Fix getitem

CHANGELOG.md

@@ -50,6 +50,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Fixed `dpctl.lsplatform()` to work correctly when used from within Jupyter notebook [#800](https://github.com/IntelPython/dpctl/pull/800).
 * Fixed script to drive debug build [#835](https://github.com/IntelPython/dpctl/pull/835) and fixed code to compile in debug mode [#836](https://github.com/IntelPython/dpctl/pull/836).
+* Fixed issue with slicing reported in gh-870 in [#871](https://github.com/IntelPython/dpctl/pull/871).
 
 ## [0.12.0] - 03/01/2022
 

dpctl/tensor/_slicing.pxi

@@ -110,6 +110,7 @@ cdef object _basic_slice_meta(object ind, tuple shape,
         new_strides = list()
         k = 0
         new_offset = offset
+        is_empty = False
         for i in range(len(ind)):
             ind_i = ind[i]
             if (ind_i is Ellipsis):
@@ -127,23 +128,27 @@ cdef object _basic_slice_meta(object ind, tuple shape,
                 str_i = (1 if sh_i == 0 else sl_step) * strides[k]
                 new_shape.append(sh_i)
                 new_strides.append(str_i)
-                if sh_i > 0:
+                if sh_i > 0 and not is_empty:
                     new_offset = new_offset + sl_start * strides[k]
+                if sh_i == 0:
+                    is_empty = True
                 k = k_new
             elif is_integral(ind_i):
                 ind_i = ind_i.__index__()
                 if 0 <= ind_i < shape[k]:
                     k_new = k + 1
-                    new_offset = new_offset + ind_i * strides[k]
+                    if not is_empty:
+                        new_offset = new_offset + ind_i * strides[k]
                     k = k_new
                 elif -shape[k] <= ind_i < 0:
                     k_new = k + 1
-                    new_offset = new_offset + (shape[k] + ind_i) * strides[k]
+                    if not is_empty:
+                        new_offset = new_offset + (shape[k] + ind_i) * strides[k]
                     k = k_new
                 else:
                     raise IndexError(
-                        "Index {0} is out of range for "
-                        "axes {1} with size {2}".format(ind_i, k, shape[k]))
+                        ("Index {0} is out of range for "
+                        "axes {1} with size {2}").format(ind_i, k, shape[k]))
         new_shape.extend(shape[k:])
         new_strides.extend(strides[k:])
         return (tuple(new_shape), tuple(new_strides), new_offset)

dpctl/tensor/_usmarray.pyx

@@ -234,10 +234,10 @@ cdef class usm_ndarray:
             else:
                 self._cleanup()
                 raise ValueError(
-                    "buffer='{}' is not understood. "
+                    ("buffer='{}' is not understood. "
                     "Recognized values are 'device', 'shared',  'host', "
                     "an instance of `MemoryUSM*` object, or a usm_ndarray"
-                    "".format(buffer))
+                     "").format(buffer))
         elif isinstance(buffer, usm_ndarray):
             _buffer = buffer.usm_data
         else:
@@ -246,8 +246,8 @@ cdef class usm_ndarray:
         if (_offset + ary_min_displacement < 0 or
            (_offset + ary_max_displacement + 1) * itemsize > _buffer.nbytes):
             self._cleanup()
-            raise ValueError("buffer='{}' can not accomodate the requested "
-                             "array.".format(buffer))
+            raise ValueError(("buffer='{}' can not accomodate "
+                              "the requested array.").format(buffer))
         self.base_ = _buffer
         self.data_ = (<char *> (<size_t> _buffer._pointer)) + itemsize * _offset
         self.shape_ = shape_ptr

dpctl/tests/test_usm_ndarray_ctor.py

@@ -219,6 +219,9 @@ def test_empty_slice():
     assert Y.shape == X.shape
     Z = X[::2]
     assert Z.shape == X.shape
+    X = dpt.empty((0, 4), dtype="u1")
+    assert X[:, 1].shape == (0,)
+    assert X[:, 1:3].shape == (0, 2)
 
 
 def test_slice_constructor_1d():

dpctl/tests/test_usm_ndarray_manipulation.py

@@ -835,6 +835,7 @@ def test_concat_1array(data):
     "data",
     [
         [(1,), (1,), 0],
+        [(0, 2), (0, 2), 1],
         [(0, 2), (2, 2), 0],
         [(2, 1), (2, 2), -1],
         [(2, 2, 2), (2, 1, 2), 1],