BUG: lqmn(1,1,0) and lqmn(1,1,0j) return incompatible derivatives #23589
Description
Describe your issue.
I'm also able to repro this with xsf @ f8218da (via xsf-rust). But I thought it might help to report it here for the sake of visibility. Otherwise there's also a dusty "transfer issue" button somewhere around here that might be fun to use.
Reproducing Code Example
>>> import scipy
>>> scipy.__version__
'1.16.1'
>>> scipy.special.lqmn(1, 1, 0)[1]
array([[ 1., 0.],
[ 0., -2.]])
>>> scipy.special.lqmn(1, 1, 0j)[1]
array([[3.13577798e-315+0.j, 0.00000000e+000+0.j],
[0.00000000e+000+0.j, 0.00000000e+000+0.j]])Error message
1 != 0 and -2 != 0SciPy/NumPy/Python version and system information
uv run --with scipy --with pyyaml pythonInstalled 3 packages in 20ms
Python 3.13.7 (main, Aug 18 2025, 19:20:03) [Clang 20.1.4 ] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys, scipy, numpy; print(scipy.__version__, numpy.__version__, sys.version_info); scipy.show_config()
1.16.1 2.3.3 sys.version_info(major=3, minor=13, micro=7, releaselevel='final', serial=0)
Build Dependencies:
blas:
detection method: pkgconfig
found: true
include directory: /opt/_internal/cpython-3.13.5/lib/python3.13/site-packages/scipy_openblas32/include
lib directory: /opt/_internal/cpython-3.13.5/lib/python3.13/site-packages/scipy_openblas32/lib
name: scipy-openblas
openblas configuration: OpenBLAS 0.3.28 DYNAMIC_ARCH NO_AFFINITY Haswell MAX_THREADS=64
pc file directory: /project
version: 0.3.28
lapack:
detection method: pkgconfig
found: true
include directory: /opt/_internal/cpython-3.13.5/lib/python3.13/site-packages/scipy_openblas32/include
lib directory: /opt/_internal/cpython-3.13.5/lib/python3.13/site-packages/scipy_openblas32/lib
name: scipy-openblas
openblas configuration: OpenBLAS 0.3.28 DYNAMIC_ARCH NO_AFFINITY Haswell MAX_THREADS=64
pc file directory: /project
version: 0.3.28
pybind11:
detection method: config-tool
include directory: unknown
name: pybind11
version: 3.0.0
Compilers:
c:
commands: cc
linker: ld.bfd
name: gcc
version: 10.2.1
c++:
commands: c++
linker: ld.bfd
name: gcc
version: 10.2.1
cython:
commands: cython
linker: cython
name: cython
version: 3.1.2
fortran:
commands: gfortran
linker: ld.bfd
name: gcc
version: 10.2.1
pythran:
include directory: ../../tmp/build-env-0fmy4m5d/lib/python3.13/site-packages/pythran
version: 0.18.0
Machine Information:
build:
cpu: x86_64
endian: little
family: x86_64
system: linux
cross-compiled: false
host:
cpu: x86_64
endian: little
family: x86_64
system: linux
Python Information:
path: /tmp/build-env-0fmy4m5d/bin/python
version: '3.13'