Source code for BSPy

from collections import deque
import multiprocessing as mp
from sys import version_info
import itertools
import time

[docs]class BSPObject: """The main BSP object that enables use of BSP This class keeps track of communication lines, its pid and the total cores it also enables the use of BSP functions through these variables. This is a low level object which the end user should not need to call directly. Parameters ---------- cores : int The total number of cores in this BSP instance. pid : int This processor's id. It always holds that 0 <= pid < cores. pipe_dict : dict of Pipeconnection A connection to every other processor. Should be given through the run() function. barrier : barrier The barrier object all processors adhere to. Attributes ---------- cores : int The total number of cores in this BSP instance (run). pid : int This processor's id. It always holds that 0 <= pid < cores""" def __init__(self, cores, pid, pipe_dict, barrier): # These should be static self._pipe_dict = pipe_dict self._barrier = barrier self.cores = cores self.pid = pid # These are expected to be dynamic and change. self._to_send_dict = {} self._queue = deque() def _clear_to_send(self): """Clears the _to_send dictionary. Should not be used by the end user in normal operation. Returns ------- out : None""" self._to_send_dict = {} def _is_empty(self, comm_line): """ Tells you if the comm_line is empty Parameters ---------- comm_line : Pipe or Queue The communication line you're asking about. Returns ------- out : bool True if comm_line is empty, False otherwise. """ if type(comm_line) == mp.connection.PipeConnection: empty = not comm_line.poll() elif type(comm_line) == mp.queues.Queue: empty = comm_line.empty() else: raise TypeError("comm_line is neither a queue, nor a pipe") return empty
[docs] def sync(self): """sync() Starts the synchronisation defined in the BSP model. A synchronisation consists of 3 distinct steps: 1) Wait for all processing nodes to finish computing 2) Send all messages that have queued up since the last sync 3) Receive all messages that have been sent in the previous step. After sync() has completed, every processor will have access to the data that has been sent to it. Returns ------- out : None""" # Ensure every processor is done doing what it was doing before self._barrier.wait() # Send all data for key in self._to_send_dict: # Pick the right communication line comm_line = self._pipe_dict[key] send_queue = self._to_send_dict[key] # Until the send_queue is empty while send_queue: # Pop the first message in send_queue, and send it. message = send_queue.popleft() if type(comm_line) == mp.connection.PipeConnection: # comm_line is a Pipe object comm_line.send(message) elif type(comm_line) == mp.queues.Queue: # comm_line is a Queue object, so use put comm_line.put(message) else: raise TypeError("comm_line is neither a queue, nor a pipe") # Clear _to_send_dict self._clear_to_send() # Ensure sending is done self._barrier.wait() # Clear the previous incoming _queue self._queue = deque() # Go through every pipe (to get data) for key in self._pipe_dict: comm_line = self._pipe_dict[key] while not self._is_empty(comm_line): if type(comm_line) == mp.connection.PipeConnection: # comm_line is a Pipe object message = comm_line.recv() elif type(comm_line) == mp.queues.Queue: # comm_line is a Queue object, so use get # Nothing can change in the size of the comm_line queue now; # we've already sent everything in the previous step. # Hence, we can reliably use the size of the queue to see if we can get. message = comm_line.get() else: raise TypeError("comm_line is neither a queue, nor a pipe") self._queue.append(message) # Ensure getting is done self._barrier.wait()
# Everyone is released and the _barrier reset.
[docs] def send(self, message, pid): """ Sends a message to the processor identified with pid. Parameters ---------- message : literally anything Whatever data you wish to transfer between processors pid : int The processor id to which you wish to send a message. Returns ------- out : None""" # Add message to _queue if pid not in self._to_send_dict: self._to_send_dict[pid] = deque() self._to_send_dict[pid].append(message)
[docs] def move(self): """ Acquires the first message stored in the receiving queue. Used to grab data from the receiving queue. This is a pop-like function and previously returned data cannot be returned a second time. returns None if queue is empty. Returns ------- out : queue data The first element in the processor's "receive" queue.""" if len(self._queue) > 0: message = self._queue.popleft() else: message = None return message
[docs] @staticmethod def time(): """Records the current Unix time in seconds of the system as a float. Returns ------- out : float Current Unix time in seconds""" if version_info >= (3, 7): return time.time_ns() / (10 ** 9) # Convert to floating-point seconds else: return time.time()
[docs] def nprocs(self): """Finds number of available processors in BSP instance. Returns ------- out : int Number of processors participating in the current BSP instance.""" return self.cores
def _create_pipes(cores): """Creates all communication pipes between processors. Sets up pipes and queues for all processors by using a dict of dicts. Part of this dict of dicts will be sent to every processor for communication when the run() function is called. Parameters ---------- cores : int The total number of cores you'll be running your BSP instance with. Returns ------- out : dict of dicts A dictionary that connects each processor together.""" # Create all combinations of channels channels = itertools.combinations(range(cores), 2) # This lists all graph edges. pipe_dict = {} # Add self references ((1,1), (2,2), etc) for core in range(cores): # Create a _queue self_queue = mp.Queue() pipe_dict[core] = {} pipe_dict[core][core] = self_queue for channel in channels: # Create the actual pipe end1, end2 = mp.Pipe() # Get processor numbers proc1, proc2 = channel # Every key already exists because we made self-relations. pipe_dict[proc1][proc2] = end1 pipe_dict[proc2][proc1] = end2 return pipe_dict
[docs]def run(function, cores=0, *args): """Execute function on number of cores specified. This is how a BSP program is launched. Function needs to be of the form func(BSP:BSPObject). run() needs to be nested in an if __name__ = '__main__' statement. Parameters ---------- function : callable A callable function to run in BSP. cores : int, optional The amount of cores you wish to use Defaults to all available cores *args : optional Any arguments you wish to pass on to your function. Returns ------- out : None""" try: # If cores isn't given or is 0, then set to maximum if not cores: cores = mp.cpu_count() # Core exception handling if type(cores) != int: raise TypeError("Cores must be an int") if cores < 0: raise ValueError("Cores must be positive") # Function exception handling if not callable(function): raise TypeError("Function must be callable") # First open all communication channels. # There will be be n(n-1)/2 channels. pipe_dict = _create_pipes(cores) # Then create a _barrier barrier = mp.Barrier(cores) # Start all processes one after the other. for i in range(cores): # Create a BSP data object bsp = BSPObject(cores=cores, pid=i, pipe_dict=pipe_dict[i], barrier=barrier) # Send BSP object p = mp.Process(target=function, args=(bsp, *args)) p.start() except RuntimeError: raise RuntimeError(''' An attempt has been made to start a new process before the current process has finished its bootstrapping phase. This probably means that you tried to use the run function but have forgotten to use the proper safeguard: if __name__ == '__main__': run(function, cores) This is essential for the program to run properly.''')
[docs]def max_cores(): """Finds number of available processors of the system. Returns ---------- out : int Maximum number of available processors.""" return mp.cpu_count()