logsumexp #18295Description
Describe your issue.
logsumexp loses precision in cases where it shouldn't, and in extreme cases it can return 0 when it should return a nonzero float.
Reproducing Code Example
In [2]: from scipy.special import logsumexp
In [3]: logsumexp([0, -40.0])
Out[3]: 0.0
In [4]: np.logaddexp(0, -40) # This is the expected result of `logsumexp([0, -40.0])`.
Out[4]: 4.248354255291589e-18
SciPy/NumPy/Python version and system information
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"fortran": {
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