Add implementation of dpnp.ndarray.view method

Author: antonwolfy

dpnp/dpnp_array.py

@@ -25,6 +25,7 @@
 # *****************************************************************************
 
 import dpctl.tensor as dpt
+import dpctl.tensor._type_utils as dtu
 from dpctl.tensor._numpy_helper import AxisError
 
 import dpnp
@@ -1979,5 +1980,67 @@ def var(
             correction=correction,
         )
 
+    def view(self, dtype=None):
+        """TBD"""
 
-# 'view'
+        old_sh = self.shape
+        old_strides = self.strides
+
+        if dtype is None:
+            return dpnp_array(old_sh, buffer=self, strides=old_strides)
+
+        new_dt = dpnp.dtype(dtype)
+        new_dt = dtu._to_device_supported_dtype(new_dt, self.sycl_device)
+
+        new_itemsz = new_dt.itemsize
+        old_itemsz = self.dtype.itemsize
+        if new_itemsz == old_itemsz:
+            return dpnp_array(
+                old_sh, dtype=new_dt, buffer=self, strides=old_strides
+            )
+
+        ndim = self.ndim
+        if ndim == 0:
+            raise ValueError(
+                "Changing the dtype of a 0d array is only supported "
+                "if the itemsize is unchanged"
+            )
+
+        # resize on last axis only
+        axis = ndim - 1
+        if old_sh[axis] != 1 and self.size != 0 and old_strides[axis] != 1:
+            raise ValueError(
+                "To change to a dtype of a different size, "
+                "the last axis must be contiguous"
+            )
+
+        # normalize strides whenever itemsize changes
+        if old_itemsz > new_itemsz:
+            new_strides = list(
+                el * (old_itemsz // new_itemsz) for el in old_strides
+            )
+        else:
+            new_strides = list(
+                el // (new_itemsz // old_itemsz) for el in old_strides
+            )
+        new_strides[axis] = 1
+        new_strides = tuple(new_strides)
+
+        new_dim = old_sh[axis] * old_itemsz
+        if new_dim % new_itemsz != 0:
+            raise ValueError(
+                "When changing to a larger dtype, its size must be a divisor "
+                "of the total size in bytes of the last axis of the array"
+            )
+
+        # normalize shape whenever itemsize changes
+        new_sh = list(old_sh)
+        new_sh[axis] = new_dim // new_itemsz
+        new_sh = tuple(new_sh)
+
+        return dpnp_array(
+            new_sh,
+            dtype=new_dt,
+            buffer=self,
+            strides=new_strides,
+        )