threadのお勉強(with python) - 空飛ぶロボットのつくりかた

ROS x thread x pythonのコードを読みながらthreadの理解、実装方法を学ぶ

python並列化

threading.Thread
multiprocessing.Process

Pythonのマルチスレッド処理：threading, multiprocessing | UX MILK

ROS x thread x pythonのコード

jsk_robot/OdometryFeedbackWrapper.py at master · jsk-ros-pkg/jsk_robot · GitHub

self.lock = threading.Lock()

~

def source_odom_callback(self, msg):
    with self.lock:
    ~

のようにlockを用いてthread safeを実現

    def feedback_odom_callback(self, msg):
        if not self.odom:
            return
        self.feedback_odom = msg
        with self.lock:
            # check distribution accuracy
            nearest_odom = copy.deepcopy(self.odom)
            nearest_dt = (self.feedback_odom.header.stamp - self.odom.header.stamp).to_sec()

lockした状態のself.odomの中身を深いcopyでnearest_odomに格納。

参考：Python の threading.Lock を試してみる | CUBE SUGAR STORAGE

dynamic_reconfigure/server.py at master · ros/dynamic_reconfigure · GitHub

mutex: 排他制御　 http://wa3.i-3-i.info/word13360.html

上記と同じ。lockを使用。

ドローン画像取得 (Erle-Copter, ArduPilot) - Qiita

from threading import Thread, Lock
VERBOSE=True
import copy
mutex = Lock()
topic_name = "/camera/image/compressed"
class web_video_server:
    def __init__(self):
        '''Initialize ros publisher, ros subscriber'''
        # subscribed Topic
        self.subscriber = rospy.Subscriber(topic_name,
            CompressedImage, self.callback,  queue_size = 1)
        if VERBOSE :
            print "subscribed to " + topic_name
    def getCompressedImage(self):
        mutex.acquire(1)
        result = copy.deepcopy(self.np_arr);
        mutex.release()
        return result;
    def callback(self, ros_data):
        '''Callback function of subscribed topic. '''
        mutex.acquire(1)
        self.np_arr = ros_data.data;
        mutex.release()