CI: update minimum Cython version in CI jobs

Also add a comment about `numpy.fft` becoming as fast as `scipy.fft` in 2.0

Co-authored-by: Jarrod Millman <[email protected]>

Author: rgommers

.github/workflows/tests.yml

@@ -18,7 +18,7 @@ jobs:
       CYTHON_TRACE: 1
       CYTHONSPEC: cython
       NUMPY_MIN: numpy==1.23.0
-      CYTHON_MIN: cython==0.29.35
+      CYTHON_MIN: cython==3.0.4
       SCIPY_MIN: scipy==1.9.0
 
     strategy:
@@ -130,7 +130,7 @@ jobs:
       CYTHON_TRACE: 1
       CYTHONSPEC: cython
       NUMPY_MIN: numpy==1.23.0
-      CYTHON_MIN: cython==0.29.35
+      CYTHON_MIN: cython==3.0.4
       SCIPY_MIN: scipy==1.9.0
 
     strategy:

pywt/_cwt.py

@@ -21,6 +21,8 @@
     fftmodule = np.fft
 
     # provide a fallback so scipy is an optional requirement
+    # note: numpy.fft in numpy 2.0 is as fast as scipy.fft, so could be used
+    # unconditionally once the minimum supported numpy version is >=2.0
     def next_fast_len(n):
         """Round up size to the nearest power of two.