Thanks for your work. But it's a bit strange here in the coreset sampling part

[mengxianghan123]

https://github.com/hcw-00/PatchCore_anomaly_detection/blob/59b67d9f8dd7a7c9e75203ca57e01cedbb1807ba/sampling_methods/kcenter_greedy.py#L104-L120 I think the wanted logic here should be initialing a centre point by random choice (the first if-branch) and all the entire centre points are chosen by argmax the distance (the second if-branch). But for the "self.already_selected" is initialized as an empty list in line 49(not None), so we'll never get into the first if-branch. As for the centre point initializing process, the expression "np.argmax(self.min_distances)" will return 0 for "np.argmax(None)" will return 0. So, as a result, the program selects index-0-feature as algorithm initialization everytime instead of random selecting one as a common practice.

[JefferyChiang]

I agree with your point. I think the first if-branch should be modify into "if not self.already_selected: " for more accurate to the kcenter_greedy algorithm. Have you modify the code and test the difference ?

[mengxianghan123]

Yeah I modifyed the code like the following:

for _ in range(N):
            if not self.already_selected:
                # Initialize centers with a randomly selected datapoint
                ind = np.random.choice(np.arange(self.n_obs))
            else:
                ind = np.argmax(self.min_distances)
           
            assert ind not in self.already_selected

            self.update_distances([ind], only_new=True, reset_dist=False)
            new_batch.append(ind)
            print("Maximum distance from cluster centers is %0.2f" % max(self.min_distances))

            self.already_selected.append(ind)

I didn't test the difference with thorough experiments. I conjectured that there will not be significant difference between the two implementation but our modification is more up to standard and more consistent with the intention of the algorithm

[HoseinHashemi]

This point makes total sense. I also modified the code but haven't thoroughly tested.