8000 Preserve stationary probabilities for integer passage-time inputs by antonsoo · Pull Request #263 · pysal/giddy · GitHub
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Preserve stationary probabilities for integer passage-time inputs - #263

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antonsoo:fix/integer-first-passage
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Preserve stationary probabilities for integer passage-time inputs#263
antonsoo wants to merge 1 commit into
pysal:mainfrom
antonsoo:fix/integer-first-passage

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@antonsoo
@antonsoo antonsoo commented Oct 28, 2026
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Integer transition matrices can fail in the public first-passage API:

from giddy.ergodic import mfpt

print(mfpt([[0, 1], [1, 0]]))

Before: LinAlgError: Singular matrix. After: [[2., 1.], [1., 2.]], since a step reaches the other state and two steps return to the starting state.

_mfpt_ergodic stores the fractional stationary distribution in zeros_like(P), truncating it for integer inputs. Boolean inputs also give incorrect results. Build the repeated stationary rows directly with np.tile, as var_mfpt_ergodic already does.

Add integer and boolean cycle regressions with exact passage and return times. Full tests pass on current and CI oldest dependencies. Independent graph traversal and hitting-time equations verify the correction; floating controls, including shipped income-transition analyses, remain exact. The installed wheel and composition with #262 reproduce the results.

@martinfleis
martinfleis commented Oct 28, 2026
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xref pysal/pointpats#216 (comment)

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@antonsoo @martinfleis
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