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Increase sampling diversity by RedBlue one-to-one mapping #540

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Increase sampling diversity by RedBlue one-to-one mapping #540

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5c07073
Increase sampling diversity by RedBlue one-to-one mapping
JohannesBuchner Aug 18, 2025
9e9ea81
use indices instead of arrays
JohannesBuchner Aug 18, 2025
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16 changes: 15 additions & 1 deletion src/emcee/moves/stretch.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,4 +30,18 @@ def get_proposal(self, s, c, random):
zz = ((self.a - 1.0) * random.rand(Ns) + 1) ** 2.0 / self.a
factors = (ndim - 1.0) * np.log(zz)
rint = random.randint(Nc, size=(Ns,))
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@dfm dfm Sep 5, 2025

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Perhaps remove this line? It's no longer needed.

return c[rint] - (c[rint] - s) * zz[:, None], factors
# deterministic matching of c to s
# they should be the same size +- 1.
if Nc == Ns:
rint = Ellipsis
elif Nc == Ns + 1: # s is one shorter
rint = slice(0, Ns)
elif Nc == Ns - 1: # s is one longer, reuse one
rint = np.arange(Ns)
# RedBlueMove's permutation means the first element is not special
rint[-1] = 0
else:
# old resampling behaviour; this should not occur
rint = random.randint(Nc, size=(Ns,))
cc = c[rint]
return cc - (cc - s) * zz[:, None], factors