add len(view)

corresponds to the number of associated engines

IPython/parallel/client/view.py

@@ -1,1093 +1,1100 b''
 """Views of remote engines.
 
 Authors:
 
 * Min RK
 """
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2010-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import imp
 import sys
 import warnings
 from contextlib import contextmanager
 from types import ModuleType
 
 import zmq
 
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils.traitlets import (
     HasTraits, Any, Bool, List, Dict, Set, Instance, CFloat, Integer
 )
 from IPython.external.decorator import decorator
 
 from IPython.parallel import util
 from IPython.parallel.controller.dependency import Dependency, dependent
 
 from . import map as Map
 from .asyncresult import AsyncResult, AsyncMapResult
 from .remotefunction import ParallelFunction, parallel, remote, getname
 
 #-----------------------------------------------------------------------------
 # Decorators
 #-----------------------------------------------------------------------------
 
 @decorator
 def save_ids(f, self, *args, **kwargs):
     """Keep our history and outstanding attributes up to date after a method call."""
     n_previous = len(self.client.history)
     try:
         ret = f(self, *args, **kwargs)
     finally:
         nmsgs = len(self.client.history) - n_previous
         msg_ids = self.client.history[-nmsgs:]
         self.history.extend(msg_ids)
         map(self.outstanding.add, msg_ids)
     return ret
 
 @decorator
 def sync_results(f, self, *args, **kwargs):
     """sync relevant results from self.client to our results attribute."""
     ret = f(self, *args, **kwargs)
     delta = self.outstanding.difference(self.client.outstanding)
     completed = self.outstanding.intersection(delta)
     self.outstanding = self.outstanding.difference(completed)
     for msg_id in completed:
         self.results[msg_id] = self.client.results[msg_id]
     return ret
 
 @decorator
 def spin_after(f, self, *args, **kwargs):
     """call spin after the method."""
     ret = f(self, *args, **kwargs)
     self.spin()
     return ret
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 @skip_doctest
 class View(HasTraits):
     """Base View class for more convenint apply(f,*args,**kwargs) syntax via attributes.
 
     Don't use this class, use subclasses.
 
     Methods
     -------
 
     spin
         flushes incoming results and registration state changes
         control methods spin, and requesting `ids` also ensures up to date
 
     wait
         wait on one or more msg_ids
 
     execution methods
         apply
         legacy: execute, run
 
     data movement
         push, pull, scatter, gather
 
     query methods
         get_result, queue_status, purge_results, result_status
 
     control methods
         abort, shutdown
 
     """
     # flags
     block=Bool(False)
     track=Bool(True)
     targets = Any()
 
     history=List()
     outstanding = Set()
     results = Dict()
     client = Instance('IPython.parallel.Client')
 
     _socket = Instance('zmq.Socket')
     _flag_names = List(['targets', 'block', 'track'])
     _targets = Any()
     _idents = Any()
 
     def __init__(self, client=None, socket=None, **flags):
         super(View, self).__init__(client=client, _socket=socket)
         self.block = client.block
 
         self.set_flags(**flags)
 
         assert not self.__class__ is View, "Don't use base View objects, use subclasses"
 
-
     def __repr__(self):
         strtargets = str(self.targets)
         if len(strtargets) > 16:
             strtargets = strtargets[:12]+'...]'
         return "<%s %s>"%(self.__class__.__name__, strtargets)
-
+    
+    def __len__(self):
+        if isinstance(self.targets, list):
+            return len(self.targets)
+        elif isinstance(self.targets, int):
+            return 1
+        else:
+            return len(self.client)
+    
     def set_flags(self, **kwargs):
         """set my attribute flags by keyword.
 
         Views determine behavior with a few attributes (`block`, `track`, etc.).
         These attributes can be set all at once by name with this method.
 
         Parameters
         ----------
 
         block : bool
             whether to wait for results
         track : bool
             whether to create a MessageTracker to allow the user to
             safely edit after arrays and buffers during non-copying
             sends.
         """
         for name, value in kwargs.iteritems():
             if name not in self._flag_names:
                 raise KeyError("Invalid name: %r"%name)
             else:
                 setattr(self, name, value)
 
     @contextmanager
     def temp_flags(self, **kwargs):
         """temporarily set flags, for use in `with` statements.
 
         See set_flags for permanent setting of flags
 
         Examples
         --------
 
         >>> view.track=False
         ...
         >>> with view.temp_flags(track=True):
         ...    ar = view.apply(dostuff, my_big_array)
         ...    ar.tracker.wait() # wait for send to finish
         >>> view.track
         False
 
         """
         # preflight: save flags, and set temporaries
         saved_flags = {}
         for f in self._flag_names:
             saved_flags[f] = getattr(self, f)
         self.set_flags(**kwargs)
         # yield to the with-statement block
         try:
             yield
         finally:
             # postflight: restore saved flags
             self.set_flags(**saved_flags)
 
 
     #----------------------------------------------------------------
     # apply
     #----------------------------------------------------------------
 
     @sync_results
     @save_ids
     def _really_apply(self, f, args, kwargs, block=None, **options):
         """wrapper for client.send_apply_request"""
         raise NotImplementedError("Implement in subclasses")
 
     def apply(self, f, *args, **kwargs):
         """calls f(*args, **kwargs) on remote engines, returning the result.
 
         This method sets all apply flags via this View's attributes.
 
         if self.block is False:
             returns AsyncResult
         else:
             returns actual result of f(*args, **kwargs)
         """
         return self._really_apply(f, args, kwargs)
 
     def apply_async(self, f, *args, **kwargs):
         """calls f(*args, **kwargs) on remote engines in a nonblocking manner.
 
         returns AsyncResult
         """
         return self._really_apply(f, args, kwargs, block=False)
 
     @spin_after
     def apply_sync(self, f, *args, **kwargs):
         """calls f(*args, **kwargs) on remote engines in a blocking manner,
          returning the result.
 
         returns: actual result of f(*args, **kwargs)
         """
         return self._really_apply(f, args, kwargs, block=True)
 
     #----------------------------------------------------------------
     # wrappers for client and control methods
     #----------------------------------------------------------------
     @sync_results
     def spin(self):
         """spin the client, and sync"""
         self.client.spin()
 
     @sync_results
     def wait(self, jobs=None, timeout=-1):
         """waits on one or more `jobs`, for up to `timeout` seconds.
 
         Parameters
         ----------
 
         jobs : int, str, or list of ints and/or strs, or one or more AsyncResult objects
                 ints are indices to self.history
                 strs are msg_ids
                 default: wait on all outstanding messages
         timeout : float
                 a time in seconds, after which to give up.
                 default is -1, which means no timeout
 
         Returns
         -------
 
         True : when all msg_ids are done
         False : timeout reached, some msg_ids still outstanding
         """
         if jobs is None:
             jobs = self.history
         return self.client.wait(jobs, timeout)
 
     def abort(self, jobs=None, targets=None, block=None):
         """Abort jobs on my engines.
 
         Parameters
         ----------
 
         jobs : None, str, list of strs, optional
             if None: abort all jobs.
             else: abort specific msg_id(s).
         """
         block = block if block is not None else self.block
         targets = targets if targets is not None else self.targets
         jobs = jobs if jobs is not None else list(self.outstanding)
         
         return self.client.abort(jobs=jobs, targets=targets, block=block)
 
     def queue_status(self, targets=None, verbose=False):
         """Fetch the Queue status of my engines"""
         targets = targets if targets is not None else self.targets
         return self.client.queue_status(targets=targets, verbose=verbose)
 
     def purge_results(self, jobs=[], targets=[]):
         """Instruct the controller to forget specific results."""
         if targets is None or targets == 'all':
             targets = self.targets
         return self.client.purge_results(jobs=jobs, targets=targets)
 
     def shutdown(self, targets=None, restart=False, hub=False, block=None):
         """Terminates one or more engine processes, optionally including the hub.
         """
         block = self.block if block is None else block
         if targets is None or targets == 'all':
             targets = self.targets
         return self.client.shutdown(targets=targets, restart=restart, hub=hub, block=block)
 
     @spin_after
     def get_result(self, indices_or_msg_ids=None):
         """return one or more results, specified by history index or msg_id.
 
         See client.get_result for details.
 
         """
 
         if indices_or_msg_ids is None:
             indices_or_msg_ids = -1
         if isinstance(indices_or_msg_ids, int):
             indices_or_msg_ids = self.history[indices_or_msg_ids]
         elif isinstance(indices_or_msg_ids, (list,tuple,set)):
             indices_or_msg_ids = list(indices_or_msg_ids)
             for i,index in enumerate(indices_or_msg_ids):
                 if isinstance(index, int):
                     indices_or_msg_ids[i] = self.history[index]
         return self.client.get_result(indices_or_msg_ids)
 
     #-------------------------------------------------------------------
     # Map
     #-------------------------------------------------------------------
 
     def map(self, f, *sequences, **kwargs):
         """override in subclasses"""
         raise NotImplementedError
 
     def map_async(self, f, *sequences, **kwargs):
         """Parallel version of builtin `map`, using this view's engines.
 
         This is equivalent to map(...block=False)
 
         See `self.map` for details.
         """
         if 'block' in kwargs:
             raise TypeError("map_async doesn't take a `block` keyword argument.")
         kwargs['block'] = False
         return self.map(f,*sequences,**kwargs)
 
     def map_sync(self, f, *sequences, **kwargs):
         """Parallel version of builtin `map`, using this view's engines.
 
         This is equivalent to map(...block=True)
 
         See `self.map` for details.
         """
         if 'block' in kwargs:
             raise TypeError("map_sync doesn't take a `block` keyword argument.")
         kwargs['block'] = True
         return self.map(f,*sequences,**kwargs)
 
     def imap(self, f, *sequences, **kwargs):
         """Parallel version of `itertools.imap`.
 
         See `self.map` for details.
 
         """
 
         return iter(self.map_async(f,*sequences, **kwargs))
 
     #-------------------------------------------------------------------
     # Decorators
     #-------------------------------------------------------------------
 
     def remote(self, block=True, **flags):
         """Decorator for making a RemoteFunction"""
         block = self.block if block is None else block
         return remote(self, block=block, **flags)
 
     def parallel(self, dist='b', block=None, **flags):
         """Decorator for making a ParallelFunction"""
         block = self.block if block is None else block
         return parallel(self, dist=dist, block=block, **flags)
 
 @skip_doctest
 class DirectView(View):
     """Direct Multiplexer View of one or more engines.
 
     These are created via indexed access to a client:
 
     >>> dv_1 = client[1]
     >>> dv_all = client[:]
     >>> dv_even = client[::2]
     >>> dv_some = client[1:3]
 
     This object provides dictionary access to engine namespaces:
 
     # push a=5:
     >>> dv['a'] = 5
     # pull 'foo':
     >>> db['foo']
 
     """
 
     def __init__(self, client=None, socket=None, targets=None):
         super(DirectView, self).__init__(client=client, socket=socket, targets=targets)
 
     @property
     def importer(self):
         """sync_imports(local=True) as a property.
 
         See sync_imports for details.
 
         """
         return self.sync_imports(True)
 
     @contextmanager
     def sync_imports(self, local=True, quiet=False):
         """Context Manager for performing simultaneous local and remote imports.
 
         'import x as y' will *not* work.  The 'as y' part will simply be ignored.
         
         If `local=True`, then the package will also be imported locally.
         
         If `quiet=True`, no output will be produced when attempting remote 
         imports. 
         
         Note that remote-only (`local=False`) imports have not been implemented.
         
         >>> with view.sync_imports():
         ...    from numpy import recarray
         importing recarray from numpy on engine(s)
 
         """
         import __builtin__
         local_import = __builtin__.__import__
         modules = set()
         results = []
         @util.interactive
         def remote_import(name, fromlist, level):
             """the function to be passed to apply, that actually performs the import
             on the engine, and loads up the user namespace.
             """
             import sys
             user_ns = globals()
             mod = __import__(name, fromlist=fromlist, level=level)
             if fromlist:
                 for key in fromlist:
                     user_ns[key] = getattr(mod, key)
             else:
                 user_ns[name] = sys.modules[name]
 
         def view_import(name, globals={}, locals={}, fromlist=[], level=-1):
             """the drop-in replacement for __import__, that optionally imports
             locally as well.
             """
             # don't override nested imports
             save_import = __builtin__.__import__
             __builtin__.__import__ = local_import
 
             if imp.lock_held():
                 # this is a side-effect import, don't do it remotely, or even
                 # ignore the local effects
                 return local_import(name, globals, locals, fromlist, level)
 
             imp.acquire_lock()
             if local:
                 mod = local_import(name, globals, locals, fromlist, level)
             else:
                 raise NotImplementedError("remote-only imports not yet implemented")
             imp.release_lock()
 
             key = name+':'+','.join(fromlist or [])
             if level == -1 and key not in modules:
                 modules.add(key)
                 if not quiet:
                     if fromlist:
                         print "importing %s from %s on engine(s)"%(','.join(fromlist), name)
                     else:
                         print "importing %s on engine(s)"%name
                 results.append(self.apply_async(remote_import, name, fromlist, level))
             # restore override
             __builtin__.__import__ = save_import
 
             return mod
 
         # override __import__
         __builtin__.__import__ = view_import
         try:
             # enter the block
             yield
         except ImportError:
             if local:
                 raise
             else:
                 # ignore import errors if not doing local imports
                 pass
         finally:
             # always restore __import__
             __builtin__.__import__ = local_import
 
         for r in results:
             # raise possible remote ImportErrors here
             r.get()
 
 
     @sync_results
     @save_ids
     def _really_apply(self, f, args=None, kwargs=None, targets=None, block=None, track=None):
         """calls f(*args, **kwargs) on remote engines, returning the result.
 
         This method sets all of `apply`'s flags via this View's attributes.
 
         Parameters
         ----------
 
         f : callable
 
         args : list [default: empty]
 
         kwargs : dict [default: empty]
 
         targets : target list [default: self.targets]
             where to run
         block : bool [default: self.block]
             whether to block
         track : bool [default: self.track]
             whether to ask zmq to track the message, for safe non-copying sends
 
         Returns
         -------
 
         if self.block is False:
             returns AsyncResult
         else:
             returns actual result of f(*args, **kwargs) on the engine(s)
             This will be a list of self.targets is also a list (even length 1), or
             the single result if self.targets is an integer engine id
         """
         args = [] if args is None else args
         kwargs = {} if kwargs is None else kwargs
         block = self.block if block is None else block
         track = self.track if track is None else track
         targets = self.targets if targets is None else targets
 
         _idents = self.client._build_targets(targets)[0]
         msg_ids = []
         trackers = []
         for ident in _idents:
             msg = self.client.send_apply_request(self._socket, f, args, kwargs, track=track,
                                     ident=ident)
             if track:
                 trackers.append(msg['tracker'])
             msg_ids.append(msg['header']['msg_id'])
         tracker = None if track is False else zmq.MessageTracker(*trackers)
         ar = AsyncResult(self.client, msg_ids, fname=getname(f), targets=targets, tracker=tracker)
         if block:
             try:
                 return ar.get()
             except KeyboardInterrupt:
                 pass
         return ar
 
 
     @spin_after
     def map(self, f, *sequences, **kwargs):
         """view.map(f, *sequences, block=self.block) => list|AsyncMapResult
 
         Parallel version of builtin `map`, using this View's `targets`.
 
         There will be one task per target, so work will be chunked
         if the sequences are longer than `targets`.
 
         Results can be iterated as they are ready, but will become available in chunks.
 
         Parameters
         ----------
 
         f : callable
             function to be mapped
         *sequences: one or more sequences of matching length
             the sequences to be distributed and passed to `f`
         block : bool
             whether to wait for the result or not [default self.block]
 
         Returns
         -------
 
         if block=False:
             AsyncMapResult
                 An object like AsyncResult, but which reassembles the sequence of results
                 into a single list. AsyncMapResults can be iterated through before all
                 results are complete.
         else:
             list
                 the result of map(f,*sequences)
         """
 
         block = kwargs.pop('block', self.block)
         for k in kwargs.keys():
             if k not in ['block', 'track']:
                 raise TypeError("invalid keyword arg, %r"%k)
 
         assert len(sequences) > 0, "must have some sequences to map onto!"
         pf = ParallelFunction(self, f, block=block, **kwargs)
         return pf.map(*sequences)
 
     @sync_results
     @save_ids
     def execute(self, code, silent=True, targets=None, block=None):
         """Executes `code` on `targets` in blocking or nonblocking manner.
 
         ``execute`` is always `bound` (affects engine namespace)
 
         Parameters
         ----------
 
         code : str
                 the code string to be executed
         block : bool
                 whether or not to wait until done to return
                 default: self.block
         """
         block = self.block if block is None else block
         targets = self.targets if targets is None else targets
 
         _idents = self.client._build_targets(targets)[0]
         msg_ids = []
         trackers = []
         for ident in _idents:
             msg = self.client.send_execute_request(self._socket, code, silent=silent, ident=ident)
             msg_ids.append(msg['header']['msg_id'])
         ar = AsyncResult(self.client, msg_ids, fname='execute', targets=targets)
         if block:
             try:
                 ar.get()
             except KeyboardInterrupt:
                 pass
         return ar
 
     def run(self, filename, targets=None, block=None):
         """Execute contents of `filename` on my engine(s).
 
         This simply reads the contents of the file and calls `execute`.
 
         Parameters
         ----------
 
         filename : str
                 The path to the file
         targets : int/str/list of ints/strs
                 the engines on which to execute
                 default : all
         block : bool
                 whether or not to wait until done
                 default: self.block
 
         """
         with open(filename, 'r') as f:
             # add newline in case of trailing indented whitespace
             # which will cause SyntaxError
             code = f.read()+'\n'
         return self.execute(code, block=block, targets=targets)
 
     def update(self, ns):
         """update remote namespace with dict `ns`
 
         See `push` for details.
         """
         return self.push(ns, block=self.block, track=self.track)
 
     def push(self, ns, targets=None, block=None, track=None):
         """update remote namespace with dict `ns`
 
         Parameters
         ----------
 
         ns : dict
             dict of keys with which to update engine namespace(s)
         block : bool [default : self.block]
             whether to wait to be notified of engine receipt
 
         """
 
         block = block if block is not None else self.block
         track = track if track is not None else self.track
         targets = targets if targets is not None else self.targets
         # applier = self.apply_sync if block else self.apply_async
         if not isinstance(ns, dict):
             raise TypeError("Must be a dict, not %s"%type(ns))
         return self._really_apply(util._push, kwargs=ns, block=block, track=track, targets=targets)
 
     def get(self, key_s):
         """get object(s) by `key_s` from remote namespace
 
         see `pull` for details.
         """
         # block = block if block is not None else self.block
         return self.pull(key_s, block=True)
 
     def pull(self, names, targets=None, block=None):
         """get object(s) by `name` from remote namespace
 
         will return one object if it is a key.
         can also take a list of keys, in which case it will return a list of objects.
         """
         block = block if block is not None else self.block
         targets = targets if targets is not None else self.targets
         applier = self.apply_sync if block else self.apply_async
         if isinstance(names, basestring):
             pass
         elif isinstance(names, (list,tuple,set)):
             for key in names:
                 if not isinstance(key, basestring):
                     raise TypeError("keys must be str, not type %r"%type(key))
         else:
             raise TypeError("names must be strs, not %r"%names)
         return self._really_apply(util._pull, (names,), block=block, targets=targets)
 
     def scatter(self, key, seq, dist='b', flatten=False, targets=None, block=None, track=None):
         """
         Partition a Python sequence and send the partitions to a set of engines.
         """
         block = block if block is not None else self.block
         track = track if track is not None else self.track
         targets = targets if targets is not None else self.targets
         
         # construct integer ID list:
         targets = self.client._build_targets(targets)[1]
 
         mapObject = Map.dists[dist]()
         nparts = len(targets)
         msg_ids = []
         trackers = []
         for index, engineid in enumerate(targets):
             partition = mapObject.getPartition(seq, index, nparts)
             if flatten and len(partition) == 1:
                 ns = {key: partition[0]}
             else:
                 ns = {key: partition}
             r = self.push(ns, block=False, track=track, targets=engineid)
             msg_ids.extend(r.msg_ids)
             if track:
                 trackers.append(r._tracker)
 
         if track:
             tracker = zmq.MessageTracker(*trackers)
         else:
             tracker = None
 
         r = AsyncResult(self.client, msg_ids, fname='scatter', targets=targets, tracker=tracker)
         if block:
             r.wait()
         else:
             return r
 
     @sync_results
     @save_ids
     def gather(self, key, dist='b', targets=None, block=None):
         """
         Gather a partitioned sequence on a set of engines as a single local seq.
         """
         block = block if block is not None else self.block
         targets = targets if targets is not None else self.targets
         mapObject = Map.dists[dist]()
         msg_ids = []
 
         # construct integer ID list:
         targets = self.client._build_targets(targets)[1]
         
         for index, engineid in enumerate(targets):
             msg_ids.extend(self.pull(key, block=False, targets=engineid).msg_ids)
 
         r = AsyncMapResult(self.client, msg_ids, mapObject, fname='gather')
 
         if block:
             try:
                 return r.get()
             except KeyboardInterrupt:
                 pass
         return r
 
     def __getitem__(self, key):
         return self.get(key)
 
     def __setitem__(self,key, value):
         self.update({key:value})
 
     def clear(self, targets=None, block=False):
         """Clear the remote namespaces on my engines."""
         block = block if block is not None else self.block
         targets = targets if targets is not None else self.targets
         return self.client.clear(targets=targets, block=block)
 
     def kill(self, targets=None, block=True):
         """Kill my engines."""
         block = block if block is not None else self.block
         targets = targets if targets is not None else self.targets
         return self.client.kill(targets=targets, block=block)
 
     #----------------------------------------
     # activate for %px,%autopx magics
     #----------------------------------------
     def activate(self):
         """Make this `View` active for parallel magic commands.
 
         IPython has a magic command syntax to work with `MultiEngineClient` objects.
         In a given IPython session there is a single active one.  While
         there can be many `Views` created and used by the user,
         there is only one active one.  The active `View` is used whenever
         the magic commands %px and %autopx are used.
 
         The activate() method is called on a given `View` to make it
         active.  Once this has been done, the magic commands can be used.
         """
 
         try:
             # This is injected into __builtins__.
             ip = get_ipython()
         except NameError:
             print "The IPython parallel magics (%result, %px, %autopx) only work within IPython."
         else:
             pmagic = ip.plugin_manager.get_plugin('parallelmagic')
             if pmagic is None:
                 ip.magic_load_ext('parallelmagic')
                 pmagic = ip.plugin_manager.get_plugin('parallelmagic')
 
             pmagic.active_view = self
 
 
 @skip_doctest
 class LoadBalancedView(View):
     """An load-balancing View that only executes via the Task scheduler.
 
     Load-balanced views can be created with the client's `view` method:
 
     >>> v = client.load_balanced_view()
 
     or targets can be specified, to restrict the potential destinations:
 
     >>> v = client.client.load_balanced_view([1,3])
 
     which would restrict loadbalancing to between engines 1 and 3.
 
     """
 
     follow=Any()
     after=Any()
     timeout=CFloat()
     retries = Integer(0)
 
     _task_scheme = Any()
     _flag_names = List(['targets', 'block', 'track', 'follow', 'after', 'timeout', 'retries'])
 
     def __init__(self, client=None, socket=None, **flags):
         super(LoadBalancedView, self).__init__(client=client, socket=socket, **flags)
         self._task_scheme=client._task_scheme
 
     def _validate_dependency(self, dep):
         """validate a dependency.
 
         For use in `set_flags`.
         """
         if dep is None or isinstance(dep, (basestring, AsyncResult, Dependency)):
             return True
         elif isinstance(dep, (list,set, tuple)):
             for d in dep:
                 if not isinstance(d, (basestring, AsyncResult)):
                     return False
         elif isinstance(dep, dict):
             if set(dep.keys()) != set(Dependency().as_dict().keys()):
                 return False
             if not isinstance(dep['msg_ids'], list):
                 return False
             for d in dep['msg_ids']:
                 if not isinstance(d, basestring):
                     return False
         else:
             return False
 
         return True
 
     def _render_dependency(self, dep):
         """helper for building jsonable dependencies from various input forms."""
         if isinstance(dep, Dependency):
             return dep.as_dict()
         elif isinstance(dep, AsyncResult):
             return dep.msg_ids
         elif dep is None:
             return []
         else:
             # pass to Dependency constructor
             return list(Dependency(dep))
 
     def set_flags(self, **kwargs):
         """set my attribute flags by keyword.
 
         A View is a wrapper for the Client's apply method, but with attributes
         that specify keyword arguments, those attributes can be set by keyword
         argument with this method.
 
         Parameters
         ----------
 
         block : bool
             whether to wait for results
         track : bool
             whether to create a MessageTracker to allow the user to
             safely edit after arrays and buffers during non-copying
             sends.
 
         after : Dependency or collection of msg_ids
             Only for load-balanced execution (targets=None)
             Specify a list of msg_ids as a time-based dependency.
             This job will only be run *after* the dependencies
             have been met.
 
         follow : Dependency or collection of msg_ids
             Only for load-balanced execution (targets=None)
             Specify a list of msg_ids as a location-based dependency.
             This job will only be run on an engine where this dependency
             is met.
 
         timeout : float/int or None
             Only for load-balanced execution (targets=None)
             Specify an amount of time (in seconds) for the scheduler to
             wait for dependencies to be met before failing with a
             DependencyTimeout.
 
         retries : int
             Number of times a task will be retried on failure.
         """
 
         super(LoadBalancedView, self).set_flags(**kwargs)
         for name in ('follow', 'after'):
             if name in kwargs:
                 value = kwargs[name]
                 if self._validate_dependency(value):
                     setattr(self, name, value)
                 else:
                     raise ValueError("Invalid dependency: %r"%value)
         if 'timeout' in kwargs:
             t = kwargs['timeout']
             if not isinstance(t, (int, long, float, type(None))):
                 raise TypeError("Invalid type for timeout: %r"%type(t))
             if t is not None:
                 if t < 0:
                     raise ValueError("Invalid timeout: %s"%t)
             self.timeout = t
 
     @sync_results
     @save_ids
     def _really_apply(self, f, args=None, kwargs=None, block=None, track=None,
                                         after=None, follow=None, timeout=None,
                                         targets=None, retries=None):
         """calls f(*args, **kwargs) on a remote engine, returning the result.
 
         This method temporarily sets all of `apply`'s flags for a single call.
 
         Parameters
         ----------
 
         f : callable
 
         args : list [default: empty]
 
         kwargs : dict [default: empty]
 
         block : bool [default: self.block]
             whether to block
         track : bool [default: self.track]
             whether to ask zmq to track the message, for safe non-copying sends
 
         !!!!!! TODO: THE REST HERE  !!!!
 
         Returns
         -------
 
         if self.block is False:
             returns AsyncResult
         else:
             returns actual result of f(*args, **kwargs) on the engine(s)
             This will be a list of self.targets is also a list (even length 1), or
             the single result if self.targets is an integer engine id
         """
 
         # validate whether we can run
         if self._socket.closed:
             msg = "Task farming is disabled"
             if self._task_scheme == 'pure':
                 msg += " because the pure ZMQ scheduler cannot handle"
                 msg += " disappearing engines."
             raise RuntimeError(msg)
 
         if self._task_scheme == 'pure':
             # pure zmq scheme doesn't support extra features
             msg = "Pure ZMQ scheduler doesn't support the following flags:"
             "follow, after, retries, targets, timeout"
             if (follow or after or retries or targets or timeout):
                 # hard fail on Scheduler flags
                 raise RuntimeError(msg)
             if isinstance(f, dependent):
                 # soft warn on functional dependencies
                 warnings.warn(msg, RuntimeWarning)
 
         # build args
         args = [] if args is None else args
         kwargs = {} if kwargs is None else kwargs
         block = self.block if block is None else block
         track = self.track if track is None else track
         after = self.after if after is None else after
         retries = self.retries if retries is None else retries
         follow = self.follow if follow is None else follow
         timeout = self.timeout if timeout is None else timeout
         targets = self.targets if targets is None else targets
 
         if not isinstance(retries, int):
             raise TypeError('retries must be int, not %r'%type(retries))
 
         if targets is None:
             idents = []
         else:
             idents = self.client._build_targets(targets)[0]
             # ensure *not* bytes
             idents = [ ident.decode() for ident in idents ]
 
         after = self._render_dependency(after)
         follow = self._render_dependency(follow)
         subheader = dict(after=after, follow=follow, timeout=timeout, targets=idents, retries=retries)
 
         msg = self.client.send_apply_request(self._socket, f, args, kwargs, track=track,
                                 subheader=subheader)
         tracker = None if track is False else msg['tracker']
 
         ar = AsyncResult(self.client, msg['header']['msg_id'], fname=getname(f), targets=None, tracker=tracker)
 
         if block:
             try:
                 return ar.get()
             except KeyboardInterrupt:
                 pass
         return ar
 
     @spin_after
     @save_ids
     def map(self, f, *sequences, **kwargs):
         """view.map(f, *sequences, block=self.block, chunksize=1, ordered=True) => list|AsyncMapResult
 
         Parallel version of builtin `map`, load-balanced by this View.
 
         `block`, and `chunksize` can be specified by keyword only.
 
         Each `chunksize` elements will be a separate task, and will be
         load-balanced. This lets individual elements be available for iteration
         as soon as they arrive.
 
         Parameters
         ----------
 
         f : callable
             function to be mapped
         *sequences: one or more sequences of matching length
             the sequences to be distributed and passed to `f`
         block : bool [default self.block]
             whether to wait for the result or not
         track : bool
             whether to create a MessageTracker to allow the user to
             safely edit after arrays and buffers during non-copying
             sends.
         chunksize : int [default 1]
             how many elements should be in each task.
         ordered : bool [default True]
             Whether the results should be gathered as they arrive, or enforce
             the order of submission.
             
             Only applies when iterating through AsyncMapResult as results arrive.
             Has no effect when block=True.
 
         Returns
         -------
 
         if block=False:
             AsyncMapResult
                 An object like AsyncResult, but which reassembles the sequence of results
                 into a single list. AsyncMapResults can be iterated through before all
                 results are complete.
             else:
                 the result of map(f,*sequences)
 
         """
 
         # default
         block = kwargs.get('block', self.block)
         chunksize = kwargs.get('chunksize', 1)
         ordered = kwargs.get('ordered', True)
 
         keyset = set(kwargs.keys())
         extra_keys = keyset.difference_update(set(['block', 'chunksize']))
         if extra_keys:
             raise TypeError("Invalid kwargs: %s"%list(extra_keys))
 
         assert len(sequences) > 0, "must have some sequences to map onto!"
 
         pf = ParallelFunction(self, f, block=block, chunksize=chunksize, ordered=ordered)
         return pf.map(*sequences)
 
 __all__ = ['LoadBalancedView', 'DirectView']

IPython/parallel/tests/test_view.py

@@ -1,553 +1,571 b''
 # -*- coding: utf-8 -*-
 """test View objects
 
 Authors:
 
 * Min RK
 """
 #-------------------------------------------------------------------------------
 #  Copyright (C) 2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-------------------------------------------------------------------------------
 
 #-------------------------------------------------------------------------------
 # Imports
 #-------------------------------------------------------------------------------
 
 import sys
 import time
 from tempfile import mktemp
 from StringIO import StringIO
 
 import zmq
 from nose import SkipTest
 
 from IPython.testing import decorators as dec
+from IPython.testing.ipunittest import ParametricTestCase
 
 from IPython import parallel  as pmod
 from IPython.parallel import error
 from IPython.parallel import AsyncResult, AsyncHubResult, AsyncMapResult
 from IPython.parallel import DirectView
 from IPython.parallel.util import interactive
 
 from IPython.parallel.tests import add_engines
 
 from .clienttest import ClusterTestCase, crash, wait, skip_without
 
 def setup():
     add_engines(3, total=True)
 
-class TestView(ClusterTestCase):
+class TestView(ClusterTestCase, ParametricTestCase):
     
     def test_z_crash_mux(self):
         """test graceful handling of engine death (direct)"""
         raise SkipTest("crash tests disabled, due to undesirable crash reports")
         # self.add_engines(1)
         eid = self.client.ids[-1]
         ar = self.client[eid].apply_async(crash)
         self.assertRaisesRemote(error.EngineError, ar.get, 10)
         eid = ar.engine_id
         tic = time.time()
         while eid in self.client.ids and time.time()-tic < 5:
             time.sleep(.01)
             self.client.spin()
         self.assertFalse(eid in self.client.ids, "Engine should have died")
     
     def test_push_pull(self):
         """test pushing and pulling"""
         data = dict(a=10, b=1.05, c=range(10), d={'e':(1,2),'f':'hi'})
         t = self.client.ids[-1]
         v = self.client[t]
         push = v.push
         pull = v.pull
         v.block=True
         nengines = len(self.client)
         push({'data':data})
         d = pull('data')
         self.assertEquals(d, data)
         self.client[:].push({'data':data})
         d = self.client[:].pull('data', block=True)
         self.assertEquals(d, nengines*[data])
         ar = push({'data':data}, block=False)
         self.assertTrue(isinstance(ar, AsyncResult))
         r = ar.get()
         ar = self.client[:].pull('data', block=False)
         self.assertTrue(isinstance(ar, AsyncResult))
         r = ar.get()
         self.assertEquals(r, nengines*[data])
         self.client[:].push(dict(a=10,b=20))
         r = self.client[:].pull(('a','b'), block=True)
         self.assertEquals(r, nengines*[[10,20]])
     
     def test_push_pull_function(self):
         "test pushing and pulling functions"
         def testf(x):
             return 2.0*x
         
         t = self.client.ids[-1]
         v = self.client[t]
         v.block=True
         push = v.push
         pull = v.pull
         execute = v.execute
         push({'testf':testf})
         r = pull('testf')
         self.assertEqual(r(1.0), testf(1.0))
         execute('r = testf(10)')
         r = pull('r')
         self.assertEquals(r, testf(10))
         ar = self.client[:].push({'testf':testf}, block=False)
         ar.get()
         ar = self.client[:].pull('testf', block=False)
         rlist = ar.get()
         for r in rlist:
             self.assertEqual(r(1.0), testf(1.0))
         execute("def g(x): return x*x")
         r = pull(('testf','g'))
         self.assertEquals((r[0](10),r[1](10)), (testf(10), 100))
     
     def test_push_function_globals(self):
         """test that pushed functions have access to globals"""
         @interactive
         def geta():
             return a
         # self.add_engines(1)
         v = self.client[-1]
         v.block=True
         v['f'] = geta
         self.assertRaisesRemote(NameError, v.execute, 'b=f()')
         v.execute('a=5')
         v.execute('b=f()')
         self.assertEquals(v['b'], 5)
     
     def test_push_function_defaults(self):
         """test that pushed functions preserve default args"""
         def echo(a=10):
             return a
         v = self.client[-1]
         v.block=True
         v['f'] = echo
         v.execute('b=f()')
         self.assertEquals(v['b'], 10)
 
     def test_get_result(self):
         """test getting results from the Hub."""
         c = pmod.Client(profile='iptest')
         # self.add_engines(1)
         t = c.ids[-1]
         v = c[t]
         v2 = self.client[t]
         ar = v.apply_async(wait, 1)
         # give the monitor time to notice the message
         time.sleep(.25)
         ahr = v2.get_result(ar.msg_ids)
         self.assertTrue(isinstance(ahr, AsyncHubResult))
         self.assertEquals(ahr.get(), ar.get())
         ar2 = v2.get_result(ar.msg_ids)
         self.assertFalse(isinstance(ar2, AsyncHubResult))
         c.spin()
         c.close()
     
     def test_run_newline(self):
         """test that run appends newline to files"""
         tmpfile = mktemp()
         with open(tmpfile, 'w') as f:
             f.write("""def g():
                 return 5
                 """)
         v = self.client[-1]
         v.run(tmpfile, block=True)
         self.assertEquals(v.apply_sync(lambda f: f(), pmod.Reference('g')), 5)
 
     def test_apply_tracked(self):
         """test tracking for apply"""
         # self.add_engines(1)
         t = self.client.ids[-1]
         v = self.client[t]
         v.block=False
         def echo(n=1024*1024, **kwargs):
             with v.temp_flags(**kwargs):
                 return v.apply(lambda x: x, 'x'*n)
         ar = echo(1, track=False)
         self.assertTrue(isinstance(ar._tracker, zmq.MessageTracker))
         self.assertTrue(ar.sent)
         ar = echo(track=True)
         self.assertTrue(isinstance(ar._tracker, zmq.MessageTracker))
         self.assertEquals(ar.sent, ar._tracker.done)
         ar._tracker.wait()
         self.assertTrue(ar.sent)
         
     def test_push_tracked(self):
         t = self.client.ids[-1]
         ns = dict(x='x'*1024*1024)
         v = self.client[t]
         ar = v.push(ns, block=False, track=False)
         self.assertTrue(isinstance(ar._tracker, zmq.MessageTracker))
         self.assertTrue(ar.sent)
         
         ar = v.push(ns, block=False, track=True)
         self.assertTrue(isinstance(ar._tracker, zmq.MessageTracker))
         ar._tracker.wait()
         self.assertEquals(ar.sent, ar._tracker.done)
         self.assertTrue(ar.sent)
         ar.get()
         
     def test_scatter_tracked(self):
         t = self.client.ids
         x='x'*1024*1024
         ar = self.client[t].scatter('x', x, block=False, track=False)
         self.assertTrue(isinstance(ar._tracker, zmq.MessageTracker))
         self.assertTrue(ar.sent)
         
         ar = self.client[t].scatter('x', x, block=False, track=True)
         self.assertTrue(isinstance(ar._tracker, zmq.MessageTracker))
         self.assertEquals(ar.sent, ar._tracker.done)
         ar._tracker.wait()
         self.assertTrue(ar.sent)
         ar.get()
     
     def test_remote_reference(self):
         v = self.client[-1]
         v['a'] = 123
         ra = pmod.Reference('a')
         b = v.apply_sync(lambda x: x, ra)
         self.assertEquals(b, 123)
 
 
     def test_scatter_gather(self):
         view = self.client[:]
         seq1 = range(16)
         view.scatter('a', seq1)
         seq2 = view.gather('a', block=True)
         self.assertEquals(seq2, seq1)
         self.assertRaisesRemote(NameError, view.gather, 'asdf', block=True)
     
     @skip_without('numpy')
     def test_scatter_gather_numpy(self):
         import numpy
         from numpy.testing.utils import assert_array_equal, assert_array_almost_equal
         view = self.client[:]
         a = numpy.arange(64)
         view.scatter('a', a)
         b = view.gather('a', block=True)
         assert_array_equal(b, a)
     
     def test_scatter_gather_lazy(self):
         """scatter/gather with targets='all'"""
         view = self.client.direct_view(targets='all')
         x = range(64)
         view.scatter('x', x)
         gathered = view.gather('x', block=True)
         self.assertEquals(gathered, x)
         
 
     @dec.known_failure_py3
     @skip_without('numpy')
     def test_push_numpy_nocopy(self):
         import numpy
         view = self.client[:]
         a = numpy.arange(64)
         view['A'] = a
         @interactive
         def check_writeable(x):
             return x.flags.writeable
         
         for flag in view.apply_sync(check_writeable, pmod.Reference('A')):
             self.assertFalse(flag, "array is writeable, push shouldn't have pickled it")
         
         view.push(dict(B=a))
         for flag in view.apply_sync(check_writeable, pmod.Reference('B')):
             self.assertFalse(flag, "array is writeable, push shouldn't have pickled it")
     
     @skip_without('numpy')
     def test_apply_numpy(self):
         """view.apply(f, ndarray)"""
         import numpy
         from numpy.testing.utils import assert_array_equal, assert_array_almost_equal
         
         A = numpy.random.random((100,100))
         view = self.client[-1]
         for dt in [ 'int32', 'uint8', 'float32', 'float64' ]:
             B = A.astype(dt)
             C = view.apply_sync(lambda x:x, B)
             assert_array_equal(B,C)
     
     def test_map(self):
         view = self.client[:]
         def f(x):
             return x**2
         data = range(16)
         r = view.map_sync(f, data)
         self.assertEquals(r, map(f, data))
     
     def test_map_iterable(self):
         """test map on iterables (direct)"""
         view = self.client[:]
         # 101 is prime, so it won't be evenly distributed
         arr = range(101)
         # ensure it will be an iterator, even in Python 3
         it = iter(arr)
         r = view.map_sync(lambda x:x, arr)
         self.assertEquals(r, list(arr))
     
     def test_scatterGatherNonblocking(self):
         data = range(16)
         view = self.client[:]
         view.scatter('a', data, block=False)
         ar = view.gather('a', block=False)
         self.assertEquals(ar.get(), data)
     
     @skip_without('numpy')
     def test_scatter_gather_numpy_nonblocking(self):
         import numpy
         from numpy.testing.utils import assert_array_equal, assert_array_almost_equal
         a = numpy.arange(64)
         view = self.client[:]
         ar = view.scatter('a', a, block=False)
         self.assertTrue(isinstance(ar, AsyncResult))
         amr = view.gather('a', block=False)
         self.assertTrue(isinstance(amr, AsyncMapResult))
         assert_array_equal(amr.get(), a)
 
     def test_execute(self):
         view = self.client[:]
         # self.client.debug=True
         execute = view.execute
         ar = execute('c=30', block=False)
         self.assertTrue(isinstance(ar, AsyncResult))
         ar = execute('d=[0,1,2]', block=False)
         self.client.wait(ar, 1)
         self.assertEquals(len(ar.get()), len(self.client))
         for c in view['c']:
             self.assertEquals(c, 30)
     
     def test_abort(self):
         view = self.client[-1]
         ar = view.execute('import time; time.sleep(1)', block=False)
         ar2 = view.apply_async(lambda : 2)
         ar3 = view.apply_async(lambda : 3)
         view.abort(ar2)
         view.abort(ar3.msg_ids)
         self.assertRaises(error.TaskAborted, ar2.get)
         self.assertRaises(error.TaskAborted, ar3.get)
     
     def test_abort_all(self):
         """view.abort() aborts all outstanding tasks"""
         view = self.client[-1]
         ars = [ view.apply_async(time.sleep, 0.25) for i in range(10) ]
         view.abort()
         view.wait(timeout=5)
         for ar in ars[5:]:
             self.assertRaises(error.TaskAborted, ar.get)
     
     def test_temp_flags(self):
         view = self.client[-1]
         view.block=True
         with view.temp_flags(block=False):
             self.assertFalse(view.block)
         self.assertTrue(view.block)
     
     @dec.known_failure_py3
     def test_importer(self):
         view = self.client[-1]
         view.clear(block=True)
         with view.importer:
             import re
         
         @interactive
         def findall(pat, s):
             # this globals() step isn't necessary in real code
             # only to prevent a closure in the test
             re = globals()['re']
             return re.findall(pat, s)
         
         self.assertEquals(view.apply_sync(findall, '\w+', 'hello world'), 'hello world'.split())
     
     # parallel magic tests
     
     def test_magic_px_blocking(self):
         ip = get_ipython()
         v = self.client[-1]
         v.activate()
         v.block=True
 
         ip.magic_px('a=5')
         self.assertEquals(v['a'], 5)
         ip.magic_px('a=10')
         self.assertEquals(v['a'], 10)
         sio = StringIO()
         savestdout = sys.stdout
         sys.stdout = sio
         # just 'print a' worst ~99% of the time, but this ensures that
         # the stdout message has arrived when the result is finished:
         ip.magic_px('import sys,time;print (a); sys.stdout.flush();time.sleep(0.2)')
         sys.stdout = savestdout
         buf = sio.getvalue()
         self.assertTrue('[stdout:' in buf, buf)
         self.assertTrue(buf.rstrip().endswith('10'))
         self.assertRaisesRemote(ZeroDivisionError, ip.magic_px, '1/0')
 
     def test_magic_px_nonblocking(self):
         ip = get_ipython()
         v = self.client[-1]
         v.activate()
         v.block=False
 
         ip.magic_px('a=5')
         self.assertEquals(v['a'], 5)
         ip.magic_px('a=10')
         self.assertEquals(v['a'], 10)
         sio = StringIO()
         savestdout = sys.stdout
         sys.stdout = sio
         ip.magic_px('print a')
         sys.stdout = savestdout
         buf = sio.getvalue()
         self.assertFalse('[stdout:%i]'%v.targets in buf)
         ip.magic_px('1/0')
         ar = v.get_result(-1)
         self.assertRaisesRemote(ZeroDivisionError, ar.get)
     
     def test_magic_autopx_blocking(self):
         ip = get_ipython()
         v = self.client[-1]
         v.activate()
         v.block=True
 
         sio = StringIO()
         savestdout = sys.stdout
         sys.stdout = sio
         ip.magic_autopx()
         ip.run_cell('\n'.join(('a=5','b=10','c=0')))
         ip.run_cell('b*=2')
         ip.run_cell('print (b)')
         ip.run_cell("b/c")
         ip.magic_autopx()
         sys.stdout = savestdout
         output = sio.getvalue().strip()
         self.assertTrue(output.startswith('%autopx enabled'))
         self.assertTrue(output.endswith('%autopx disabled'))
         self.assertTrue('RemoteError: ZeroDivisionError' in output)
         ar = v.get_result(-1)
         self.assertEquals(v['a'], 5)
         self.assertEquals(v['b'], 20)
         self.assertRaisesRemote(ZeroDivisionError, ar.get)
 
     def test_magic_autopx_nonblocking(self):
         ip = get_ipython()
         v = self.client[-1]
         v.activate()
         v.block=False
 
         sio = StringIO()
         savestdout = sys.stdout
         sys.stdout = sio
         ip.magic_autopx()
         ip.run_cell('\n'.join(('a=5','b=10','c=0')))
         ip.run_cell('print (b)')
         ip.run_cell("b/c")
         ip.run_cell('b*=2')
         ip.magic_autopx()
         sys.stdout = savestdout
         output = sio.getvalue().strip()
         self.assertTrue(output.startswith('%autopx enabled'))
         self.assertTrue(output.endswith('%autopx disabled'))
         self.assertFalse('ZeroDivisionError' in output)
         ar = v.get_result(-2)
         self.assertEquals(v['a'], 5)
         self.assertEquals(v['b'], 20)
         self.assertRaisesRemote(ZeroDivisionError, ar.get)
     
     def test_magic_result(self):
         ip = get_ipython()
         v = self.client[-1]
         v.activate()
         v['a'] = 111
         ra = v['a']
         
         ar = ip.magic_result()
         self.assertEquals(ar.msg_ids, [v.history[-1]])
         self.assertEquals(ar.get(), 111)
         ar = ip.magic_result('-2')
         self.assertEquals(ar.msg_ids, [v.history[-2]])
     
     def test_unicode_execute(self):
         """test executing unicode strings"""
         v = self.client[-1]
         v.block=True
         if sys.version_info[0] >= 3:
             code="a='é'"
         else:
             code=u"a=u'é'"
         v.execute(code)
         self.assertEquals(v['a'], u'é')
         
     def test_unicode_apply_result(self):
         """test unicode apply results"""
         v = self.client[-1]
         r = v.apply_sync(lambda : u'é')
         self.assertEquals(r, u'é')
     
     def test_unicode_apply_arg(self):
         """test passing unicode arguments to apply"""
         v = self.client[-1]
         
         @interactive
         def check_unicode(a, check):
             assert isinstance(a, unicode), "%r is not unicode"%a
             assert isinstance(check, bytes), "%r is not bytes"%check
             assert a.encode('utf8') == check, "%s != %s"%(a,check)
         
         for s in [ u'é', u'ßø®∫',u'asdf' ]:
             try:
                 v.apply_sync(check_unicode, s, s.encode('utf8'))
             except error.RemoteError as e:
                 if e.ename == 'AssertionError':
                     self.fail(e.evalue)
                 else:
                     raise e
     
     def test_map_reference(self):
         """view.map(<Reference>, *seqs) should work"""
         v = self.client[:]
         v.scatter('n', self.client.ids, flatten=True)
         v.execute("f = lambda x,y: x*y")
         rf = pmod.Reference('f')
         nlist = list(range(10))
         mlist = nlist[::-1]
         expected = [ m*n for m,n in zip(mlist, nlist) ]
         result = v.map_sync(rf, mlist, nlist)
         self.assertEquals(result, expected)
 
     def test_apply_reference(self):
         """view.apply(<Reference>, *args) should work"""
         v = self.client[:]
         v.scatter('n', self.client.ids, flatten=True)
         v.execute("f = lambda x: n*x")
         rf = pmod.Reference('f')
         result = v.apply_sync(rf, 5)
         expected = [ 5*id for id in self.client.ids ]
         self.assertEquals(result, expected)
     
     def test_eval_reference(self):
         v = self.client[self.client.ids[0]]
         v['g'] = range(5)
         rg = pmod.Reference('g[0]')
         echo = lambda x:x
         self.assertEquals(v.apply_sync(echo, rg), 0)
     
     def test_reference_nameerror(self):
         v = self.client[self.client.ids[0]]
         r = pmod.Reference('elvis_has_left')
         echo = lambda x:x
         self.assertRaisesRemote(NameError, v.apply_sync, echo, r)
 
     def test_single_engine_map(self):
         e0 = self.client[self.client.ids[0]]
         r = range(5)
         check = [ -1*i for i in r ]
         result = e0.map_sync(lambda x: -1*x, r)
         self.assertEquals(result, check)
+    
+    def test_len(self):
+        """len(view) makes sense"""
+        e0 = self.client[self.client.ids[0]]
+        yield self.assertEquals(len(e0), 1)
+        v = self.client[:]
+        yield self.assertEquals(len(v), len(self.client.ids))
+        v = self.client.direct_view('all')
+        yield self.assertEquals(len(v), len(self.client.ids))
+        v = self.client[:2]
+        yield self.assertEquals(len(v), 2)
+        v = self.client[:1]
+        yield self.assertEquals(len(v), 1)
+        v = self.client.load_balanced_view()
+        yield self.assertEquals(len(v), len(self.client.ids))
+        # parametric tests seem to require manual closing?
+        self.client.close()