From 6626c2c8828206e369775c1fe62a31372d80fff9 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Tue, 7 Jun 2022 16:34:59 -0700
Subject: [PATCH 01/11] Atleast_{1,2,3}d the first implementation

---
 cunumeric/module.py | 47 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index 5b48855f26..6d3603da9f 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -991,6 +991,53 @@ def reshape(a, newshape, order="C"):
     return a.reshape(newshape, order=order)
 
 
+def _reshape_recur(ndim, arr):
+    if arr.ndim < ndim:
+        arr = _reshape_recur(ndim - 1, arr)
+        if ndim == 2:
+            arr = arr.reshape((1,) + arr.shape)
+        else:
+            arr = arr.reshape(arr.shape + (1,))
+
+    return arr
+
+
+def _atleast_nd(ndim, arys):
+    arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
+    inputs = list(arr.view() for arr in arys)
+    result = list(_reshape_recur(ndim, arr) for arr in inputs)
+    # if the number of arrys in `arys` is 1, the return value is a single array
+    if len(result) == 1:
+        result = result[0]
+    """
+    if ndim > 1:
+        arys = atleast_nd(ndim - 1, arys)
+    if ndim == 2:
+        arys = list(
+            arr.reshape((1,) + arr.shape) if arr.ndim < ndim else arr
+            for arr in arys
+        )
+    else:
+        arys = list(
+            arr.reshape(arr.shape + (1,)) if arr.ndim < ndim else arr
+            for arr in arys
+        )
+    """
+    return result
+
+
+def atleast_1d(*arys):
+    return _atleast_nd(1, arys)
+
+
+def atleast_2d(*arys):
+    return _atleast_nd(2, arys)
+
+
+def atleast_3d(*arys):
+    return _atleast_nd(3, arys)
+
+
 # Transpose-like operations
 
 

From b5719f3681fe0041a6b97ee5f08754646227b6f0 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Tue, 14 Jun 2022 16:27:10 -0700
Subject: [PATCH 02/11] Added a test for atleast_nd routines

---
 tests/integration/test_atleast_nd.py | 90 ++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 tests/integration/test_atleast_nd.py

diff --git a/tests/integration/test_atleast_nd.py b/tests/integration/test_atleast_nd.py
new file mode 100644
index 0000000000..3680ddc931
--- /dev/null
+++ b/tests/integration/test_atleast_nd.py
@@ -0,0 +1,90 @@
+# Copyright 2022 NVIDIA Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import numpy as np
+import pytest
+
+import cunumeric as num
+
+
+def _check(a, routine, sizes):
+    b = getattr(np, routine)(*a)
+    c = getattr(num, routine)(*a)
+    is_equal = True
+    err_arr = [b, c]
+
+    if len(b) != len(c):
+        is_equal = False
+        err_arr = [b, c]
+    else:
+        for each in zip(b, c):
+            if not np.array_equal(*each):
+                err_arr = each
+                is_equal = False
+                break
+    print_msg = f"np.{routine}({sizes})"
+    assert is_equal, (
+        f"Failed, {print_msg}\n"
+        f"numpy result: {err_arr[0]}\n"
+        f"cunumeric_result: {err_arr[1]}\n"
+        f"cunumeric and numpy shows"
+        f" different result\n"
+    )
+    print(f"Passed, {print_msg}, np: {b}" f", cunumeric: {c}")
+
+
+DIM = 10
+
+SIZE_CASES = [
+    (0,),  # empty array
+    (1,),  # singlton array
+    (10,),  # scalar
+    (DIM, 1),  # 1D array
+    (DIM, DIM),  # 2D array
+    (DIM, DIM, DIM),  # 3D array
+    (DIM, DIM, DIM, DIM),  # 4D array
+]
+
+
+# test to run atleast_nd w/ a single array
+@pytest.mark.parametrize("size", SIZE_CASES, ids=str)
+def test_atleast_1d(size):
+    a = [np.arange(np.prod(size)).reshape(size)]
+    _check(a, "atleast_1d", size)
+
+
+@pytest.mark.parametrize("size", SIZE_CASES, ids=str)
+def test_atleast_2d(size):
+    a = [np.arange(np.prod(size)).reshape(size)]
+    _check(a, "atleast_2d", size)
+
+
+@pytest.mark.parametrize("size", SIZE_CASES, ids=str)
+def test_atleast_3d(size):
+    a = [np.arange(np.prod(size)).reshape(size)]
+    _check(a, "atleast_3d", size)
+
+
+# test to run atleast_nd w/ list of arrays
+@pytest.mark.parametrize("dim", range(1, 4))
+def test_atleast_nd(dim):
+    a = list(np.arange(np.prod(size)).reshape(size) for size in SIZE_CASES)
+    _check(a, f"atleast_{dim}d", SIZE_CASES)
+
+
+if __name__ == "__main__":
+    import sys
+
+    sys.exit(pytest.main(sys.argv))

From 2e698d8427307071eafc35a8539c70f1767cc2d9 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Tue, 14 Jun 2022 16:28:18 -0700
Subject: [PATCH 03/11] Applied atleast_nd routines to `vstack` and `hstack`

---
 cunumeric/module.py | 35 +++++++----------------------------
 1 file changed, 7 insertions(+), 28 deletions(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index 6d3603da9f..8f274ccd88 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -1002,27 +1002,14 @@ def _reshape_recur(ndim, arr):
     return arr
 
 
-def _atleast_nd(ndim, arys):
-    arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
-    inputs = list(arr.view() for arr in arys)
+def _atleast_nd(ndim, arys, view=True):
+    inputs = arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
+    if view:
+        inputs = list(arr.view() for arr in arys)
     result = list(_reshape_recur(ndim, arr) for arr in inputs)
     # if the number of arrys in `arys` is 1, the return value is a single array
     if len(result) == 1:
         result = result[0]
-    """
-    if ndim > 1:
-        arys = atleast_nd(ndim - 1, arys)
-    if ndim == 2:
-        arys = list(
-            arr.reshape((1,) + arr.shape) if arr.ndim < ndim else arr
-            for arr in arys
-        )
-    else:
-        arys = list(
-            arr.reshape(arr.shape + (1,)) if arr.ndim < ndim else arr
-            for arr in arys
-        )
-    """
     return result
 
 
@@ -1628,10 +1615,7 @@ def vstack(tup):
     """
     # Reshape arrays in the `array_list` if needed before concatenation
     inputs = list(convert_to_cunumeric_ndarray(inp) for inp in tup)
-    reshaped = list(
-        inp.reshape([1, inp.shape[0]]) if inp.ndim == 1 else inp
-        for inp in inputs
-    )
+    reshaped = _atleast_nd(2, inputs, False)
     tup, common_info = check_shape_dtype(reshaped, vstack.__name__, 0)
     common_info.shape = tup[0].shape
 
@@ -1721,14 +1705,9 @@ def dstack(tup):
     Multiple GPUs, Multiple CPUs
     """
     # Reshape arrays to (1,N,1) for ndim ==1 or (M,N,1) for ndim == 2:
-    reshaped = []
+    # reshaped = []
     inputs = list(convert_to_cunumeric_ndarray(inp) for inp in tup)
-    for arr in inputs:
-        if arr.ndim == 1:
-            arr = arr.reshape((1,) + arr.shape + (1,))
-        elif arr.ndim == 2:
-            arr = arr.reshape(arr.shape + (1,))
-        reshaped.append(arr)
+    reshaped = _atleast_nd(3, inputs, False)
     tup, common_info = check_shape_dtype(reshaped, dstack.__name__, 2)
 
     return _concatenate(

From b715a79193e2e6c83e55c3f99c8f3001dff909eb Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Wed, 15 Jun 2022 16:34:53 -0700
Subject: [PATCH 04/11] Added description of atleast_nd routines

---
 cunumeric/module.py | 151 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 115 insertions(+), 36 deletions(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index 8f274ccd88..45f80b3e9e 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -991,40 +991,6 @@ def reshape(a, newshape, order="C"):
     return a.reshape(newshape, order=order)
 
 
-def _reshape_recur(ndim, arr):
-    if arr.ndim < ndim:
-        arr = _reshape_recur(ndim - 1, arr)
-        if ndim == 2:
-            arr = arr.reshape((1,) + arr.shape)
-        else:
-            arr = arr.reshape(arr.shape + (1,))
-
-    return arr
-
-
-def _atleast_nd(ndim, arys, view=True):
-    inputs = arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
-    if view:
-        inputs = list(arr.view() for arr in arys)
-    result = list(_reshape_recur(ndim, arr) for arr in inputs)
-    # if the number of arrys in `arys` is 1, the return value is a single array
-    if len(result) == 1:
-        result = result[0]
-    return result
-
-
-def atleast_1d(*arys):
-    return _atleast_nd(1, arys)
-
-
-def atleast_2d(*arys):
-    return _atleast_nd(2, arys)
-
-
-def atleast_3d(*arys):
-    return _atleast_nd(3, arys)
-
-
 # Transpose-like operations
 
 
@@ -1136,6 +1102,120 @@ def moveaxis(a, source, destination):
 # Changing number of dimensions
 
 
+def _reshape_recur(ndim, arr):
+    if arr.ndim < ndim:
+        arr = _reshape_recur(ndim - 1, arr)
+        if ndim == 2:
+            arr = arr.reshape((1,) + arr.shape)
+        else:
+            arr = arr.reshape(arr.shape + (1,))
+
+    return arr
+
+
+def _atleast_nd(ndim, arys, view=True):
+    inputs = arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
+    if view:
+        inputs = list(arr.view() for arr in arys)
+    result = list(_reshape_recur(ndim, arr) for arr in inputs)
+    # if the number of arrys in `arys` is 1, the return value is a single array
+    if len(result) == 1:
+        result = result[0]
+    return result
+
+
+def atleast_1d(*arys):
+    """
+
+    Convert inputs to arrays with at least one dimension.
+    Scalar inputs are converted to 1-dimensional arrays,
+    whilst higher-dimensional inputs are preserved.
+
+    Parameters
+    ----------
+    arys1, arys2, … : array_like
+        One or more input arrays.
+
+    Returns
+    -------
+    ret : ndarray
+        An array, or list of arrays, each with a.ndim >= 1.
+        Copies are made only if necessary.
+
+    See Also
+    --------
+    numpy.atleast_1d
+
+    Availability
+    --------
+    Multiple GPUs, Multiple CPUs
+    """
+    return _atleast_nd(1, arys)
+
+
+def atleast_2d(*arys):
+    """
+
+    View inputs as arrays with at least two dimensions.
+
+    Parameters
+    ----------
+    arys1, arys2, … : array_like
+        One or more array-like sequences.
+        Non-array inputs are converted to arrays.
+        Arrays that already have two or more dimensions are preserved.
+
+    Returns
+    -------
+    res, res2, … : ndarray
+        An array, or list of arrays, each with a.ndim >= 2.
+        Copies are avoided where possible, and
+        views with two or more dimensions are returned.
+
+    See Also
+    --------
+    numpy.atleast_2d
+
+    Availability
+    --------
+    Multiple GPUs, Multiple CPUs
+    """
+    return _atleast_nd(2, arys)
+
+
+def atleast_3d(*arys):
+    """
+
+    View inputs as arrays with at least three dimensions.
+
+    Parameters
+    ----------
+    arys1, arys2, … : array_like
+        One or more array-like sequences.
+        Non-array inputs are converted to arrays.
+        Arrays that already have two or more dimensions are preserved.
+
+    Returns
+    -------
+    res, res2, … : ndarray
+        An array, or list of arrays, each with a.ndim >= 3.
+        Copies are avoided where possible, and
+        views with three or more dimensions are returned.
+        For example, a 1-D array of shape (N,) becomes
+        a view of shape (1, N, 1),  and a 2-D array of shape (M, N)
+        becomes a view of shape (M, N, 1).
+
+    See Also
+    --------
+    numpy.atleast_3d
+
+    Availability
+    --------
+    Multiple GPUs, Multiple CPUs
+    """
+    return _atleast_nd(3, arys)
+
+
 @add_boilerplate("a")
 def squeeze(a, axis=None):
     """
@@ -1704,9 +1784,8 @@ def dstack(tup):
     --------
     Multiple GPUs, Multiple CPUs
     """
-    # Reshape arrays to (1,N,1) for ndim ==1 or (M,N,1) for ndim == 2:
-    # reshaped = []
     inputs = list(convert_to_cunumeric_ndarray(inp) for inp in tup)
+    # Reshape arrays to (1,N,1) for ndim ==1 or (M,N,1) for ndim == 2:
     reshaped = _atleast_nd(3, inputs, False)
     tup, common_info = check_shape_dtype(reshaped, dstack.__name__, 2)
 

From f67361f8aa19f800482f9daafd882798358d3b58 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Wed, 22 Jun 2022 15:04:52 -0700
Subject: [PATCH 05/11] Modified to do 'reshape' only once for each arr after
 collecting the final shapes of arrays

---
 cunumeric/module.py | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index 45f80b3e9e..9a329375e8 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -1104,20 +1104,25 @@ def moveaxis(a, source, destination):
 
 def _reshape_recur(ndim, arr):
     if arr.ndim < ndim:
-        arr = _reshape_recur(ndim - 1, arr)
+        cur_shape = _reshape_recur(ndim - 1, arr)
         if ndim == 2:
-            arr = arr.reshape((1,) + arr.shape)
+            cur_shape = (1,) + cur_shape
         else:
-            arr = arr.reshape(arr.shape + (1,))
-
-    return arr
+            cur_shape = cur_shape + (1,)
+    else:
+        cur_shape = arr.shape
+    return cur_shape
 
 
 def _atleast_nd(ndim, arys, view=True):
     inputs = arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
     if view:
         inputs = list(arr.view() for arr in arys)
-    result = list(_reshape_recur(ndim, arr) for arr in inputs)
+    result_shapes = list(_reshape_recur(ndim, arr) for arr in inputs)
+    # 'reshape' change the shape of arrays only when arr.shape != shape
+    result = list(
+        arr.reshape(shape) for arr, shape in zip(inputs, result_shapes)
+    )
     # if the number of arrys in `arys` is 1, the return value is a single array
     if len(result) == 1:
         result = result[0]

From 4581e8f6a96a3bf8661f64c34f06cd2653972856 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Wed, 29 Jun 2022 01:22:38 -0700
Subject: [PATCH 06/11] Changed the 'atleast_nd' routines to use type
 annotations and modified 'test_atleast_nd.py' to use LEGATE_MAX_DIM

---
 cunumeric/module.py                  | 20 ++++++++++----------
 tests/integration/test_atleast_nd.py | 10 ++++------
 2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index a7b3025d16..7fb57aa8ae 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -1138,7 +1138,7 @@ def moveaxis(
 # Changing number of dimensions
 
 
-def _reshape_recur(ndim, arr):
+def _reshape_recur(ndim: int, arr: ndarray) -> tuple[int]:
     if arr.ndim < ndim:
         cur_shape = _reshape_recur(ndim - 1, arr)
         if ndim == 2:
@@ -1150,22 +1150,22 @@ def _reshape_recur(ndim, arr):
     return cur_shape
 
 
-def _atleast_nd(ndim, arys, view=True):
+def _atleast_nd(
+    ndim: int, arys: Sequence[ndarray], view: Optional[bool] = True
+) -> Union(list[ndarray], ndarray):
     inputs = arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
     if view:
         inputs = list(arr.view() for arr in arys)
-    result_shapes = list(_reshape_recur(ndim, arr) for arr in inputs)
-    # 'reshape' change the shape of arrays only when arr.shape != shape
-    result = list(
-        arr.reshape(shape) for arr, shape in zip(inputs, result_shapes)
-    )
+    # 'reshape' change the shape of arrays
+    # only when arr.shape != _reshape_recur(ndim,arr)
+    result = list(arr.reshape(_reshape_recur(ndim, arr)) for arr in inputs)
     # if the number of arrys in `arys` is 1, the return value is a single array
     if len(result) == 1:
         result = result[0]
     return result
 
 
-def atleast_1d(*arys):
+def atleast_1d(*arys: Sequence[ndarray]) -> Union(list[ndarray], ndarray):
     """
 
     Convert inputs to arrays with at least one dimension.
@@ -1194,7 +1194,7 @@ def atleast_1d(*arys):
     return _atleast_nd(1, arys)
 
 
-def atleast_2d(*arys):
+def atleast_2d(*arys: Sequence[ndarray]) -> Union(list[ndarray], ndarray):
     """
 
     View inputs as arrays with at least two dimensions.
@@ -1224,7 +1224,7 @@ def atleast_2d(*arys):
     return _atleast_nd(2, arys)
 
 
-def atleast_3d(*arys):
+def atleast_3d(*arys: Sequence[ndarray]) -> Union(list[ndarray], ndarray):
     """
 
     View inputs as arrays with at least three dimensions.
diff --git a/tests/integration/test_atleast_nd.py b/tests/integration/test_atleast_nd.py
index 3680ddc931..67c29f65d6 100644
--- a/tests/integration/test_atleast_nd.py
+++ b/tests/integration/test_atleast_nd.py
@@ -17,6 +17,7 @@
 import pytest
 
 import cunumeric as num
+from legate.core import LEGATE_MAX_DIM
 
 
 def _check(a, routine, sizes):
@@ -47,14 +48,11 @@ def _check(a, routine, sizes):
 
 DIM = 10
 
-SIZE_CASES = [
+SIZE_CASES = list((DIM,) * ndim for ndim in range(LEGATE_MAX_DIM + 1))
+
+SIZE_CASES += [
     (0,),  # empty array
     (1,),  # singlton array
-    (10,),  # scalar
-    (DIM, 1),  # 1D array
-    (DIM, DIM),  # 2D array
-    (DIM, DIM, DIM),  # 3D array
-    (DIM, DIM, DIM, DIM),  # 4D array
 ]
 
 

From fb72962851ab82ef3ff2a97870e13b5c55275308 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Tue, 19 Jul 2022 14:24:10 -0700
Subject: [PATCH 07/11] Made a change with reference to comments on PR
 regarding description of functions

---
 cunumeric/module.py                        | 8 ++++----
 docs/cunumeric/source/api/manipulation.rst | 4 +++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index 7fb57aa8ae..ff0e7f84e9 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -1174,7 +1174,7 @@ def atleast_1d(*arys: Sequence[ndarray]) -> Union(list[ndarray], ndarray):
 
     Parameters
     ----------
-    arys1, arys2, … : array_like
+    *arys : array_like
         One or more input arrays.
 
     Returns
@@ -1201,7 +1201,7 @@ def atleast_2d(*arys: Sequence[ndarray]) -> Union(list[ndarray], ndarray):
 
     Parameters
     ----------
-    arys1, arys2, … : array_like
+    *arys : array_like
         One or more array-like sequences.
         Non-array inputs are converted to arrays.
         Arrays that already have two or more dimensions are preserved.
@@ -1231,10 +1231,10 @@ def atleast_3d(*arys: Sequence[ndarray]) -> Union(list[ndarray], ndarray):
 
     Parameters
     ----------
-    arys1, arys2, … : array_like
+    *arys : array_like
         One or more array-like sequences.
         Non-array inputs are converted to arrays.
-        Arrays that already have two or more dimensions are preserved.
+        Arrays that already have three or more dimensions are preserved.
 
     Returns
     -------
diff --git a/docs/cunumeric/source/api/manipulation.rst b/docs/cunumeric/source/api/manipulation.rst
index c930792050..bed086f10b 100644
--- a/docs/cunumeric/source/api/manipulation.rst
+++ b/docs/cunumeric/source/api/manipulation.rst
@@ -40,7 +40,9 @@ Changing number of dimensions
    :toctree: generated/
 
    squeeze
-
+   atleast_1d
+   atleast_2d
+   atleast_3d
 
 Changing kind of array
 ----------------------

From b071937ba4db3fe24343a9e9dff76f641a624bb6 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Tue, 19 Jul 2022 16:31:05 -0700
Subject: [PATCH 08/11] Made the `view` arugment in `_atleast_nd` not to use
 `Optional`

---
 cunumeric/module.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index ff0e7f84e9..041465a71c 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -1151,7 +1151,7 @@ def _reshape_recur(ndim: int, arr: ndarray) -> tuple[int]:
 
 
 def _atleast_nd(
-    ndim: int, arys: Sequence[ndarray], view: Optional[bool] = True
+    ndim: int, arys: Sequence[ndarray], view: bool = True
 ) -> Union(list[ndarray], ndarray):
     inputs = arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
     if view:

From b32c24b7f7313c325119a53d3b85abe2db3c50eb Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Wed, 20 Jul 2022 15:33:49 -0700
Subject: [PATCH 09/11] Fixed the bug w/ singleton arrays for `vstack` and
 `dstack` after `_atleast_nd` is applied Added a test case for singleton
 arrays in `test_concatenate_stack`

---
 cunumeric/module.py                         | 18 +++++++---------
 tests/integration/test_concatenate_stack.py | 24 ++++++++++++++-------
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index be0ced7992..7e4bc3ffac 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -1153,7 +1153,7 @@ def _reshape_recur(ndim: int, arr: ndarray) -> tuple[int]:
 def _atleast_nd(
     ndim: int, arys: Sequence[ndarray], view: bool = True
 ) -> Union(list[ndarray], ndarray):
-    inputs = arys = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
+    inputs = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
     if view:
         inputs = list(arr.view() for arr in arys)
     # 'reshape' change the shape of arrays
@@ -1714,8 +1714,7 @@ def stack(
             " of input arrays"
         )
 
-    shape = list(common_info.shape)
-    shape.insert(axis, 1)
+    shape = common_info.shape[:axis] + (1,) + common_info.shape[axis:]
     arrays = [arr.reshape(shape) for arr in arrays]
     common_info.shape = tuple(shape)
     return _concatenate(arrays, common_info, axis, out=out)
@@ -1755,11 +1754,10 @@ def vstack(tup: Sequence[ndarray]) -> ndarray:
     Multiple GPUs, Multiple CPUs
     """
     # Reshape arrays in the `array_list` if needed before concatenation
-    inputs = list(convert_to_cunumeric_ndarray(inp) for inp in tup)
-    reshaped = _atleast_nd(2, inputs, False)
+    reshaped = _atleast_nd(2, tup, False)
+    if not isinstance(reshaped, list):
+        reshaped = [reshaped]
     tup, common_info = check_shape_dtype(reshaped, vstack.__name__, 0)
-    common_info.shape = tup[0].shape
-
     return _concatenate(
         tup,
         common_info,
@@ -1845,11 +1843,11 @@ def dstack(tup: Sequence[ndarray]) -> ndarray:
     --------
     Multiple GPUs, Multiple CPUs
     """
-    inputs = list(convert_to_cunumeric_ndarray(inp) for inp in tup)
     # Reshape arrays to (1,N,1) for ndim ==1 or (M,N,1) for ndim == 2:
-    reshaped = _atleast_nd(3, inputs, False)
+    reshaped = _atleast_nd(3, tup, False)
+    if not isinstance(reshaped, list):
+        reshaped = [reshaped]
     tup, common_info = check_shape_dtype(reshaped, dstack.__name__, 2)
-
     return _concatenate(
         tup,
         common_info,
diff --git a/tests/integration/test_concatenate_stack.py b/tests/integration/test_concatenate_stack.py
index 5d3e7be084..6ecc5b45ec 100644
--- a/tests/integration/test_concatenate_stack.py
+++ b/tests/integration/test_concatenate_stack.py
@@ -68,6 +68,8 @@ def run_test(arr, routine, input_size):
 
 DIM = 10
 
+NUM_ARR = [1, 3]
+
 SIZES = [
     (0,),
     (0, 10),
@@ -81,40 +83,46 @@ def run_test(arr, routine, input_size):
 
 
 @pytest.fixture(autouse=True)
-def a(size):
-    return [np.random.randint(low=0, high=100, size=size) for _ in range(3)]
+def a(size, num):
+    return [np.random.randint(low=0, high=100, size=size) for _ in range(num)]
 
 
+@pytest.mark.parametrize("num", NUM_ARR, ids=str)
 @pytest.mark.parametrize("size", SIZES, ids=str)
-def test_concatenate(size, a):
+def test_concatenate(size, num, a):
     run_test(tuple(a), "concatenate", size)
 
 
+@pytest.mark.parametrize("num", NUM_ARR, ids=str)
 @pytest.mark.parametrize("size", SIZES, ids=str)
-def test_stack(size, a):
+def test_stack(size, num, a):
     run_test(tuple(a), "stack", size)
 
 
+@pytest.mark.parametrize("num", NUM_ARR, ids=str)
 @pytest.mark.parametrize("size", SIZES, ids=str)
-def test_hstack(size, a):
+def test_hstack(size, num, a):
     run_test(tuple(a), "hstack", size)
 
 
+@pytest.mark.parametrize("num", NUM_ARR, ids=str)
 @pytest.mark.parametrize("size", SIZES, ids=str)
-def test_column_stack(size, a):
+def test_column_stack(size, num, a):
     run_test(tuple(a), "column_stack", size)
 
 
+@pytest.mark.parametrize("num", NUM_ARR, ids=str)
 @pytest.mark.parametrize("size", SIZES, ids=str)
-def test_column_vstack(size, a):
+def test_vstack(size, num, a):
     # exception for 1d array on vstack
     if len(size) == 2 and size == (1, DIM):
         a.append(np.random.randint(low=0, high=100, size=(DIM,)))
     run_test(tuple(a), "vstack", size)
 
 
+@pytest.mark.parametrize("num", NUM_ARR, ids=str)
 @pytest.mark.parametrize("size", SIZES, ids=str)
-def test_column_dstack(size, a):
+def test_dstack(size, num, a):
     # exception for 1d array on dstack
     if len(size) == 2 and size == (1, DIM):
         a.append(np.random.randint(low=0, high=100, size=(DIM,)))

From 1b87236458080a904e87ba20b1954d904af48091 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Thu, 21 Jul 2022 11:09:40 -0700
Subject: [PATCH 10/11] Minor change for the output format in
 `tests/integration/test_atleast_nd.py`

---
 tests/integration/test_atleast_nd.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/tests/integration/test_atleast_nd.py b/tests/integration/test_atleast_nd.py
index 67c29f65d6..88599ff30d 100644
--- a/tests/integration/test_atleast_nd.py
+++ b/tests/integration/test_atleast_nd.py
@@ -40,8 +40,7 @@ def _check(a, routine, sizes):
         f"Failed, {print_msg}\n"
         f"numpy result: {err_arr[0]}\n"
         f"cunumeric_result: {err_arr[1]}\n"
-        f"cunumeric and numpy shows"
-        f" different result\n"
+        f"cunumeric and numpy shows different result\n"
     )
     print(f"Passed, {print_msg}, np: {b}" f", cunumeric: {c}")
 

From 22f77b855aa855ec8aee4f79bd5e92ef2cd74e55 Mon Sep 17 00:00:00 2001
From: Seonmyeong Bak <sbak@nvidia.com>
Date: Fri, 22 Jul 2022 12:19:33 -0700
Subject: [PATCH 11/11] Delete unnecessary codes regarding `view`

---
 cunumeric/module.py                  | 8 +++-----
 tests/integration/test_atleast_nd.py | 2 +-
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/cunumeric/module.py b/cunumeric/module.py
index 7e4bc3ffac..81a68309ab 100644
--- a/cunumeric/module.py
+++ b/cunumeric/module.py
@@ -1151,11 +1151,9 @@ def _reshape_recur(ndim: int, arr: ndarray) -> tuple[int]:
 
 
 def _atleast_nd(
-    ndim: int, arys: Sequence[ndarray], view: bool = True
+    ndim: int, arys: Sequence[ndarray]
 ) -> Union(list[ndarray], ndarray):
     inputs = list(convert_to_cunumeric_ndarray(arr) for arr in arys)
-    if view:
-        inputs = list(arr.view() for arr in arys)
     # 'reshape' change the shape of arrays
     # only when arr.shape != _reshape_recur(ndim,arr)
     result = list(arr.reshape(_reshape_recur(ndim, arr)) for arr in inputs)
@@ -1754,7 +1752,7 @@ def vstack(tup: Sequence[ndarray]) -> ndarray:
     Multiple GPUs, Multiple CPUs
     """
     # Reshape arrays in the `array_list` if needed before concatenation
-    reshaped = _atleast_nd(2, tup, False)
+    reshaped = _atleast_nd(2, tup)
     if not isinstance(reshaped, list):
         reshaped = [reshaped]
     tup, common_info = check_shape_dtype(reshaped, vstack.__name__, 0)
@@ -1844,7 +1842,7 @@ def dstack(tup: Sequence[ndarray]) -> ndarray:
     Multiple GPUs, Multiple CPUs
     """
     # Reshape arrays to (1,N,1) for ndim ==1 or (M,N,1) for ndim == 2:
-    reshaped = _atleast_nd(3, tup, False)
+    reshaped = _atleast_nd(3, tup)
     if not isinstance(reshaped, list):
         reshaped = [reshaped]
     tup, common_info = check_shape_dtype(reshaped, dstack.__name__, 2)
diff --git a/tests/integration/test_atleast_nd.py b/tests/integration/test_atleast_nd.py
index 88599ff30d..4cc011d637 100644
--- a/tests/integration/test_atleast_nd.py
+++ b/tests/integration/test_atleast_nd.py
@@ -42,7 +42,7 @@ def _check(a, routine, sizes):
         f"cunumeric_result: {err_arr[1]}\n"
         f"cunumeric and numpy shows different result\n"
     )
-    print(f"Passed, {print_msg}, np: {b}" f", cunumeric: {c}")
+    print(f"Passed, {print_msg}, np: {b}, cunumeric: {c}")
 
 
 DIM = 10