Describe your issue.

When the shape parameters dfn and dfd of the ncf distribution are both 1.0 or both 2.0, ncf.cdf generates a spurious RuntimeWarning.

Reproducing Code Example

In [87]: import scipy

In [88]: scipy.__version__
Out[88]: '1.10.0.dev0+1953.3644066'

In [89]: from scipy.stats import ncf

In [90]: ncf.cdf(1.5, 2.0, 2.0, 1.0)
/home/warren/repos/git/forks/scipy/build-install/lib/python3.10/site-packages/scipy/stats/_continuous_distns.py:6587: RuntimeWarning: invalid value encountered in _ncf_cdf
  return _boost._ncf_cdf(x, dfn, dfd, nc)
Out[90]: 0.49123845184678905

The value is correct; the only problem is the spurious warning.

SciPy/NumPy/Python version information

1.10.0.dev0+1953.3644066 1.24.0.dev0+809.g852f79700 sys.version_info(major=3, minor=10, micro=1, releaselevel='final', serial=0)