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Use heapq.merge instead of custom merge sort code #2017

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merged 1 commit into from
Aug 12, 2020

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chaoflow
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@chaoflow chaoflow commented Aug 10, 2020

Since Python 3.5 a library function exists that does what we need. I'm therefore proposing to replace custom merge sort code with calls to heapq.merge.

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Is this good for melodic-devel? Shall I rebase to noetic-devel (and open a separate PR)?

@chaoflow chaoflow changed the base branch from melodic-devel to noetic-devel August 10, 2020 14:25
@chaoflow
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This needs at least python 3.5 and therefore cannot be used on melodic-devel.

The two failing checks, I don't understand.

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Please provide some context in the description of the PR why you are proposing this change.

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@dirk-thomas Just did.

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I couldn't find any documentation if heapq.merge is stable. Do you have any information on that?

Also what motivates the change? Is heapq.merge in any way better (e.g. faster) than the custom function?

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@dirk-thomas The heapq.merge implementation since python 3.5 https://github.com/python/cpython/blob/3.5/Lib/heapq.py is very similar to the the one in bag.py, with slight optimizations.

My motivation for the change is to replace custom code with equal or better code in Python's standard library.

In its current implementation it is stable. But given that it is not explicitly called merge sort, we should confirm with Python whether its stability can be taken granted also in future versions. I'm happy to do that if the change in general is desirable.

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It has been stable since it was added in 2.6 due to explicit code, not as a side effect. I think we can take it for granted that it will stay stable.

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Sounds good to me. Thanks for the patch.

@dirk-thomas dirk-thomas merged commit b8bc0b7 into ros:noetic-devel Aug 12, 2020
@chaoflow chaoflow deleted the heapq-merge branch August 12, 2020 18:15
nim65s added a commit to nim65s/robotpkg that referenced this pull request Mar 12, 2021
Because DEPEND_ABI.ros-comm.noetic?= ros-comm>=1.15

1.15.9 (2020-10-16)
-------------------
* Fix deadlock when service connection is dropped (ros/ros_comm#2074)
* Update maintainers (ros/ros_comm#2075)
* Fix case where accessing cached parameters shuts down another node (ros/ros_comm#2068)
* Fix spelling (ros/ros_comm#2066)
* Fix Lost Wake Bug in ROSOutAppender (ros/ros_comm#2033)
* Fix compatibility issue with boost 1.73 and above (ros/ros_comm#2023)
* Gracefully stop recording upon SIGTERM and SIGINT (ros/ros_comm#2038)
* Use heapq.merge instead of custom merge sort code (ros/ros_comm#2017)
* Fix handling of single quotes in command arguments on Windows (ros/ros_comm#2051)
* Clearer error message (ros/ros_comm#2035)
* Ignore underscores when parsing literal numeric values for Python 3 compatibility (ros/ros_comm#2022)
* Clear cached URI for a node that has gone offline (ros/ros_comm#2010)
* Add skip_cache parameter to rosnode_ping() (ros/ros_comm#2009)
* Install advertisetest (ros/ros_comm#2046)
* Use range instead of xrange for Python 3 compatibility (ros/ros_comm#2013)
* Fix to address CVE-2020-16124 (ros/ros_comm#2065)
* Fix XmlRpcValue::_doubleFormat being unused (ros/ros_comm#2003)

1.15.8 (2020-07-23)
-------------------
* change is_async_connected to use epoll when available (ros/ros_comm#1983)
* allow mixing latched and unlatched publishers (ros/ros_comm#1991)
* remove not existing NodeProxy from rospy __all_\_ (ros/ros_comm#2007)
* fix typo in topics.py (ros/ros_comm#1977)
* fix bad relative import (still Python 2 style) (ros/ros_comm#1973)
* improve shutdown message with duplicate node name (ros/ros_comm#1992)
* remove dependency on rostopic from rostest package (ros/ros_comm#2002)
* fix missing reload() function in Python 3 (ros/ros_comm#1968)
* add latch param to throttle (ros/ros_comm#1944)
* add const versions of XmlRpcValue converting operators (ros/ros_comm#1978)

1.15.7 (2020-05-28)
-------------------
* fix Windows build break (ros/ros_comm#1961)
* fix NameError in launch error handling (ros/ros_comm#1965)

1.15.6 (2020-05-21)
-------------------
* fix a bug that using a destroyed connection object (ros/ros_comm#1950)

1.15.5 (2020-05-15)
-------------------
* check if async socket connect is success or failure before TransportTCP::read() and TransportTCP::write() (ros/ros_comm#1954)
* fix bug that connection drop signal related funtion throw a bad_weak exception (ros/ros_comm#1940)
* multiple latched publishers per process on the same topic (ros/ros_comm#1544)
* fix negative numbers in ros statistics (ros/ros_comm#1531)
* remove extra \n in ROS_DEBUG (ros/ros_comm#1925)
* add option to repeat latched messages at the start of bag splits (ros/ros_comm#1850)
* fix bag migration failures caused by typo in connection_header assignment (ros/ros_comm#1952)
* fix brief description comments after members (ros/ros_comm#1920)
* add --sigint-timeout and --sigterm-timeout parameters (ros/ros_comm#1937)
* roslaunch-check: search dir recursively (ros/ros_comm#1914)
* sort printed nodes by namespace alphabetically (ros/ros_comm#1934)
* remove pycrypto import (not used) (ros/ros_comm#1922)
* avoid infinite recursion in rosrun tab completion when rosbash is not installed (ros/ros_comm#1948)
* fix bare pointer in topic_tools::ShapeShifter (ros/ros_comm#1722)
* clear message queue on simtime jumping back (ros/ros_comm#1518)
* use undefined dynamic_lookup on macOS (ros/ros_comm#1923)
* check if enough FDs are free, instead counting the total free FDs (ros/ros_comm#1929)

1.15.4 (2020-03-19)
-------------------
* restrict boost dependencies to components used (ros/ros_comm#1871)
* add exception for ConnectionAbortedError (ros/ros_comm#1908)
* fix mac trying to use epoll instead of kqueue (ros/ros_comm#1907)
* fix AttributeError: __exit__ (ros/ros_comm#1915, regression from 1.14.4)

1.15.3 (2020-02-28)
-------------------
* remove Boost version check since Noetic only targets platforms with 1.67+ (ros/ros_comm#1903)

1.15.2 (2020-02-25)
-------------------
* export missing Boost dependency (ros/ros_comm#1898)
* add timestamp formatting for rosconsole (ros/ros_comm#1892)

1.15.1 (2020-02-24)
-------------------
* fix missing boost dependencies (ros/ros_comm#1895)
* use setuptools instead of distutils (ros/ros_comm#1870)
* increase time limit of advertisetest/publishtest.test to reduce flakyness (ros/ros_comm#1897)

1.15.0 (2020-02-21)
-------------------
* fix dictionary changed size during iteration (ros/ros_comm#1894)
* update test to pass with old and new yaml (ros/ros_comm#1893)

Packaging changes:
- removed patch-an, as there are no more boost version checks
- updated patch-ao
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