dataassociator base类 enumerate_joint_hypotheses method简析

Posted 2021-03-11 iamhc

dataassociator base类 enumerate_joint_hypotheses function 实现如下

 1     @classmethod
 2     def enumerate_joint_hypotheses(cls, hypotheses):
 3         """Enumerate the possible joint hypotheses.
 4 
 5         Create a list of all possible joint hypotheses from the individual
 6         hypotheses and determine whether each is valid.
 7 
 8         Parameters
 9         ----------
10         hypotheses : list of :class:`Hypothesis`
11             A list of all hypotheses linking predictions to detections,
12             including missed detections
13 
14         Returns
15         -------
16         joint_hypotheses : list of :class:`JointHypothesis`
17             A list of all valid joint hypotheses with a score on each
18         """
19 
20         # Create a list of dictionaries of valid track-hypothesis pairs
21         joint_hypotheses = [
22             JointHypothesis({
23                 track: hypothesis
24                 for track, hypothesis in zip(hypotheses, joint_hypothesis)})
25             for joint_hypothesis in itertools.product(*hypotheses.values())
26             if cls.isvalid(joint_hypothesis)]
27 
28         return joint_hypotheses

hypotheses对象是一个字典，它的key是track，value是相对应的MultipleHypothesis。

这段代码实现的是从hypotheses。在这段代码中，有几个比较有意思的python用法。

1. itertools.product(*hypotheses.values())

   *hypotheses.values() 中*是unpack的用法。这样，itertools.product的input argument就是(MultipleHypothesis_1, MultipleHypothesis_2, ..., MultipleHypothesis_n)。

   itertools.product()实现的是Cartesian product of input iterables. MultipleHypothesis是一个iterable objects。所以，这个部分输出的结果就是MultipleHypothesis_1、MultipleHypothesis_2,..., MultipleHypothesis_n分别各选出一个hypothesis，然后组合出的所有可能结果。

2.cls.isvalid(joint_hypothesis)

   cls.isvalid()是类的static function method. 它用来检查joint_hypothesis是否合法。itertools.product()输出的joint_hypothesis存在一个量测被同时分配给多个目标的情况，所以要通过cls.isvalid()选出合法的joint_hypothesis。

3. for track, hypothesis in zip(hypotheses, joint_hypothesis)

   zip的第一个参数是一个字典，字典默认是一个iterable object，内容是字典中hypotheses所有的key，也就是对应的目标(航迹）。