Python CpuSnapshot.assignJob方法代码示例

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class HeadDoubleEasyScheduler(EasyBackfillScheduler):
    def __init__(self, num_processors):
        super(HeadDoubleEasyScheduler, self).__init__(num_processors)
        self.cpu_snapshot = CpuSnapshot(num_processors)

    def _schedule_head_of_list(self, current_time):
        "Overriding parent method"

        result = []
        while True:
            if len(self.unscheduled_jobs) == 0:
                break
            # check if the first job can be scheduled at current time
            if (
                self.cpu_snapshot.free_processors_available_at(current_time)
                >= self.unscheduled_jobs[0].num_required_processors
            ):
                job = self.unscheduled_jobs.pop(0)
                job.predicted_run_time = 2 * job.user_estimated_run_time  # doubling is done here
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                # first job can't be scheduled
                break
        return result

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class  TailDoubleEasyScheduler(EasyBackfillScheduler):
    """ This algorithm implements the algorithm in the paper of Tsafrir, Etzion, Feitelson, june 2007?
    """
    
    def __init__(self, options):
        super(TailDoubleEasyScheduler, self).__init__(options)
        self.cpu_snapshot = CpuSnapshot(self.num_processors, options["stats"])

    
    def _backfill_jobs(self, current_time):
        "Overriding parent method"
        if len(self.unscheduled_jobs) <= 1:
            return []

        result = []  
        first_job = self.unscheduled_jobs[0]        
        tail =  list_copy(self.unscheduled_jobs[1:]) 
        
        self.cpu_snapshot.assignJobEarliest(first_job, current_time)
        
        for job in tail:
            job.predicted_run_time = 2 * job.user_estimated_run_time # doubling is done here 
            if self.cpu_snapshot.canJobStartNow(job, current_time): # if job can be backfilled 
                self.unscheduled_jobs.remove(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                job.predicted_run_time = job.user_estimated_run_time # undoubling is done here 
                
        self.cpu_snapshot.delJobFromCpuSlices(first_job)

        return result

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class  ReverseEasyScheduler(EasyBackfillScheduler):
    
    def __init__(self, options):
        super(ReverseEasyScheduler, self).__init__(options)
        self.cpu_snapshot = CpuSnapshot(self.num_processors, options["stats"])

    
    def _backfill_jobs(self, current_time):
        "Overriding parent method"
        if len(self.unscheduled_jobs) <= 1:
            return []

        result = []  
        first_job = self.unscheduled_jobs[0]        
        tail =  list_copy(self.unscheduled_jobs[1:])
        tail_of_jobs_by_reverse_order = sorted(tail, key=latest_sort_key)
        
        self.cpu_snapshot.assignJobEarliest(first_job, current_time)
        
        for job in tail_of_jobs_by_reverse_order:
            if self.cpu_snapshot.canJobStartNow(job, current_time): 
                self.unscheduled_jobs.remove(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
                
        self.cpu_snapshot.delJobFromCpuSlices(first_job)

        return result

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class FcfsScheduler(Scheduler):

    def __init__(self, options):
        super(FcfsScheduler, self).__init__(options)
        self.cpu_snapshot = CpuSnapshot(self.num_processors, options["stats"])
        self.waiting_queue_of_jobs = []

    def new_events_on_job_submission(self, job, current_time):
        self.cpu_snapshot.archive_old_slices(current_time)
        self.waiting_queue_of_jobs.append(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]

    def new_events_on_job_termination(self, job, current_time):
        self.cpu_snapshot.archive_old_slices(current_time)
        self.cpu_snapshot.delTailofJobFromCpuSlices(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]


    def _schedule_jobs(self, current_time):
        result = []
        while len(self.waiting_queue_of_jobs) > 0:
            job = self.waiting_queue_of_jobs[0]
            if self.cpu_snapshot.free_processors_available_at(current_time) >= job.num_required_processors:
                self.waiting_queue_of_jobs.pop(0)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                break
        return result

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class EasySJBFScheduler(EasyBackfillScheduler):
    """ This algorithm implements the algorithm in the paper of Tsafrir, Etzion, Feitelson, june 2007?
    """

    def __init__(self, num_processors):
        super(EasySJBFScheduler, self).__init__(num_processors)
        self.cpu_snapshot = CpuSnapshot(num_processors)

    def _backfill_jobs(self, current_time):
        "Overriding parent method"
        if len(self.unscheduled_jobs) <= 1:
            return []

        result = []
        first_job = self.unscheduled_jobs[0]
        tail = list_copy(self.unscheduled_jobs[1:])
        tail_of_jobs_by_sjf_order = sorted(tail, key=sjf_sort_key)

        self.cpu_snapshot.assignJobEarliest(first_job, current_time)

        for job in tail_of_jobs_by_sjf_order:
            if self.cpu_snapshot.canJobStartNow(job, current_time):
                self.unscheduled_jobs.remove(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)

        self.cpu_snapshot.delJobFromCpuSlices(first_job)

        return result

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class LogScheduler(Scheduler):

    def __init__(self, num_processors):
        super(LogScheduler, self).__init__(num_processors)
        self.cpu_snapshot = CpuSnapshot(num_processors)
        self.waiting_queue_of_jobs = []

    def new_events_on_job_submission(self, job, current_time):
        self.cpu_snapshot.archive_old_slices(current_time)
	result = []        
	#self.waiting_queue_of_jobs.append(job)
	result.append(JobStartEvent(current_time+job.actual_wait_time, job))
        #return [
        #    JobStartEvent(current_time, job)
        #    for job in self._log_schedule_jobs(current_time)
        #]
	return result

    def new_events_on_job_termination(self, job, current_time):
        self.cpu_snapshot.archive_old_slices(current_time)
        self.cpu_snapshot.delTailofJobFromCpuSlices(job)
	return []        
	"""return [
            JobStartEvent(current_time, job)
            for job in self._log_schedule_jobs(current_time)
        ]"""


    def _schedule_jobs(self, current_time):
        result = []
        while len(self.waiting_queue_of_jobs) > 0:
            job = self.waiting_queue_of_jobs[0]
            if self.cpu_snapshot.free_processors_available_at(current_time) >= job.num_required_processors:
                self.waiting_queue_of_jobs.pop(0)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                break
        return result
    
    def _log_schedule_jobs(self, current_time):                 #by Siddharth
        result = []
	return result
        """while len(self.waiting_queue_of_jobs) > 0:

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class EasyBackfillScheduler(Scheduler):

    def __init__(self, options):
        super(EasyBackfillScheduler, self).__init__(options)
        self.cpu_snapshot = CpuSnapshot(self.num_processors, options["stats"])
        self.unscheduled_jobs = []

    def new_events_on_job_submission(self, just_submitted_job, current_time):
        """ Here we first add the new job to the waiting list. We then try to schedule
        the jobs in the waiting list, returning a collection of new termination events """
        # TODO: a probable performance bottleneck because we reschedule all the
        # jobs. Knowing that only one new job is added allows more efficient
        # scheduling here.
        self.cpu_snapshot.archive_old_slices(current_time)
        self.unscheduled_jobs.append(just_submitted_job)
        
        retl = []
        
        if (self.cpu_snapshot.free_processors_available_at(current_time) >= just_submitted_job.num_required_processors):
		for job in self._schedule_jobs(current_time):
			retl.append(JobStartEvent(current_time, job))
        
        return retl

    def new_events_on_job_termination(self, job, current_time):
        """ Here we first delete the tail of the just terminated job (in case it's
        done before user estimation time). We then try to schedule the jobs in the waiting list,
        returning a collection of new termination events """
        self.cpu_snapshot.archive_old_slices(current_time)
        self.cpu_snapshot.delTailofJobFromCpuSlices(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]

    def _schedule_jobs(self, current_time):
        "Schedules jobs that can run right now, and returns them"
        jobs = self._schedule_head_of_list(current_time)
        jobs += self._backfill_jobs(current_time)
        return jobs

    def _schedule_head_of_list(self, current_time):     
        result = []
        while True:
            if len(self.unscheduled_jobs) == 0:
                break
            # Try to schedule the first job
            if self.cpu_snapshot.free_processors_available_at(current_time) >= self.unscheduled_jobs[0].num_required_processors:
                job = self.unscheduled_jobs.pop(0)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                # first job can't be scheduled
                break
        return result

    def _backfill_jobs(self, current_time):
        """
        Find jobs that can be backfilled and update the cpu snapshot.
        DEPRECATED FUNCTION !!!!!!
        """
        if len(self.unscheduled_jobs) <= 1:
            return []
        
        result = []


        tail_of_waiting_list = list_copy(self.unscheduled_jobs[1:])
        
        first_job = self.unscheduled_jobs[0]
        self.cpu_snapshot.assignJobEarliest(first_job, current_time)
        
        for job in tail_of_waiting_list:
            if self.cpu_snapshot.canJobStartNow(job, current_time):
                job.is_backfilled = 1
                self.unscheduled_jobs.remove(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
        self.cpu_snapshot.unAssignJob(first_job)

        return result

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class  EasyPlusPlusScheduler(Scheduler):
    """ This algorithm implements the algorithm in the paper of Tsafrir, Etzion, Feitelson, june 2007?
    """

    I_NEED_A_PREDICTOR = True

    def __init__(self, options):
        super(EasyPlusPlusScheduler, self).__init__(options)
        self.init_predictor(options)
        self.init_corrector(options)

        self.cpu_snapshot = CpuSnapshot(self.num_processors, options["stats"])
        self.unscheduled_jobs = []


    def new_events_on_job_submission(self, job, current_time):

        self.cpu_snapshot.archive_old_slices(current_time)
        self.predictor.predict(job, current_time, self.running_jobs)
        if not hasattr(job,"initial_prediction"):
            job.initial_prediction=job.predicted_run_time
        self.unscheduled_jobs.append(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]


    def new_events_on_job_termination(self, job, current_time):
        self.predictor.fit(job, current_time)

        if self.corrector.__name__=="ninetynine":
            self.pestimator.fit(job.actual_run_time/job.user_estimated_run_time)

        self.cpu_snapshot.archive_old_slices(current_time)
        self.cpu_snapshot.delTailofJobFromCpuSlices(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]


    def new_events_on_job_under_prediction(self, job, current_time):
        pass #assert job.predicted_run_time <= job.user_estimated_run_time

        if not hasattr(job,"num_underpredict"):
            job.num_underpredict = 0
        else:
            job.num_underpredict += 1

        if self.corrector.__name__=="ninetynine":
            new_predicted_run_time = self.corrector(self.pestimator,job,current_time)
        else:
            new_predicted_run_time = self.corrector(job, current_time)

        #set the new predicted runtime
        self.cpu_snapshot.assignTailofJobToTheCpuSlices(job, new_predicted_run_time)
        job.predicted_run_time = new_predicted_run_time

        return [JobStartEvent(current_time, job)]


    def _schedule_jobs(self, current_time):
        "Schedules jobs that can run right now, and returns them"

        jobs  = self._schedule_head_of_list(current_time)
        jobs += self._backfill_jobs(current_time)
        return jobs


    def _schedule_head_of_list(self, current_time):
        result = []
        while True:
            if len(self.unscheduled_jobs) == 0:
                break
            # Try to schedule the first job
            if self.cpu_snapshot.free_processors_available_at(current_time) >= self.unscheduled_jobs[0].num_required_processors:
                job = self.unscheduled_jobs.pop(0)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                # first job can't be scheduled
                break
        return result


    def _backfill_jobs(self, current_time):
        if len(self.unscheduled_jobs) <= 1:
            return []

        result = []
        first_job = self.unscheduled_jobs[0]
        tail =  list_copy(self.unscheduled_jobs[1:])
        tail_of_jobs_by_sjf_order = sorted(tail, key=sjf_sort_key)

        self.cpu_snapshot.assignJobEarliest(first_job, current_time)

        for job in tail_of_jobs_by_sjf_order:
            if self.cpu_snapshot.canJobStartNow(job, current_time):
                job.is_backfilled = 1
#.........这里部分代码省略.........

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class  OrigProbabilisticEasyScheduler(Scheduler):
    """ This algorithm implements a version of Feitelson and Nissimov, June 2007 
    """
    
    def __init__(self, num_processors, threshold = 0.2, window_size=150):
        super(OrigProbabilisticEasyScheduler, self).__init__(num_processors)
        self.threshold    = threshold
        self.window_size  = window_size # a parameter for the distribution 
        self.cpu_snapshot = CpuSnapshot(num_processors)
        
        self.user_distribution = {}

        self.unscheduled_jobs  = []
        self.currently_running_jobs = []
     
        #self.work_list = [[None for i in xrange(self.num_processors+1)] for j in xrange(self.num_processors+1)]
        self.M = {}        
        for c in xrange(self.num_processors+1):
            for n in xrange(self.num_processors+1):
                self.M[c, n] = 0.0

        self.max_user_rounded_estimated_run_time = 0
        self.prev_max_user_rounded_estimated_run_time = 0

        

    def new_events_on_job_submission(self, job, current_time):
        # print "arrived:", job
        rounded_up_estimated_time = _round_time_up(job.user_estimated_run_time)

        if  rounded_up_estimated_time > self.max_user_rounded_estimated_run_time:
            self.prev_max_user_rounded_estimated_run_time = self.max_user_rounded_estimated_run_time
            self.max_user_rounded_estimated_run_time = rounded_up_estimated_time
    
        if  not self.user_distribution.has_key(job.user_id):
            self.user_distribution[job.user_id] = Distribution(job, self.window_size)
        self.user_distribution[job.user_id].touch(2*self.max_user_rounded_estimated_run_time)

        if  self.prev_max_user_rounded_estimated_run_time < self.max_user_rounded_estimated_run_time:
            for tmp_job in self.currently_running_jobs:
                self.user_distribution[tmp_job.user_id].touch(2*self.max_user_rounded_estimated_run_time)
              
        self.cpu_snapshot.archive_old_slices(current_time)
        self.unscheduled_jobs.append(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]


    def new_events_on_job_termination(self, job, current_time):
        self.user_distribution[job.user_id].add_job(job)
        self.currently_running_jobs.remove(job)
        self.cpu_snapshot.archive_old_slices(current_time)
        self.cpu_snapshot.delTailofJobFromCpuSlices(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]


    def _schedule_jobs(self, current_time):
        "Schedules jobs that can run right now, and returns them"
        jobs  = self._schedule_head_of_list(current_time)
        jobs += self._backfill_jobs(current_time)
        return jobs


    def _schedule_head_of_list(self, current_time):     
        result = []
        while True:
            if len(self.unscheduled_jobs) == 0:
                break
            # Try to schedule the first job
            if self.cpu_snapshot.free_processors_available_at(current_time) >= self.unscheduled_jobs[0].num_required_processors:
                job = self.unscheduled_jobs.pop(0)
                self.currently_running_jobs.append(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                # first job can't be scheduled
                break
        return result
    

    def _backfill_jobs(self, current_time):
        if len(self.unscheduled_jobs) <= 1:
            return []

        result    = []  
        first_job = self.unscheduled_jobs[0]        
        tail      = list_copy(self.unscheduled_jobs[1:]) 
                
        for job in tail:
            if self.can_be_probabilistically_backfilled(job, current_time):
                self.unscheduled_jobs.remove(job)
                self.currently_running_jobs.append(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)                
        return result
#.........这里部分代码省略.........

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class  EasyPlusPlusScheduler(Scheduler):
    """ This algorithm implements the algorithm in the paper of Tsafrir, Etzion, Feitelson, june 2007?
    """
    
    def __init__(self, num_processors):
        super(EasyPlusPlusScheduler, self).__init__(num_processors)
        self.cpu_snapshot = CpuSnapshot(num_processors)
        self.unscheduled_jobs = []
        self.user_run_time_prev = {}
        self.user_run_time_last = {}

    
    def new_events_on_job_submission(self, job, current_time):
        if not self.user_run_time_last.has_key(job.user_id): 
            self.user_run_time_prev[job.user_id] = None 
            self.user_run_time_last[job.user_id] = None

        self.cpu_snapshot.archive_old_slices(current_time)
        self.unscheduled_jobs.append(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]


    def new_events_on_job_termination(self, job, current_time):
        assert self.user_run_time_last.has_key(job.user_id) == True
        assert self.user_run_time_prev.has_key(job.user_id) == True

        self.user_run_time_prev[job.user_id] = self.user_run_time_last[job.user_id]
        self.user_run_time_last[job.user_id] = job.actual_run_time
        self.cpu_snapshot.archive_old_slices(current_time)
        self.cpu_snapshot.delTailofJobFromCpuSlices(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]


    def new_events_on_job_under_prediction(self, job, current_time):
        assert job.predicted_run_time <= job.user_estimated_run_time

        self.cpu_snapshot.assignTailofJobToTheCpuSlices(job)
        job.predicted_run_time = job.user_estimated_run_time
        return []


    def _schedule_jobs(self, current_time):
        "Schedules jobs that can run right now, and returns them"
   
        for job in self.unscheduled_jobs:
            if self.user_run_time_prev[job.user_id] != None: 
                average =  int((self.user_run_time_last[job.user_id] + self.user_run_time_prev[job.user_id])/ 2)
                job.predicted_run_time = min (job.user_estimated_run_time, average)

        jobs  = self._schedule_head_of_list(current_time)
        jobs += self._backfill_jobs(current_time)
        return jobs


    def _schedule_head_of_list(self, current_time):     
        result = []
        while True:
            if len(self.unscheduled_jobs) == 0:
                break
            # Try to schedule the first job
            if self.cpu_snapshot.free_processors_available_at(current_time) >= self.unscheduled_jobs[0].num_required_processors:
                job = self.unscheduled_jobs.pop(0)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                # first job can't be scheduled
                break
        return result
    

    def _backfill_jobs(self, current_time):
        if len(self.unscheduled_jobs) <= 1:
            return []

        result = []  
        first_job = self.unscheduled_jobs[0]        
        tail =  list_copy(self.unscheduled_jobs[1:])
        tail_of_jobs_by_sjf_order = sorted(tail, key=sjf_sort_key)
        
        self.cpu_snapshot.assignJobEarliest(first_job, current_time)
        
        for job in tail_of_jobs_by_sjf_order:
            if self.cpu_snapshot.canJobStartNow(job, current_time): 
                self.unscheduled_jobs.remove(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
                
        self.cpu_snapshot.delJobFromCpuSlices(first_job)

        return result

# 需要导入模块: from common import CpuSnapshot [as 别名]
# 或者: from common.CpuSnapshot import assignJob [as 别名]
class EasyBackfillScheduler(Scheduler):

    def __init__(self, num_processors):
        super(EasyBackfillScheduler, self).__init__(num_processors)
        self.cpu_snapshot = CpuSnapshot(num_processors)
        self.unscheduled_jobs = []
        
    def new_events_on_job_submission(self, just_submitted_job, current_time):
        """ Here we first add the new job to the waiting list. We then try to schedule
        the jobs in the waiting list, returning a collection of new termination events """
        # TODO: a probable performance bottleneck because we reschedule all the
        # jobs. Knowing that only one new job is added allows more efficient
        # scheduling here.
        #print 'User submits', just_submitted_job
        self.cpu_snapshot.archive_old_slices(current_time)
        self.unscheduled_jobs.append(just_submitted_job)
        #print 'At time', current_time, 'unscheduled:', self.unscheduled_jobs
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]

    def new_events_on_job_termination(self, job, current_time):
        """ Here we first delete the tail of the just terminated job (in case it's
        done before user estimation time). We then try to schedule the jobs in the waiting list,
        returning a collection of new termination events """
        self.cpu_snapshot.archive_old_slices(current_time)
        self.cpu_snapshot.delTailofJobFromCpuSlices(job)
        return [
            JobStartEvent(current_time, job)
            for job in self._schedule_jobs(current_time)
        ]

    def _schedule_jobs(self, current_time):
        "Schedules jobs that can run right now, and returns them"
        jobs  = self._schedule_head_of_list(current_time)
        jobs += self._backfill_jobs(current_time)
        #print 'Currently schedulable jobs:', jobs
        #print 'Currently schedulable jobs count:', len(jobs)
        self.totalScheduledJobs += len(jobs)
        return jobs

    def _schedule_head_of_list(self, current_time):     
        result = []
        while True:
            if len(self.unscheduled_jobs) == 0:
                break
            # Try to schedule the first job
            if self.cpu_snapshot.free_processors_available_at(current_time) >= self.unscheduled_jobs[0].num_required_processors:
                job = self.unscheduled_jobs.pop(0)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)
            else:
                # first job can't be scheduled
                break
        return result

    def _backfill_jobs(self, current_time):
        """
        Find jobs that can be backfilled and update the cpu snapshot.
        """
        if len(self.unscheduled_jobs) <= 1:
            return []
        
        result = []


        tail_of_waiting_list = list_copy(self.unscheduled_jobs[1:])
        
        for job in tail_of_waiting_list:
            if self.canBeBackfilled(job, current_time):
                self.unscheduled_jobs.remove(job)
                self.cpu_snapshot.assignJob(job, current_time)
                result.append(job)

        return result 

    def canBeBackfilled(self, second_job, current_time):
        assert len(self.unscheduled_jobs) >= 2
        assert second_job in self.unscheduled_jobs[1:]

        if self.cpu_snapshot.free_processors_available_at(current_time) < second_job.num_required_processors:
            return False

        first_job = self.unscheduled_jobs[0]

        temp_cpu_snapshot = self.cpu_snapshot.copy()
        temp_cpu_snapshot.assignJobEarliest(first_job, current_time)

        # if true, this means that the 2nd job is "independent" of the 1st, and thus can be backfilled
        return temp_cpu_snapshot.canJobStartNow(second_job, current_time)