Fix torch-incompatible assertions in TestViewCudaArrayInterfaceGPU (#1999)

* Fix torch-incompatible assertions in TestViewCudaArrayInterfaceGPU

The _check_view method in TestViewCudaArrayInterfaceGPU was missed
during the tensor bridge refactor (#1894) and still used raw numpy
attributes (in_arr.size, in_arr.strides, in_arr.flags, etc.) that
don't work with torch tensors. Use the _arr_* helpers that #1894
added for torch/numpy compatibility.

Caught by the nightly optional-dependency CI (#1987).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Fix strides assertion for torch CAI: allow explicit C-contiguous strides

torch's __cuda_array_interface__ always reports strides, even for
C-contiguous tensors. Use the same assertion pattern as the other
_check_view methods: allow strides to equal the C-contiguous values
instead of requiring None.

Verified locally: 7/7 torch CAI tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Unify strides assertion pattern across all _check_view methods

Use the same if/else pattern with `in (None, strides_in_counts)` in
all three _check_view methods for consistency. Previously TestViewCPU
and TestViewCudaArrayInterfaceGPU used a one-liner that was harder
to read and behaved slightly differently.

Verified locally: 66/66 tests pass across TestViewCPU, TestViewGPU,
and TestViewCudaArrayInterfaceGPU (including all torch variants).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Address review: flip strides assertion, add _arr_dtype, merge main

Per @rwgk's review:
- Flip strides check to branch on view.strides (all 3 _check_view)
- Add _arr_dtype helper using __cuda_array_interface__["typestr"]
  for torch tensors, restore dtype assertion in CAI _check_view
- Merge main to pick up #1998 (numba flags fix)

Verified locally: 76/76 tests pass across all three test classes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: leofang

cuda_core/tests/test_utils.py

@@ -111,6 +111,12 @@ def _arr_is_writeable(arr):
     return arr.flags.writeable if hasattr(arr.flags, "writeable") else True
 
 
+def _arr_dtype(arr):
+    if torch is not None and isinstance(arr, torch.Tensor):
+        return np.dtype(arr.__cuda_array_interface__["typestr"])
+    return arr.dtype
+
+
 def _cpu_array_samples():
     samples = [
         np.empty(3, dtype=np.int32),
@@ -171,7 +177,10 @@ def _check_view(self, view, in_arr):
         assert view.shape == expected_shape
         assert view.size == _arr_size(in_arr)
         strides_in_counts = _arr_strides_in_counts(in_arr)
-        assert (_arr_is_c_contiguous(in_arr) and view.strides is None) or view.strides == strides_in_counts
+        if view.strides is None:
+            assert _arr_is_c_contiguous(in_arr)
+        else:
+            assert view.strides == strides_in_counts
         assert view.device_id == -1
         assert view.is_device_accessible is False
         assert view.exporting_obj is in_arr
@@ -277,8 +286,8 @@ def _check_view(self, view, in_arr, dev):
         assert view.shape == expected_shape
         assert view.size == _arr_size(in_arr)
         strides_in_counts = _arr_strides_in_counts(in_arr)
-        if _arr_is_c_contiguous(in_arr):
-            assert view.strides in (None, strides_in_counts)
+        if view.strides is None:
+            assert _arr_is_c_contiguous(in_arr)
         else:
             assert view.strides == strides_in_counts
         assert view.device_id == dev.device_id
@@ -343,15 +352,16 @@ def test_cuda_array_interface_gpu(self, in_arr, use_stream):
 
     def _check_view(self, view, in_arr, dev):
         assert isinstance(view, StridedMemoryView)
-        assert view.ptr == gpu_array_ptr(in_arr)
-        assert view.shape == in_arr.shape
-        assert view.size == in_arr.size
-        strides_in_counts = convert_strides_to_counts(in_arr.strides, in_arr.dtype.itemsize)
-        if in_arr.flags["C_CONTIGUOUS"]:
-            assert view.strides is None
+        assert view.ptr == _arr_ptr(in_arr)
+        expected_shape = tuple(in_arr.shape)
+        assert view.shape == expected_shape
+        assert view.size == _arr_size(in_arr)
+        strides_in_counts = _arr_strides_in_counts(in_arr)
+        if view.strides is None:
+            assert _arr_is_c_contiguous(in_arr)
         else:
             assert view.strides == strides_in_counts
-        assert view.dtype == in_arr.dtype
+        assert view.dtype == _arr_dtype(in_arr)
         assert view.device_id == dev.device_id
         assert view.is_device_accessible is True
         assert view.exporting_obj is in_arr