Fixed error in arange shape computation

dpt.arange(4, 0, -1) was producing array of wrong size.
Bug fixed, test to be added.

Author: oleksandr-pavlyk

dpctl/tensor/_ctors.py

@@ -454,6 +454,7 @@ def empty(
 
 
 def _coerce_and_infer_dt(*args, dt):
+    "Deduce arange type from sequence spec"
     nd, seq_dt, d = _array_info_sequence(args)
     if d != _host_set or nd != (len(args),):
         raise ValueError("start, stop and step must be Python scalars")
@@ -470,6 +471,24 @@ def _coerce_and_infer_dt(*args, dt):
         raise ValueError(f"Data type {dt} is not supported")
 
 
+def _get_arange_length(start, stop, step):
+    "Compute length of arange sequence"
+    span = stop - start
+    if type(step) in [int, float] and type(span) in [int, float]:
+        offset = -1 if step > 0 else 1
+        tmp = 1 + (span + offset) / step
+        return tmp
+    tmp = span / step
+    if type(tmp) is complex and tmp.imag == 0:
+        tmp = tmp.real
+    else:
+        return tmp
+    k = int(tmp)
+    if k > 0 and float(k) < tmp:
+        tmp = tmp + 1
+    return tmp
+
+
 def arange(
     start,
     /,
@@ -511,9 +530,7 @@ def arange(
         step,
     ), dt = _coerce_and_infer_dt(start, stop, step, dt=dtype)
     try:
-        tmp = 1 + (stop - start - 1) / step
-        if type(tmp) is complex and tmp.imag == 0.0:
-            tmp = tmp.real
+        tmp = _get_arange_length(start, stop, step)
         sh = int(tmp)
         if sh < 0:
             sh = 0
@@ -529,6 +546,7 @@ def arange(
         buffer_ctor_kwargs={"queue": sycl_queue},
     )
     _step = (start + step) - start
+    _step = dt.type(_step)
     hev, _ = ti._linspace_step(start, _step, res, sycl_queue)
     hev.wait()
     return res