Add CuPy support

Author: dcherian

numpy_groupies/utils_numpy.py

@@ -219,7 +219,7 @@ def _ravel_group_idx(group_idx, a, axis, size, order, method="ravel"):
     size = []
     for ii, s in enumerate(a.shape):
         if method == "ravel":
-            ii_idx = group_idx_in if ii == axis else np.arange(s)
+            ii_idx = group_idx_in if ii == axis else np.arange(s, like=group_idx_in)
             ii_shape = [1] * ndim_a
             ii_shape[ii] = s
             group_idx.append(ii_idx.reshape(ii_shape))
@@ -249,10 +249,8 @@ def offset_labels(group_idx, inshape, axis, order, size):
         group_idx = np.moveaxis(group_idx, axis, -1)
     newshape = group_idx.shape[:-1] + (-1,)
 
-    group_idx = (group_idx +
-                 np.arange(np.prod(newshape[:-1]), dtype=int).reshape(newshape)
-                 * size
-                 )
+    offset_ = np.arange(np.prod(newshape[:-1]), dtype=int, like=group_idx).reshape(newshape)
+    group_idx = group_idx + offset_ * size
     if axis not in (-1, len(inshape) - 1):
         return np.moveaxis(group_idx, -1, axis)
     else: