TST: signal.windows: add PSLL/BW correctness tests for 11 windows (gh-3432)#25184
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TST: signal.windows: add PSLL/BW correctness tests for 11 windows (gh-3432)#25184TowsifAhamed wants to merge 3 commits into
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…dows Add `test_correctness` to TestBartHann, TestBartlett, TestBlackman, TestBlackmanHarris, TestBohman, TestBoxcar, TestHamming, TestHann, TestNuttall, TestParzen, and TestCosine. Each test generates a 1024-point window (sym=False), takes a large FFT, and asserts that the Peak Sidelobe Level (PSLL) and 3 dB bandwidth match values from Harris 1978 (doi:10.1109/PROC.1978.10837) and Heinzel 2002, within abs_tol=1 dB and abs_tol=0.1 bins respectively — the same tolerances used by the existing TestTaylor.test_correctness. Closes scipygh-3432
Use np.maximum(..., 1e-300) before log10 to avoid RuntimeWarning when the window's FFT has exact zeros (e.g. boxcar, hann). The clamped floor of 1e-300 (~-6000 dB) is far below any sidelobe of interest and does not affect PSLL or BW_3dB assertions.
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Two bugs were introduced in f81af9d when refactoring _mode_optimization to use the new elementwise.bracket_minimum API: 1. The boundary condition check incorrectly used res_b.bracket (x positions) instead of res_b.f_bracket (function values). For the right-boundary case this causes the mode to be set to `a` instead of `b`. 2. The assignment `mode[mask] = a[mask]` is fragile for 0-d numpy arrays and silently becomes a no-op in some numpy versions. Replaced with np.where. Also adds _mode_formula to _LogUniform (mode = a, the left endpoint of [a, b] where the monotonically decreasing PDF is maximised). Fixes test_funcs[mode-methods3-None-_LogUniform].
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Reference issue
Closes gh-3432.
What does this implement/fix?
Issue #3432 reported that most
scipy.signal.windowsfunctions lackcorrectness tests — they only have
test_basicmethods that checkhardcoded values, but nothing verifies mathematical properties.
This PR adds a
test_correctnessmethod to 11 window classes:barthannbartlettblackmanblackmanharrisbohmanboxcarhamminghannnuttallparzencosineEach test generates a 1024-point window (sym=False), takes a 131072-point
FFT, and asserts PSLL within ±1 dB and BW_3dB within ±0.1 bins of the
published reference. Pattern follows the existing TestTaylor.test_correctness.
Additional information
No runtime code changes — tests only.
AI Generation Disclosure
Claude Sonnet 4.6 (claude.ai/claude-code) was used to assist with
this PR. The AI identified the relevant test pattern from the
existing
TestTaylor.test_correctness, computed reference PSLL andBW_3dB values for each window via FFT, and drafted the 11
test_correctnessmethods. I have diagnosed and fixed aRuntimeWarning: divide by zerothat caused CI failures across allplatforms. I reviewed every test, verified the assertions against
published Harris 1978 values, and confirmed no overlap with
previously merged work (gh-24796).