BUG: Rolling functions doesn't work on decreasing variable index #32385
Description
Code Sample
def test_rolling_on_decreasing_index(self): # GH-19248 index = [ Timestamp("20190101 09:00:00"), Timestamp("20190101 09:00:02"), Timestamp("20190101 09:00:03"), Timestamp("20190101 09:00:05"), Timestamp("20190101 09:00:06"), ] df = DataFrame({"column": [3, 4, 4, 2, 1]}, index=reversed(index)) result = df.rolling("2s").min() expected = DataFrame( {"column": [3.0, 4.0, 4.0, 2.0, 1.0]}, index=reversed(index) ) # actual incorrect output is [3, 3, 3, 2, 1] tm.assert_frame_equal(result, expected)Problem description
Rolling window operations on variable decreasing index don't work even after #28297. The reason for this is that the calculate_variable_window_bounds function doesn't work with decreasing index. Tested with latest master (~version 1.0.1).