Fix get_integer_time precision and zero handling

CHANGELOG.md

@@ -32,6 +32,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Fix typo in `ar_model.py` that causes `AttributeError` during evaluation [\#204](https://github.com/mllam/neural-lam/pull/204) @ritinikhil
 
+- Fix `get_integer_time` to avoid floating-point precision issues and correctly handle zero timedelta [#494](https://github.com/mllam/neural-lam/pull/494) @Saptami191
+
 - Changed the hardcoded True to a conditional check "persistent_workers=self.num_workers > 0" [\#235](https://github.com/mllam/neural-lam/pull/235) @santhil-cyber
 
 - Avoid eager download of the MEPS example dataset during pytest collection by lazily initializing it in `tests/conftest.py`, allowing tests to run without triggering a dataset download at import time. [#391](https://github.com/mllam/neural-lam/pull/391) @Saptami191

neural_lam/datastore/npyfilesmeps/compute_standardization_stats.py

@@ -48,7 +48,7 @@ def get_original_indices(self):
         return self.original_indices
 
     def get_original_window_indices(self, step_length):
-        step_int, _ = get_integer_time(step_length.total_seconds())
+        step_int, _ = get_integer_time(step_length)
         return [
             i // step_int for i in range(len(self.original_indices) * step_int)
         ]

neural_lam/utils.py

@@ -601,22 +601,31 @@ def get_integer_time(tdelta) -> tuple[int, str]:
         >>> get_integer_time(timedelta(milliseconds=1000))
         (1, 'seconds')
         >>> get_integer_time(timedelta(days=0.001))
-        (1, 'unknown')
+        (86400, 'milliseconds')
+        >>> get_integer_time(timedelta(0))
+        (0, 'seconds')
     """
-    total_seconds = tdelta.total_seconds()
+    total_microseconds = (
+        tdelta.days * 86400_000000
+        + tdelta.seconds * 1_000000
+        + tdelta.microseconds
+    )
+
+    if total_microseconds == 0:
+        return 0, "seconds"
 
     units = {
-        "weeks": 604800,
-        "days": 86400,
-        "hours": 3600,
-        "minutes": 60,
-        "seconds": 1,
-        "milliseconds": 0.001,
-        "microseconds": 0.000001,
+        "weeks": 604800_000000,
+        "days": 86400_000000,
+        "hours": 3600_000000,
+        "minutes": 60_000000,
+        "seconds": 1_000000,
+        "milliseconds": 1_000,
+        "microseconds": 1,
     }
 
-    for unit, unit_in_seconds in units.items():
-        if total_seconds % unit_in_seconds == 0:
-            return int(total_seconds / unit_in_seconds), unit
+    for unit, unit_us in units.items():
+        if total_microseconds % unit_us == 0:
+            return total_microseconds // unit_us, unit
 
     return 1, "unknown"

tests/test_utils.py

@@ -0,0 +1,29 @@
+# Standard library
+from datetime import timedelta
+
+# First-party
+from neural_lam.utils import get_integer_time
+
+
+def test_days():
+    assert get_integer_time(timedelta(days=14)) == (2, "weeks")
+
+
+def test_hours():
+    assert get_integer_time(timedelta(hours=5)) == (5, "hours")
+
+
+def test_zero():
+    assert get_integer_time(timedelta(0)) == (0, "seconds")
+
+
+def test_milliseconds():
+    assert get_integer_time(timedelta(milliseconds=1000)) == (1, "seconds")
+
+
+def test_negative():
+    assert get_integer_time(timedelta(days=-7)) == (-1, "weeks")
+
+
+def test_float_days():
+    assert get_integer_time(timedelta(days=0.001)) == (86400, "milliseconds")