arthur-tacca

// Moved to:
// https://github.com/arthur-tacca/dart-cancel-examples/blob/main/lib/abort.dart

arthur-tacca

Proposal to Add Cancellation Tokens to Dart

Part of what makes Dart great is its excellent async support, but it is in dire need of a unified mechanism for cancellation.

Currently, there are a variety of inconsistent cancellation APIs for different operations (e.g. ConnectionTask for Socket.startConnect(), StreamSubscription.cancel(), HttpClientRequest.abort()), and some lack any cancellation support at all (most notoriously, HttpClient.getUrl() as noted in dart-lang/sdk#51267). The facilities to write your own cancellable operations (CancelableCompleter to build a [CancelableOperation

arthur-tacca

# Adapted with permission from the EdgeDB project;
# license: PSFL.


__all__ = ("TaskGroup",)

from . import events
from . import exceptions
from . import tasks

arthur-tacca

# Question: if we cancel a scope, and another task is active in that scope, is it *guaranteed* that
# it will raise CancelledError when it next wakes? (Even if it is already queued to wake for some
# other reason.)
#
# The answer, at least in practice, is no: in this example, send_and_cancel() sends some data to
# a memory channel then cancels a scope, and then receive() (which is running in that scope) wakes
# with the first value that was sent.
#
# On my computer, this code produces the following output:
#

arthur-tacca

# Illustration of missed cleanup in an asyncio task group due to the way it
# cancels a task that has not started by never running it at all. See issue:
# https://github.com/python/cpython/issues/116048
#
# When run on my computer, I usually get the output:
#
#     Total connections created: 3300
#     Connections left unclosed: 0
#
# i.e., all connections that were created were cleaned up. But sometimes I get:

arthur-tacca

# aioresult variant of StreamResultsNursery
# Original idea by smurfix: https://gist.github.com/smurfix/0130817fa5ba6d3bb4a0f00e4d93cf86
# Fixed non-aioresult version: https://gist.github.com/arthur-tacca/6c676a21d0dcc0582edb50c9c2aa3e3c


from collections import deque
import math

from aioresult import ResultCapture
import trio

arthur-tacca

# Original idea by smurfix: https://gist.github.com/smurfix/0130817fa5ba6d3bb4a0f00e4d93cf86
# aioresult variant: https://gist.github.com/arthur-tacca/5c717ae68ac037e72ae45fd1e9ca1345

from collections import deque
import math
import trio


class StreamResultsNursery:
    def __init__(self, max_running_tasks=math.inf):

arthur-tacca

#
#  -- An improved version of this code is now in the aioresult library --
#
# https://github.com/arthur-tacca/aioresult
#
#
# - aioresult has a ResultCapture class similar to the one below
# - It also has a Future class that allows manually setting the result, which shares a base class with ResultCapture
# - There is a utility function with a similar effect to StartableResultCapture below (but much simpler)
# - There are utility functions wait_any(), wait_all() and to_channel() (which also work with Future instances)

arthur-tacca

// Like solution 4, but uses a dummy Node object for leaf nodes instead of *this
// The implicitly declared constructor is fine because we don't need to fix up *this

class Node
{
public:
    Node(int d, Pool& pool)
        : level{d}
        , l{d > 0 ? pool.emplace_back(Node(d - 1, pool)) : dummy}
        , r{d > 0 ? pool.emplace_back(Node(d - 1, pool)) : dummy}

arthur-tacca

#!/usr/bin/env python

from setuptools import setup

setup(
    name="caffe",
    version='1.0rc3',
    url='https://github.com/BVLC/caffe',
    license='BSD',
    description=('Caffe is a deep learning framework made with expression, '