added dtype argument to stack to set the type of the resulting array explicitly instead of relying on auto-detection, which can be slow

Author: gdementen

doc/source/changes/version_0_30.rst.inc

@@ -224,6 +224,8 @@ Miscellaneous improvements
 
 * added dtype argument to LArray to set the type of the array explicitly instead of relying on auto-detection.
 
+* added dtype argument to stack to set the type of the resulting array explicitly instead of relying on auto-detection.
+
 * implemented :py:obj:`LArray.reverse()` method to reverse one or several axes of an array (closes :issue:`631`).
 
 * added :py:obj:`set_options` allowing to set options for larray within a ``with`` block or globally:

larray/core/array.py

@@ -8268,7 +8268,7 @@ def eye(rows, columns=None, k=0, title=None, dtype=None, meta=None):
 #       ('DE', 'M'): 4, ('DE', 'F'): 5})
 
 
-def stack(elements=None, axis=None, title=None, meta=None, **kwargs):
+def stack(elements=None, axis=None, title=None, meta=None, dtype=None, **kwargs):
     r"""
     Combines several arrays or sessions along an axis.
 
@@ -8288,6 +8288,8 @@ def stack(elements=None, axis=None, title=None, meta=None, **kwargs):
     meta : list of pairs or dict or OrderedDict or Metadata, optional
         Metadata (title, description, author, creation_date, ...) associated with the array.
         Keys must be strings. Values must be of type string, int, float, date, time or datetime.
+    dtype : type, optional
+        Output dtype. Defaults to None (inspect all output values to infer it automatically).
 
     Returns
     -------
@@ -8465,7 +8467,9 @@ def stack(elements=None, axis=None, title=None, meta=None, **kwargs):
                   for v in values]
         result_axes = AxisCollection.union(*[get_axes(v) for v in values])
         result_axes.append(axis)
-        result = empty(result_axes, dtype=common_type(values), meta=meta)
+        if dtype is None:
+            dtype = common_type(values)
+        result = empty(result_axes, dtype=dtype, meta=meta)
         for k, v in zip(axis, values):
             result[k] = v
         return result