SuspendEvent, self).scan(cur_cpu, switches)
            
    def render(self, graph, layer, prev_events, selectable=False):
        if layer == self.layer:
            prev_events[self] = None
            if selectable:
                graph.add_sel_suspend_triangle_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                                self.get_cpu(), self)
            else:
                graph.draw_suspend_triangle_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                                self.get_cpu(), self.is_selected())
            
        
class ResumeEvent(Event):
    def __init__(self, time, cpu):
        super(ResumeEvent, self).__init__(time, cpu)
        self.layer = Canvas.MIDDLE_LAYER
    
    def __str__(self):
        return 'Resume' + self._common_str() + ', TIME=' + util.format_float(self.get_time(), Event.NUM_DEC_PLACES)
            
    def scan(self, cur_cpu, switches):
        if cur_cpu[0] != Event.NO_CPU and cur_cpu[0] != self.get_cpu():
            self.erroneous = True
            #print "Resuming when currently scheduled on a CPU, but on a different CPU from the current CPU!"
        super(ResumeEvent, self).scan(cur_cpu, switches)
        
    def render(self, graph, layer, prev_events, selectable=False):
        if layer == self.layer:
            prev_events[self] = None
            if selectable:
                graph.add_sel_resume_triangle_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                                self.get_cpu(), self)
            else:
                graph.draw_resume_triangle_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                               self.get_cpu(), self.is_selected())
                
        
class CompleteEvent(Event):
    def __init__(self, time, cpu):
        super(CompleteEvent, self).__init__(time, cpu)
        self.layer = Canvas.TOP_LAYER
    
    def __str__(self):
        return 'Complete' + self._common_str() + ', TIME=' + util.format_float(self.get_time(), Event.NUM_DEC_PLACES)
            
    def scan(self, cur_cpu, switches):
        super(CompleteEvent, self).scan(cur_cpu, switches)
    
    def render(self, graph, layer, prev_events, selectable=False):
        if layer == Canvas.TOP_LAYER:
            prev_events[self] = None
            if selectable:
                graph.add_sel_completion_marker_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                                self.get_cpu(), self)
            else:
                graph.draw_completion_marker_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                                 self.get_cpu(), self.is_selected())

class SwitchToEvent(Event):
    def __init__(self, time, cpu):
        super(SwitchToEvent, self).__init__(time, cpu)
        self.layer = Canvas.BOTTOM_LAYER
        self.corresp_end_event = None
        
    def __str__(self):
        if self.corresp_end_event is None:
            return 'Switch To (w/o Switch Away)' + self._common_str() + ', TIME=' \
                   + str(self.get_time())
        return 'Scheduled' + self._common_str() + ', START=' \
               + util.format_float(self.get_time(), Event.NUM_DEC_PLACES) \
               + ', END=' + util.format_float(self.corresp_end_event.get_time(), Event.NUM_DEC_PLACES)
        
    def scan(self, cur_cpu, switches):
        old_cur_cpu = cur_cpu[0]
        cur_cpu[0] = self.get_cpu()
        switches[SwitchToEvent] = self
        self.corresp_end_event = None
        
        if old_cur_cpu != Event.NO_CPU:
            self.erroneous = True
            #print "currently scheduled somewhere, can't switch to a CPU"
                            
        super(SwitchToEvent, self).scan(cur_cpu, switches)
    
    def render(self, graph, layer, prev_events, selectable=False):
        if layer == self.layer:
            end_time = None
            clip = None
            if self.corresp_end_event is None:
                end_time = self.get_job().get_task().get_schedule().end
                clip = AlignMode.RIGHT
            else:
                end_time = self.corresp_end_event.get_time()
            
            prev_events[self] = None
            cpu = self.get_cpu()
            task_no = self.get_job().get_task().get_task_no()
            if selectable:
                graph.add_sel_bar_at_time(self.get_time(), end_time,
                                     task_no, cpu, self)
            else:
                graph.draw_bar_at_time(self.get_time(), end_time,
                                   task_no, cpu, self.get_job().get_job_no(),
                                   clip, self.is_selected())
                                           
class SwitchAwayEvent(Event):
    def __init__(self, time, cpu):
        super(SwitchAwayEvent, self).__init__(time, cpu)
        self.layer = Canvas.BOTTOM_LAYER
        self.corresp_start_event = None
    
    def __str__(self):
        if self.corresp_start_event is None:
            return 'Switch Away (w/o Switch To)' + self._common_str() + 'TIME=' \
                   + str(self.get_time())
        return str(self.corresp_start_event)
            
    def scan(self, cur_cpu, switches):
        old_cur_cpu = cur_cpu[0]
        
        self.corresp_start_event = switches[SwitchToEvent]
        
        cur_cpu[0] = Event.NO_CPU
        switches[SwitchToEvent] = None
        
        if self.corresp_start_event is not None:
            self.corresp_start_event.corresp_end_event = self
            
        if self.get_cpu() != old_cur_cpu:
            self.erroneous = True
            #print "switching away from a CPU different from the CPU we are currently on"
        if self.corresp_start_event is None:
            self.erroneous = True
            #print "switch away was not matched by a corresponding switch to"
        elif self.get_time() < self.corresp_start_event.get_time():
            self.erroneous = True
            #print "switching away from a processor before we switched to it?!"
        
        super(SwitchAwayEvent, self).scan(cur_cpu, switches)
            
    def render(self, graph, layer, prev_events, selectable=False):
        if self.corresp_start_event is None:
            # We never found a corresponding start event. In that case, we can assume it lies
            # in some part of the trace that was never read in. So draw a bar starting from
            # the very beginning.
            if layer == self.layer:
                prev_events[self] = None
                cpu = self.get_cpu()
                task_no = self.get_job().get_task().get_task_no()
                start = self.get_job().get_task().get_schedule().start
                if selectable:
                    graph.add_sel_bar_at_time(start, self.get_time(),
                                     task_no, cpu, self)
                else:
                    graph.draw_bar_at_time(start, self.get_time(),
                                   task_no, cpu, self.get_job().get_job_no(),
                                   AlignMode.LEFT, self.is_selected())
        else:
            if self.corresp_start_event in prev_events:
                return # already rendered the bar
            self.corresp_start_event.render(graph, layer, prev_events, selectable)
        
class ReleaseEvent(Event):
    def __init__(self, time, cpu):
        super(ReleaseEvent, self).__init__(time, cpu)
        self.layer = Canvas.TOP_LAYER
    
    def __str__(self):
        return 'Release' + self._common_str() + ', TIME=' + util.format_float(self.get_time(), Event.NUM_DEC_PLACES)
        
    def scan(self, cur_cpu, switches):
        super(ReleaseEvent, self).scan(cur_cpu, switches)
        
    def render(self, graph, layer, prev_events, selectable=False):
        prev_events[self] = None
        if layer == Canvas.TOP_LAYER:
            if selectable:
                graph.add_sel_release_arrow_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                            self)
            else:
                graph.draw_release_arrow_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                             self.get_job().get_job_no(), self.is_selected())
            
                                             
class DeadlineEvent(Event):
    def __init__(self, time, cpu):
        super(DeadlineEvent, self).__init__(time, cpu)
        self.layer = Canvas.TOP_LAYER
    
    def __str__(self):
        return 'Deadline' + self._common_str() + ', TIME=' + util.format_float(self.get_time(), Event.NUM_DEC_PLACES)
            
    def scan(self, cur_cpu, switches):
        super(DeadlineEvent, self).scan(cur_cpu, switches)
        
    def render(self, graph, layer, prev_events, selectable=False):
        prev_events[self] = None
        if layer == Canvas.TOP_LAYER:
            if selectable:
                graph.add_sel_deadline_arrow_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                              self)
            else:
                graph.draw_deadline_arrow_at_time(self.get_time(), self.get_job().get_task().get_task_no(),
                                              self.get_job().get_job_no(), self.is_selected())
            

class InversionStartEvent(ErrorEvent):
    def __init__(self, time):
        super(InversionStartEvent, self).__init__(time, Event.NO_CPU)
        self.layer = Canvas.BOTTOM_LAYER
        self.corresp_end_event = None
    
    def __str__(self):
        if self.corresp_end_event is None:
            return 'Inversion Start (w/o Inversion End)' + self._common_str() \
                  + ', TIME=' + util.format_float(self.get_time(), Event.NUM_DEC_PLACES)
        return 'Priority Inversion' + self._common_str() + ', START=' \
               + util.format_float(self.get_time(), Event.NUM_DEC_PLACES) \
               + ', END=' + util.format_float(self.corresp_end_event.get_time(), Event.NUM_DEC_PLACES)
        
    def scan(self, cur_cpu, switches):
        switches[InversionStartEvent] = self
        self.corresp_end_event = None
        
        # the corresp_end_event should already be set
        super(InversionStartEvent, self).scan(cur_cpu, switches)
    
    def render(self, graph, layer, prev_events, selectable=False):
        if layer == self.layer:
            end_time = None
            clip = None
            if self.corresp_end_event is None:
                end_time = self.get_job().get_task().get_schedule().end
                clip = AlignMode.RIGHT
            else:
                end_time = self.corresp_end_event.get_time()
            
            if layer == self.layer:
                prev_events[self] = None
                cpu = self.get_cpu()
                task_no = self.get_job().get_task().get_task_no()
                if selectable:
                    graph.add_sel_mini_bar_at_time(self.get_time(), end_time,
                                     task_no, cpu, self)
                else:
                    graph.draw_mini_bar_at_time(self.get_time(), end_time,
                                     task_no, cpu, self.get_job().get_job_no(),
                                     clip, self.is_selected())
            

class InversionEndEvent(ErrorEvent):
    def __init__(self, time):
        super(InversionEndEvent, self).__init__(time, Event.NO_CPU)
        self.layer = Canvas.BOTTOM_LAYER
        self.corresp_start_event = None
    
    def __str__(self):
        if self.corresp_start_event is None:
            return 'Inversion End (w/o Inversion Start)' + self._common_str() \
                  + ', TIME=' + util.format_float(self.get_time(), Event.NUM_DEC_PLACES)
        
        return str(self.corresp_start_event)
                      
    def scan(self, cur_cpu, switches):
        self.corresp_start_event = switches[InversionStartEvent]
        
        cur_cpu[0] = Event.NO_CPU
        switches[InversionStartEvent] = None
        
        if self.corresp_start_event is not None:
            self.corresp_start_event.corresp_end_event = self
            
        if self.corresp_start_event is None:
            self.erroneous = True
            print "inversion end was not matched by a corresponding inversion start"
        
        super(InversionEndEvent, self).scan(cur_cpu, switches)
        
    def render(self, graph, layer, prev_events, selectable=False):
        if self.corresp_start_event is None:
            # We never found a corresponding start event. In that case, we can assume it lies
            # in some part of the trace that was never read in. So draw a bar starting from
            # the very beginning.
            if layer == self.layer:
                prev_events[self] = None
                cpu = self.get_cpu()
                task_no = self.get_job().get_task().get_task_no()
                start = self.get_job().get_task().get_schedule().start
                if selectable:
                    graph.add_sel_mini_bar_at_time(start, self.get_time(),
                                     task_no, cpu, self)
                else:
                    graph.draw_mini_bar_at_time(start, self.get_time(),
                                   task_no, cpu, self.get_job().get_job_no(),
                                   AlignMode.LEFT, self.is_selected())
        else:
            if self.corresp_start_event in prev_events:
                return # already rendered the bar
            self.corresp_start_event.render(graph, layer, prev_events, selectable)
        
class InversionDummy(DummyEvent):
    def __init__(self, time, cpu):
        super(InversionDummy, self).__init__(time, Event.NO_CPU)
        self.layer = Canvas.BOTTOM_LAYER
        
    def render(self, graph, layer, prev_events, selectable=False):
        if self.corresp_start_event is None:
            if self.corresp_end_event in prev_events:
                return # we have already been rendered
            self.corresp_end_event.render(graph, layer, prev_events, selectable)
        else:    
            if self.corresp_start_event in prev_events:
                return # we have already been rendered
            self.corresp_start_event.render(graph, layer, prev_events, selectable)
        
class IsRunningDummy(DummyEvent):
    def __init__(self, time, cpu):
        super(IsRunningDummy, self).__init__(time, Event.NO_CPU)
        self.layer = Canvas.BOTTOM_LAYER
        
    def render(self, graph, layer, prev_events, selectable=False):
        if self.corresp_start_event is None:
            if self.corresp_end_event in prev_events:
                return # we have already been rendered
            self.corresp_end_event.render(graph, layer, prev_events, selectable)
        else:
            if self.corresp_start_event in prev_events:
                return # we have already been rendered
            self.corresp_start_event.render(graph, layer, prev_events, selectable)

EVENT_LIST = {SuspendEvent : None, ResumeEvent : None, CompleteEvent : None,
              SwitchAwayEvent : None, SwitchToEvent : None, ReleaseEvent : None,
              DeadlineEvent : None, IsRunningDummy : None,
              InversionStartEvent : None, InversionEndEvent : None,
              InversionDummy : None}

SPAN_START_EVENTS = { SwitchToEvent : IsRunningDummy, InversionStartEvent : InversionDummy }
SPAN_END_EVENTS = { SwitchAwayEvent : IsRunningDummy, InversionEndEvent : InversionDummy}