8000 If user provides RNG, spawn it before deepcopying (#6948) · scikit-image/scikit-image@f2745cf · GitHub
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stefanvstefanv
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If user provides RNG, spawn it before deepcopying (#6948)
Otherwise, the user can still draw values from the RNG and change its state. See scikit-learn/scikit-learn#16988 (comment)
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‎skimage/feature/brief.py

Lines changed: 14 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -47,7 +47,7 @@ class BRIEF(DescriptorExtractor):
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For matching across images, the same `rng` should be used to construct
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descriptors. To facilitate this:
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(a) `rng` defauls to 1
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(a) `rng` defaults to 1
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(b) Subsequent calls of the ``extract`` method will use the same rng/seed.
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sigma : float, optional
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Standard deviation of the Gaussian low-pass filter applied to the image
@@ -134,10 +134,18 @@ def __init__(self, descriptor_size=256, patch_size=49,
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self.mode = mode
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self.sigma = sigma
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if rng is None:
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self.seed = np.random.SeedSequence()
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if isinstance(rng, np.random.Generator):
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# Spawn an independent RNG from parent RNG provided by the user.
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# This is necessary so that we can safely deepcopy the RNG.
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# See https://github.com/scikit-learn/scikit-learn/issues/16988#issuecomment-1518037853
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bg = rng._bit_generator
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ss = bg._seed_seq
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child_ss, = ss.spawn(1)
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self.rng = np.random.Generator(type(bg)(child_ss))
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elif rng is None:
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self.rng = np.random.default_rng(np.random.SeedSequence())
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else:
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self.seed = rng
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self.rng = np.random.default_rng(rng)
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self.descriptors = None
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self.mask = None
@@ -155,7 +163,8 @@ def extract(self, image, keypoints):
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"""
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check_nD(image, 2)
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rng = np.random.default_rng(copy.deepcopy(self.seed))
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# Copy RNG so we can repeatedly call extract with the same random values
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rng = copy.deepcopy(self.rng)
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image = _prepare_grayscale_input_2D(image)
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‎skimage/feature/tests/test_brief.py

Lines changed: 17 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,6 @@
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import pytest
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import copy
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import numpy as np
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from skimage._shared.testing import assert_array_equal
@@ -80,3 +82,18 @@ def test_border(dtype):
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assert extractor.descriptors.shape[0] == 3
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assert_array_equal(extractor.mask, (False, True, True, True))
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def test_independent_rng():
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img = np.zeros((100, 100), dtype=int)
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keypoints = np.array([[1, 1], [20, 20], [50, 50], [80, 80]])
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rng = np.random.default_rng()
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extractor = BRIEF(patch_size=41, rng=rng)
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x = copy.deepcopy(extractor.rng).random()
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rng.random()
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extractor.extract(img, keypoints)
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z = copy.deepcopy(extractor.rng).random()
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assert x == z

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