Closed as not planned
Description
Describe the bug
Repeatedly the sigmoid activation function produces very similar (multiple dp) outputs for the prediction probabilities, seemingly similar around the average of the predicted value, similar to a linear function. It works when predicting a linear function, but higher order tends to cause issues.
Steps/Code to Reproduce
from sklearn.neural_network import MLPClassifier
import numpy as np
np.random.seed(1)
Data_X = (np.random.random((500,2)))
Data_Y = np.array([int((x[0] + ((2*(x[1]-0.5))**2 - 0.75))>=0) for x in Data_X])
NN = MLPClassifier(hidden_layer_sizes = (20,20),activation = "logistic", random_state = 42)
NN.fit(Data_X,Data_Y)
print(NN.predict(np.array(Data_X[:20])))
print(Data_Y[:20])Expected Results
The prediction does not resemble target data
Actual Results
[1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
[0 0 1 0 0 0 1 0 0 0 1 0 1 1 0 0 1 1 1 0]
Versions
System:
python: 3.13.2 (tags/v3.13.2:4f8bb39, Feb 4 2025, 15:23:48) [MSC v.1942 64 bit (AMD64)]
executable: c:\Users\km\AppData\Local\Programs\Python\Python313\python.exe
machine: Windows-10-10.0.19045-SP0
Python dependencies:
sklearn: 1.6.1
pip: 25.0.1
setuptools: None
numpy: 2.2.3
scipy: 1.15.2
Cython: None
pandas: 2.2.3
matplotlib: 3.10.1
joblib: 1.4.2
threadpoolctl: 3.6.0
Built with OpenMP: True
threadpoolctl info:
user_api: blas
internal_api: openblas
num_threads: 8
prefix: libscipy_openblas
filepath: C:\Users\km\AppData\Local\Programs\Python\Python313\Lib\site-packages\numpy.libs\libscipy_openblas64_-43e11ff0749b8cbe0a615c9cf6737e0e.dll
version: 0.3.28
threading_layer: pthreads
architecture: Haswell
user_api: openmp
internal_api: openmp
num_threads: 8
prefix: vcomp
filepath: C:\Users\km\AppData\Local\Programs\Python\Python313\Lib\site-packages\sklearn\.libs\vcomp140.dll
version: None
user_api: blas
internal_api: openblas
num_threads: 8
prefix: libscipy_openblas
filepath: C:\Users\km\AppData\Local\Programs\Python\Python313\Lib\site-packages\scipy.libs\libscipy_openblas-f07f5a5d207a3a47104dca54d6d0c86a.dll
version: 0.3.28
threading_layer: pthreads
architecture: Haswell