BUG: MaskedArray.astype('uint8') with certain fill_value raises warning on ARM (Mac M3) inside Docker (Ubuntu 24.04/25.04) and leads inconsistent output #28403
Description
Describe the issue:
I encountered a warning when converting a MaskedArray to uint8 inside a Docker container running Ubuntu 24.04 or 25.04 on an Apple M3 Mac. The same code runs fine on:
- macOS (outside Docker, on M3)
- Windows WSL2 with Ubuntu 22.04 (both inside and outside Docker)
However, inside Docker (Ubuntu 24.04 or 25.04 on ARM), the following script produces a warning:
import numpy as np
foo = np.ma.masked_equal(np.arange(10, dtype="float32"), 5)
foo.fill_value = -1.0
bar = foo.astype("uint8") # Generates a warning
print(bar.fill_value)
bar.fill_value = 255
print(bar.fill_value)
print(bar.filled().dtype)Note that i found this script on another issue that was caused by another bug and seems solved.
Expected Behavior:
The script should execute without warnings, as it does on other platforms and the output shoud be consistent.
Here is the output that i got from all other platforms.
255
255
uint8Actual Behavior:
A warning is raised when calling astype("uint8") when running in Docker on ARM.
I also noted that print(bar.fill_value) prints 0 only in Docker ARM
/opt/venv/lib/python3.13/site-packages/numpy/ma/core.py:502: RuntimeWarning: invalid value encountered in cast
fill_value = np.asarray(fill_value, dtype=ndtype)
0
255
uint8
2.2.3System information
- Numpy version: 2.2.3
- Docker: Ubuntu 24.04 or 25.04
- Host system: macOS (Apple M3, ARM64)
- np.show_config()
{
"Compilers": {
"c": {
"name": "gcc",
"linker": "ld.bfd",
"version": "10.2.1",
"commands": "cc"
},
"cython": {
"name": "cython",
"linker": "cython",
"version": "3.0.12",
"commands": "cython"
},
"c++": {
"name": "gcc",
"linker": "ld.bfd",
"version": "10.2.1",
"commands": "c++"
}
},
"Machine Information": {
"host": {
"cpu": "aarch64",
"family": "aarch64",
"endian": "little",
"system": "linux"
},
"build": {
"cpu": "aarch64",
"family": "aarch64",
"end
78D7
ian": "little",
"system": "linux"
}
},
"Build Dependencies": {
"blas": {
"name": "scipy-openblas",
"found": true,
"version": "0.3.28",
"detection method": "pkgconfig",
"include directory": "/opt/_internal/cpython-3.13.0/lib/python3.13/site-packages/scipy_openblas64/include",
"lib directory": "/opt/_internal/cpython-3.13.0/lib/python3.13/site-packages/scipy_openblas64/lib",
"openblas configuration": "OpenBLAS 0.3.28 USE64BITINT DYNAMIC_ARCH NO_AFFINITY neoversen1 MAX_THREADS=64",
"pc file directory": "/project/.openblas"
},
"lapack": {
"name": "scipy-openblas",
"found": true,
"version": "0.3.28",
"detection method": "pkgconfig",
"include directory": "/opt/_internal/cpython-3.13.0/lib/python3.13/site-packages/scipy_openblas64/include",
"lib directory": "/opt/_internal/cpython-3.13.0/lib/python3.13/site-packages/scipy_openblas64/lib",
"openblas configuration": "OpenBLAS 0.3.28 USE64BITINT DYNAMIC_ARCH NO_AFFINITY neoversen1 MAX_THREADS=64",
"pc file directory": "/project/.openblas"
}
},
"Python Information": {
"path": "/tmp/build-env-tttxdu3h/bin/python",
"version": "3.13"
},
"SIMD Extensions": {
"baseline": [
"NEON",
"NEON_FP16",
"NEON_VFPV4",
"ASIMD"
],
"found": [
"ASIMDHP",
"ASIMDFHM"
],
"not found": [
"SVE"
]
}
}Additional Notes:
- The issue does not occur on Windows WSL2 (Intel i9 13900) or macOS native (M3).
I also took note of the .whl files:
- WSL2 running Ubuntu 22.04: numpy-2.2.3-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
- WSL2 running Ubuntu 22.04 + Docker running Ubuntu 25.05: numpy-2.2.3-cp313-cp313-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
- macOS native (M3): numpy-2.2.3-cp312-cp312-macosx_14_0_arm64.whl
- macOS + Docker running Ubuntu 25.05: numpy-2.2.3-cp313-cp313-manylinux_2_17_aarch64.manylinux2014_aarch64.whl
Reproduce the code example:
import numpy as np
foo = np.ma.masked_equal(np.arange(10, dtype="float32"), 5)
foo.fill_value = -1.0
bar = foo.astype("uint8") # Generates a warning
print(bar.fill_value)
bar.fill_value = 255
print(bar.fill_value)
print(bar.filled().dtype)Python and NumPy Versions:
3.13.2 (main, Feb 5 2025, 01:23:35) [GCC 14.2.0]
Runtime Environment:
[{
'numpy_version': '2.2.3',
'python': '3.13.2 (main, Feb 5 2025, 01:23:35) [GCC 14.2.0]',
'uname': uname_result(system='Linux', node='4bcdb1f2c3ec', release='6.10.14-linuxkit', version='#1 SMP Fri Nov 29 17:22:03 UTC 2024', machine='aarch64')
},
{'simd_extensions': {'baseline': ['NEON', 'NEON_FP16', 'NEON_VFPV4', 'ASIMD'], 'found': ['ASIMDHP', 'ASIMDFHM'], 'not_found': ['SVE']}},
{
'architecture': 'neoversen1',
'filepath': '/opt/venv/lib/python3.13/site-packages/numpy.libs/libscipy_openblas64_-48fd33d4.so',
'internal_api': 'openblas',
'num_threads': 11,
'prefix': 'libscipy_openblas',
'threading_layer': 'pthreads',
'user_api': 'blas',
'version': '0.3.28'
}]