Coverage for tests/io/test_prefetch.py: 100%

1"""Tests for asynchronous (prefetching) iteration: EventReader(async_read=True). 

2 

3The iterator must be byte-identical to synchronous iteration, propagate 

4worker exceptions, survive early exits without deadlocking, and guard the 

5reader against concurrent direct reads. 

6""" 

7import numpy as np 

8import pytest 

9 

10from evutils.io import EventReader, EventWriter 

11from evutils.io._prefetch import PrefetchIterator 

12from evutils.types import Event_dtype 

13 

14 

15from typing import Any 

16@pytest.fixture() 

17def raw_file(tmp_path: Any) -> Any: 

18 rng = np.random.default_rng(7) 

19 n = 200_000 

20 ev = np.zeros(n, dtype=Event_dtype) 

21 ev["t"] = np.sort(rng.integers(0, 1_000_000, n)) 

22 ev["x"] = rng.integers(0, 1280, n) 

23 ev["y"] = rng.integers(0, 720, n) 

24 ev["p"] = rng.integers(0, 2, n) 

25 p = tmp_path / "events.raw" 

26 with EventWriter(p) as w: 

27 w.write(ev) 

28 return p, ev 

29 

30 

31@pytest.mark.parametrize("suffix", [".raw", ".npz"]) 

32def test_async_matches_sync(tmp_path: Any, raw_file: Any, suffix: str) -> None: 

33 """Async iteration yields the same windows as sync, for a native (C) 

34 decoder and a pure-Python one.""" 

35 p, ev = raw_file 

36 if suffix == ".npz": 

37 p2 = tmp_path / "events.npz" 

38 with EventWriter(p2) as w: 

39 w.write(ev) 

40 p = p2 

41 

42 with EventReader(p, n_events=30_000) as r: 

43 sync_chunks = [np.asarray(c).copy() for c in r] 

44 with EventReader(p, n_events=30_000, async_read=True) as r: 

45 async_chunks = [np.asarray(c) for c in r] 

46 

47 assert len(sync_chunks) == len(async_chunks) 

48 for s, a in zip(sync_chunks, async_chunks): 

49 assert np.array_equal(s, a) 

50 

51 

52def test_async_ext_triggers(raw_file: Any) -> None: 

53 """(events, triggers) tuples pass through the prefetch queue unchanged.""" 

54 p, _ = raw_file 

55 with EventReader(p, n_events=50_000, ext_trigger=True, async_read=True) as r: 

56 for ev, tr in r: 

57 assert len(ev) > 0 

58 assert hasattr(tr, "id") 

59 

60 

61def test_direct_read_guarded_while_iterating(raw_file: Any) -> None: 

62 p, _ = raw_file 

63 with EventReader(p, n_events=50_000, async_read=True) as r: 

64 it = iter(r) 

65 next(it) 

66 with pytest.raises(RuntimeError, match="asynchronous iterator is active"): 

67 r.read() 

68 with pytest.raises(RuntimeError, match="asynchronous iterator is active"): 

69 r.read_all() 

70 # After exhausting the iterator, direct reads are allowed again. 

71 for _ in it: 

72 pass 

73 assert len(r.read_all()) == 0 # EOF, but no guard error 

74 

75 

76def test_early_break_and_reset(raw_file: Any) -> None: 

77 """Breaking out of async iteration must not deadlock; reset() cancels the 

78 worker and a fresh (async) iteration sees the whole file again.""" 

79 p, ev = raw_file 

80 with EventReader(p, n_events=10_000, async_read=True) as r: 

81 for i, _ in enumerate(r): 

82 if i == 1: 

83 break 

84 r.reset() # cancels the active iterator 

85 total = sum(len(c) for c in r) 

86 assert total == len(ev) 

87 

88 

89def test_close_with_active_iterator(raw_file: Any) -> None: 

90 p, _ = raw_file 

91 r = EventReader(p, n_events=10_000, async_read=True) 

92 it = iter(r) 

93 next(it) 

94 r.close() # must join the worker and not raise 

95 assert r._active_prefetch is None 

96 

97 

98def test_only_one_active_iterator(raw_file: Any) -> None: 

99 p, _ = raw_file 

100 with EventReader(p, n_events=50_000, async_read=True) as r: 

101 it = iter(r) 

102 next(it) 

103 with pytest.raises(RuntimeError, match="asynchronous iterator is active"): 

104 iter(r) 

105 it.close() 

106 r.seek(n=0) 

107 assert sum(len(c) for c in r) > 0 # a new iterator is fine now 

108 

109 

110def test_worker_exception_propagates() -> None: 

111 """An exception raised by the source surfaces in the consumer thread.""" 

112 def broken() -> Any: 

113 yield 1 

114 yield 2 

115 raise ValueError("decoder blew up") 

116 

117 it = PrefetchIterator(broken()) 

118 assert next(it) == 1 

119 assert next(it) == 2 

120 with pytest.raises(ValueError, match="decoder blew up"): 

121 next(it) 

122 

123 

124def test_prefetch_iterator_bounded() -> None: 

125 """The queue never buffers more than `depth` chunks ahead.""" 

126 import time 

127 

128 produced = [] 

129 

130 def source() -> Any: 

131 for i in range(100): 

132 produced.append(i) 

133 yield i 

134 

135 it = PrefetchIterator(source(), depth=2) 

136 time.sleep(0.3) # give the worker every chance to run ahead 

137 # depth chunks buffered + one in the worker's hand at most 

138 assert len(produced) <= 2 + 1 

139 assert list(it) == list(range(100)) 

140 

141 

142def test_prefetch_iterator_close_idempotent() -> None: 

143 it = PrefetchIterator(iter(range(10)), depth=1) 

144 next(it) 

145 it.close() 

146 it.close() 

147 with pytest.raises(StopIteration): 

148 next(it)