fix(utils): preserve explicit zero slice stops

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 - feat: add buffer protocol support to utils by @aisk in #175
+- fix(utils): preserve explicit zero slice stops by @dajiaohuang in #201
 
 ## [0.0.45]
 

ggml/utils.py

@@ -319,7 +319,10 @@ def slice_tensor(
 
     # calculate slice
     start = tuple(idx.start or 0 for idx in indices)
-    end = tuple(idx.stop or get_shape(tensor)[i] for i, idx in enumerate(indices))
+    end = tuple(
+        idx.stop if idx.stop is not None else get_shape(tensor)[i]
+        for i, idx in enumerate(indices)
+    )
     step = tuple(idx.step or 1 for idx in indices)
 
     # get the shape of the slice

tests/test_slice_tensor_empty.py

@@ -0,0 +1,60 @@
+import importlib.util
+import sys
+import types
+from pathlib import Path
+from types import SimpleNamespace
+
+
+def test_slice_tensor_preserves_explicit_zero_stop(monkeypatch):
+    # Exercise the Python wrapper without loading a native ggml shared library.
+    fake_ggml = types.ModuleType("ggml.ggml")
+    type_names = (
+        "F32",
+        "F16",
+        "Q4_0",
+        "Q4_1",
+        "Q5_0",
+        "Q5_1",
+        "Q8_0",
+        "Q8_1",
+        "Q2_K",
+        "Q3_K",
+        "Q4_K",
+        "Q5_K",
+        "Q6_K",
+        "Q8_K",
+        "I8",
+        "I16",
+        "I32",
+        "I64",
+        "F64",
+        "BF16",
+    )
+    for value, name in enumerate(type_names):
+        setattr(fake_ggml, f"GGML_TYPE_{name}", value)
+
+    fake_package = types.ModuleType("ggml")
+    fake_package.__path__ = []
+    fake_package.ggml = fake_ggml
+    monkeypatch.setitem(sys.modules, "ggml", fake_package)
+    monkeypatch.setitem(sys.modules, "ggml.ggml", fake_ggml)
+
+    utils_path = Path(__file__).resolve().parents[1] / "ggml" / "utils.py"
+    spec = importlib.util.spec_from_file_location("ggml_utils_slice_test", utils_path)
+    utils = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(utils)
+
+    tensor = SimpleNamespace(
+        contents=SimpleNamespace(ne=[4, 1, 1, 1], nb=[4, 16, 16, 16])
+    )
+    fake_ggml.ggml_n_dims = lambda _: 1
+    views = []
+
+    def view_1d(_, __, ne0, offset):
+        views.append((ne0, offset))
+        return object()
+
+    fake_ggml.ggml_view_1d = view_1d
+    utils.slice_tensor(None, tensor, [slice(0, 0)])
+
+    assert views == [(0, 0)]