From c17248ad03fb90f9ba75b94fea7b24d3e39221f2 Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Fri, 9 Apr 2021 15:22:34 +0200
Subject: [PATCH 01/12] Added support for tensorflow

---
 modopt/base/backend.py   | 67 ++++++++++++++++++++++++++--------------
 modopt/opt/algorithms.py | 32 ++++---------------
 2 files changed, 50 insertions(+), 49 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index 1f5a7a3a..ecec63b9 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -21,21 +21,39 @@
     import_torch = True
 
 # Handle the compatibility with variable
-gpu_compatibility = {
-    'cupy': False,
-    'cupy-cudnn': False,
+LIBRARIES = {
+    'cupy': None,
+    'tensorflow': None,
+    'numpy': np,
 }
 
 if util.find_spec('cupy') is not None:
     try:
         import cupy as cp
-        gpu_compatibility['cupy'] = True
+        LIBRARIES['cupy'] = cp
+    except ImportError:
+        pass
 
-        if util.find_spec('cupy.cuda.cudnn') is not None:
-            gpu_compatibility['cupy-cudnn'] = True
+if util.find_spec(tensorflow) is not None:
+    try:
+        from tensorflow.experimental.numpy as tnp
+        LIBRARIES['tensorflow'] = tnp
     except ImportError:
         pass
 
+from modopt.interface.errors import warn
+
+def get_backend(backend):
+    if backend not in LIBRARIES.keys() or LIBRARIES[backend] is None:
+        warn(
+            compute_type +
+            ' backend not possible, please ensure that '
+            'the optional libraries are installed. \n'
+            'Reverting to numpy'
+        )
+        backend = 'numpy'
+    return LIBRARIES['backend'], backend
+
 
 def get_array_module(input_data):
     """Get Array Module.
@@ -54,13 +72,17 @@ def get_array_module(input_data):
         The numpy or cupy module
 
     """
-    if gpu_compatibility['cupy']:
-        return cp.get_array_module(input_data)
-
-    return np
+    if LIBRARIES['tensorflow'] is not None:
+        if isinstance(input_data, LIBRARIES['tensorflow'].ndarray):
+            return LIBRARIES['tensorflow']
+    elif LIBRARIES['cupy'] is not None:
+        if isinstance(input_data, LIBRARIES['cupy'].ndarray):
+            return LIBRARIES['cupy']
+    else:
+        return np
 
 
-def move_to_device(input_data):
+def change_backend(input_data, backend='cupy'):
     """Move data to device.
 
     This method moves data from CPU to GPU if we have the
@@ -79,16 +101,11 @@ def move_to_device(input_data):
 
     """
     xp = get_array_module(input_data)
-
-    if xp == cp:
+    txp, target_backend = get_backend(backend)
+    if xp == txp:
         return input_data
-
-    if gpu_compatibility['cupy']:
-        return cp.array(input_data)
-
-    warnings.warn('Cupy is not installed, cannot move data to GPU')
-
-    return input_data
+    else:
+        return txp.array(input_data)
 
 
 def move_to_cpu(input_data):
@@ -110,10 +127,14 @@ def move_to_cpu(input_data):
     """
     xp = get_array_module(input_data)
 
-    if xp == np:
+    if xp == LIBRARIES['numpy']:
         return input_data
-
-    return input_data.get()
+    elif xp == LIBRARIES['cupy']:
+        return input_data.get()
+    elif xp == LIBRARIES['tensorflow']:
+        return input_data.data.numpy()
+    else:
+        raise ValueError('Cant identify the kind of array!')
 
 
 def convert_to_tensor(input_data):
diff --git a/modopt/opt/algorithms.py b/modopt/opt/algorithms.py
index ccd8fe21..66a2258e 100644
--- a/modopt/opt/algorithms.py
+++ b/modopt/opt/algorithms.py
@@ -54,11 +54,6 @@
 from modopt.opt.cost import costObj
 from modopt.opt.linear import Identity
 
-try:
-    import cupy as cp
-except ImportError:  # pragma: no cover
-    pass
-
 
 class SetUp(Observable):
     r"""Algorithm Set-Up.
@@ -92,7 +87,7 @@ def __init__(
         verbose=False,
         progress=True,
         step_size=None,
-        use_gpu=False,
+        compute_backend='numpy',
         **dummy_kwargs,
     ):
 
@@ -123,20 +118,7 @@ def __init__(
             )
             self.add_observer('cv_metrics', observer)
 
-        # Check for GPU
-        if use_gpu:
-            if backend.gpu_compatibility['cupy']:
-                self.xp = cp
-            else:
-                warn(
-                    'CuPy is not installed, cannot run on GPU!'
-                    + 'Running optimization on CPU.',
-                )
-                self.xp = np
-                use_gpu = False
-        else:
-            self.xp = np
-        self.use_gpu = use_gpu
+        self.xp, self.compute_backend = get_backend(compute_backend)
 
     @property
     def metrics(self):
@@ -184,10 +166,7 @@ def copy_data(self, input_data):
             Copy of input data
 
         """
-        if self.use_gpu:
-            return backend.move_to_device(input_data)
-
-        return self.xp.copy(input_data)
+        return self.xp.copy(backend.change_backend(input_data, self.compute_backend))
 
     def _check_input_data(self, input_data):
         """Check input data type.
@@ -205,8 +184,9 @@ def _check_input_data(self, input_data):
             For invalid input type
 
         """
-        if not isinstance(input_data, self.xp.ndarray):
-            raise TypeError('Input data must be a numpy array.')
+        if not isinstance(input_data, self.xp.ndarray) or \
+            not isinstance(input_data, np.ndarray):
+            raise TypeError('Input data must be a numpy array or backend array')
 
     def _check_param(self, param_val):
         """Check algorithm parameters.

From 71ce91c29be58f6649efddabbf3c979edbece45c Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Fri, 9 Apr 2021 16:48:03 +0200
Subject: [PATCH 02/12] Updates to get tests passing

---
 modopt/base/backend.py   | 7 +++----
 modopt/opt/algorithms.py | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index ecec63b9..7c52e1cc 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -34,9 +34,9 @@
     except ImportError:
         pass
 
-if util.find_spec(tensorflow) is not None:
+if util.find_spec('tensorflow') is not None:
     try:
-        from tensorflow.experimental.numpy as tnp
+        import tensorflow.experimental.numpy as tnp
         LIBRARIES['tensorflow'] = tnp
     except ImportError:
         pass
@@ -78,8 +78,7 @@ def get_array_module(input_data):
     elif LIBRARIES['cupy'] is not None:
         if isinstance(input_data, LIBRARIES['cupy'].ndarray):
             return LIBRARIES['cupy']
-    else:
-        return np
+    return np
 
 
 def change_backend(input_data, backend='cupy'):
diff --git a/modopt/opt/algorithms.py b/modopt/opt/algorithms.py
index 66a2258e..c4b7af6f 100644
--- a/modopt/opt/algorithms.py
+++ b/modopt/opt/algorithms.py
@@ -118,7 +118,7 @@ def __init__(
             )
             self.add_observer('cv_metrics', observer)
 
-        self.xp, self.compute_backend = get_backend(compute_backend)
+        self.xp, self.compute_backend = backend.get_backend(compute_backend)
 
     @property
     def metrics(self):

From 990c8219e6849040e60b7a6aca6f688dd22c0b60 Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Mon, 12 Apr 2021 09:36:57 +0200
Subject: [PATCH 03/12] Or --> And

---
 modopt/base/backend.py   | 2 +-
 modopt/opt/algorithms.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index 7c52e1cc..79222e83 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -52,7 +52,7 @@ def get_backend(backend):
             'Reverting to numpy'
         )
         backend = 'numpy'
-    return LIBRARIES['backend'], backend
+    return LIBRARIES[backend], backend
 
 
 def get_array_module(input_data):
diff --git a/modopt/opt/algorithms.py b/modopt/opt/algorithms.py
index c4b7af6f..74fcc2a0 100644
--- a/modopt/opt/algorithms.py
+++ b/modopt/opt/algorithms.py
@@ -184,7 +184,7 @@ def _check_input_data(self, input_data):
             For invalid input type
 
         """
-        if not isinstance(input_data, self.xp.ndarray) or \
+        if not isinstance(input_data, self.xp.ndarray) and \
             not isinstance(input_data, np.ndarray):
             raise TypeError('Input data must be a numpy array or backend array')
 

From 110f453a6b876caa421f065ef4a3ea5982d3346b Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Tue, 13 Apr 2021 15:30:20 +0200
Subject: [PATCH 04/12] Moving modopt to allow working with tensorflow

---
 modopt/base/backend.py   |  5 +++--
 modopt/math/matrix.py    | 14 +++-----------
 modopt/opt/algorithms.py |  8 +++++---
 3 files changed, 11 insertions(+), 16 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index 79222e83..c3ab844c 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -15,6 +15,7 @@
 
 try:
     import torch
+    from torch.utils.dlpack import from_dlpack, to_dlpack
 except ImportError:  # pragma: no cover
     import_torch = False
 else:
@@ -170,7 +171,7 @@ def convert_to_tensor(input_data):
     if xp == np:
         return torch.Tensor(input_data)
 
-    return torch.utils.dlpack.from_dlpack(input_data.toDlpack()).float()
+    return from_dlpack(input_data.toDlpack()).float()
 
 
 def convert_to_cupy_array(input_data):
@@ -202,6 +203,6 @@ def convert_to_cupy_array(input_data):
         )
 
     if input_data.is_cuda:
-        return cp.fromDlpack(torch.utils.dlpack.to_dlpack(input_data))
+        return cp.fromDlpack(to_dlpack(input_data))
 
     return input_data.detach().numpy()
diff --git a/modopt/math/matrix.py b/modopt/math/matrix.py
index cb54cebc..15af171e 100644
--- a/modopt/math/matrix.py
+++ b/modopt/math/matrix.py
@@ -12,12 +12,7 @@
 
 import numpy as np
 
-from modopt.base.backend import get_array_module
-
-try:
-    import cupy as cp
-except ImportError:  # pragma: no cover
-    pass
+from modopt.base.backend import get_array_module, get_backend
 
 
 def gram_schmidt(matrix, return_opt='orthonormal'):
@@ -303,7 +298,7 @@ def __init__(
         data_shape,
         data_type=float,
         auto_run=True,
-        use_gpu=False,
+        compute_backend='numpy',
         verbose=False,
     ):
 
@@ -311,10 +306,7 @@ def __init__(
         self._data_shape = data_shape
         self._data_type = data_type
         self._verbose = verbose
-        if use_gpu:
-            self.xp = cp
-        else:
-            self.xp = np
+        self.xp, self.compute_backend = get_backend(compute_backend)
         if auto_run:
             self.get_spec_rad()
 
diff --git a/modopt/opt/algorithms.py b/modopt/opt/algorithms.py
index 74fcc2a0..55285dd5 100644
--- a/modopt/opt/algorithms.py
+++ b/modopt/opt/algorithms.py
@@ -134,6 +134,8 @@ def metrics(self, metrics):
             raise TypeError(
                 'Metrics must be a dictionary, not {0}.'.format(type(metrics)),
             )
+        else:
+            self._metrics = metrics
 
     def any_convergence_flag(self):
         """Check convergence flag.
@@ -250,7 +252,7 @@ def _check_operator(self, operator):
 
             if not any(parent in tree for parent in self._op_parents):
                 message = '{0} does not inherit an operator parent.'
-                warn(message.format(str(operator.__class__)))
+                #warn(message.format(str(operator.__class__)))
 
     def _compute_metrics(self):
         """Compute metrics during iteration.
@@ -759,8 +761,8 @@ def _update(self):
             self._z_new = self._x_new
 
         # Update old values for next iteration.
-        self.xp.copyto(self._x_old, self._x_new)
-        self.xp.copyto(self._z_old, self._z_new)
+        self._x_old = self.xp.copy(self._x_new)
+        self._z_old = self.xp.copy(self._z_new)
 
         # Update parameter values for next iteration.
         self._update_param()

From bba9db95083930bff46760af770371a8b4ee4d39 Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Tue, 13 Apr 2021 17:37:03 +0200
Subject: [PATCH 05/12] Fix issues with wos

---
 modopt/math/matrix.py    |  4 +++-
 modopt/opt/algorithms.py | 14 ++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/modopt/math/matrix.py b/modopt/math/matrix.py
index 15af171e..be737f52 100644
--- a/modopt/math/matrix.py
+++ b/modopt/math/matrix.py
@@ -306,7 +306,9 @@ def __init__(
         self._data_shape = data_shape
         self._data_type = data_type
         self._verbose = verbose
-        self.xp, self.compute_backend = get_backend(compute_backend)
+        xp, compute_backend = get_backend(compute_backend)
+        self.xp = xp
+        self.compute_backend = compute_backend
         if auto_run:
             self.get_spec_rad()
 
diff --git a/modopt/opt/algorithms.py b/modopt/opt/algorithms.py
index 55285dd5..4bb96999 100644
--- a/modopt/opt/algorithms.py
+++ b/modopt/opt/algorithms.py
@@ -118,7 +118,9 @@ def __init__(
             )
             self.add_observer('cv_metrics', observer)
 
-        self.xp, self.compute_backend = backend.get_backend(compute_backend)
+        xp, compute_backend = backend.get_backend(compute_backend)
+        self.xp = xp
+        self.compute_backend = compute_backend
 
     @property
     def metrics(self):
@@ -168,7 +170,10 @@ def copy_data(self, input_data):
             Copy of input data
 
         """
-        return self.xp.copy(backend.change_backend(input_data, self.compute_backend))
+        return self.xp.copy(backend.change_backend(
+            input_data,
+            self.compute_backend,
+        ))
 
     def _check_input_data(self, input_data):
         """Check input data type.
@@ -188,7 +193,8 @@ def _check_input_data(self, input_data):
         """
         if not isinstance(input_data, self.xp.ndarray) and \
             not isinstance(input_data, np.ndarray):
-            raise TypeError('Input data must be a numpy array or backend array')
+            raise TypeError('Input data must be a numpy array or '
+                            'backend array')
 
     def _check_param(self, param_val):
         """Check algorithm parameters.
@@ -252,7 +258,7 @@ def _check_operator(self, operator):
 
             if not any(parent in tree for parent in self._op_parents):
                 message = '{0} does not inherit an operator parent.'
-                #warn(message.format(str(operator.__class__)))
+                warn(message.format(str(operator.__class__)))
 
     def _compute_metrics(self):
         """Compute metrics during iteration.

From b88c73e37f439e90ec586c9706d78d68f4d2538e Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Tue, 13 Apr 2021 18:27:43 +0200
Subject: [PATCH 06/12] Fix all flakes finally!

---
 modopt/base/backend.py   | 69 ++++++++++++++++++++++++++--------------
 modopt/opt/algorithms.py | 15 +++++----
 2 files changed, 53 insertions(+), 31 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index c3ab844c..aa257be5 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -8,25 +8,29 @@
 
 """
 
-import warnings
+import types
 from importlib import util
 
 import numpy as np
 
+from modopt.interface.errors import warn
+
 try:
     import torch
-    from torch.utils.dlpack import from_dlpack, to_dlpack
+    from torch.utils.dlpack import from_dlpack as torch_from_dlpack
+    from torch.utils.dlpack import to_dlpack as torch_to_dlpack
+
 except ImportError:  # pragma: no cover
     import_torch = False
 else:
     import_torch = True
 
 # Handle the compatibility with variable
-LIBRARIES = {
+LIBRARIES = types.MappingProxyType({
     'cupy': None,
     'tensorflow': None,
     'numpy': np,
-}
+})
 
 if util.find_spec('cupy') is not None:
     try:
@@ -37,21 +41,34 @@
 
 if util.find_spec('tensorflow') is not None:
     try:
-        import tensorflow.experimental.numpy as tnp
+        from tensorflow.experimental import numpy as tnp
         LIBRARIES['tensorflow'] = tnp
     except ImportError:
         pass
 
-from modopt.interface.errors import warn
 
 def get_backend(backend):
+    """Get backend.
+
+    Returns the backend module for input specified by string
+
+    Parameters
+    ----------
+    backend: str
+        String holding the backend name. One of `tensorflow`,
+        `numpy` or `cupy`.
+
+    Returns
+    -------
+    The module for carrying out calculations
+    """
     if backend not in LIBRARIES.keys() or LIBRARIES[backend] is None:
-        warn(
-            compute_type +
-            ' backend not possible, please ensure that '
-            'the optional libraries are installed. \n'
-            'Reverting to numpy'
+        msg = (
+            '{0} backend not possible, please ensure that '
+            + 'the optional libraries are installed.\n'
+            + 'Reverting to numpy'
         )
+        warn(msg.format(backend))
         backend = 'numpy'
     return LIBRARIES[backend], backend
 
@@ -85,34 +102,35 @@ def get_array_module(input_data):
 def change_backend(input_data, backend='cupy'):
     """Move data to device.
 
-    This method moves data from CPU to GPU if we have the
-    compatibility to do so. It returns the same data if
-    it is already on GPU.
+    This method changes the backend of an array
+    This can be used to copy data to GPU or to CPU
 
     Parameters
     ----------
     input_data : numpy.ndarray or cupy.ndarray
         Input data array to be moved
+    backend: str, default `cupy`
+        The backend to use, one among `tensorflow`, `cupy` and
+        `numpy`
 
     Returns
     -------
-    cupy.ndarray
-        The CuPy array residing on GPU
+    backend.ndarray
+        An ndarray of specified backend
 
     """
     xp = get_array_module(input_data)
     txp, target_backend = get_backend(backend)
     if xp == txp:
         return input_data
-    else:
-        return txp.array(input_data)
+    return txp.array(input_data)
 
 
 def move_to_cpu(input_data):
     """Move data to CPU.
 
-    This method moves data from GPU to CPU.It returns the same data if it is
-    already on CPU.
+    This method moves data from GPU to CPU.
+    It returns the same data if it is already on CPU.
 
     Parameters
     ----------
@@ -124,6 +142,10 @@ def move_to_cpu(input_data):
     numpy.ndarray
         The NumPy array residing on CPU
 
+    Raises
+    ------
+    ValueError
+        if the input does not correspond to any array
     """
     xp = get_array_module(input_data)
 
@@ -133,8 +155,7 @@ def move_to_cpu(input_data):
         return input_data.get()
     elif xp == LIBRARIES['tensorflow']:
         return input_data.data.numpy()
-    else:
-        raise ValueError('Cant identify the kind of array!')
+    raise ValueError('Cant identify the kind of array!')
 
 
 def convert_to_tensor(input_data):
@@ -171,7 +192,7 @@ def convert_to_tensor(input_data):
     if xp == np:
         return torch.Tensor(input_data)
 
-    return from_dlpack(input_data.toDlpack()).float()
+    return torch_from_dlpack(input_data.toDlpack()).float()
 
 
 def convert_to_cupy_array(input_data):
@@ -203,6 +224,6 @@ def convert_to_cupy_array(input_data):
         )
 
     if input_data.is_cuda:
-        return cp.fromDlpack(to_dlpack(input_data))
+        return cp.fromDlpack(torch_to_dlpack(input_data))
 
     return input_data.detach().numpy()
diff --git a/modopt/opt/algorithms.py b/modopt/opt/algorithms.py
index 4bb96999..9d80579f 100644
--- a/modopt/opt/algorithms.py
+++ b/modopt/opt/algorithms.py
@@ -132,12 +132,13 @@ def metrics(self, metrics):
 
         if isinstance(metrics, type(None)):
             self._metrics = {}
-        elif not isinstance(metrics, dict):
+            return
+        elif isinstance(metrics, dict):
+            self._metrics = metrics
+        else:
             raise TypeError(
                 'Metrics must be a dictionary, not {0}.'.format(type(metrics)),
             )
-        else:
-            self._metrics = metrics
 
     def any_convergence_flag(self):
         """Check convergence flag.
@@ -191,10 +192,10 @@ def _check_input_data(self, input_data):
             For invalid input type
 
         """
-        if not isinstance(input_data, self.xp.ndarray) and \
-            not isinstance(input_data, np.ndarray):
-            raise TypeError('Input data must be a numpy array or '
-                            'backend array')
+        if not (isinstance(input_data, (self.xp.ndarray, np.ndarray))):
+            raise TypeError(
+                'Input data must be a numpy array or backend array',
+            )
 
     def _check_param(self, param_val):
         """Check algorithm parameters.

From d9c5004447d913ede8556cdf957061460c25b1f2 Mon Sep 17 00:00:00 2001
From: Chaithya G R <chaithyagr@gmail.com>
Date: Wed, 14 Apr 2021 15:50:46 +0200
Subject: [PATCH 07/12] Update modopt/base/backend.py

Co-authored-by: Samuel Farrens <samuel.farrens@gmail.com>
---
 modopt/base/backend.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index aa257be5..77de45cd 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -109,9 +109,9 @@ def change_backend(input_data, backend='cupy'):
     ----------
     input_data : numpy.ndarray or cupy.ndarray
         Input data array to be moved
-    backend: str, default `cupy`
+    backend: str, optional
         The backend to use, one among `tensorflow`, `cupy` and
-        `numpy`
+        `numpy`. Default is `cupy`.
 
     Returns
     -------

From 04feea9d87a8f5a85fc8b6c5c2d27c161ef840c0 Mon Sep 17 00:00:00 2001
From: Chaithya G R <chaithyagr@gmail.com>
Date: Wed, 14 Apr 2021 15:50:52 +0200
Subject: [PATCH 08/12] Update modopt/base/backend.py

Co-authored-by: Samuel Farrens <samuel.farrens@gmail.com>
---
 modopt/base/backend.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index 77de45cd..66a46b15 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -155,7 +155,7 @@ def move_to_cpu(input_data):
         return input_data.get()
     elif xp == LIBRARIES['tensorflow']:
         return input_data.data.numpy()
-    raise ValueError('Cant identify the kind of array!')
+    raise ValueError('Cannot identify the array type.')
 
 
 def convert_to_tensor(input_data):

From c334747c4b09022172c15ecd93d50a5853212a8d Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Wed, 14 Apr 2021 15:52:53 +0200
Subject: [PATCH 09/12] Minute updates to codes

---
 modopt/base/backend.py   | 3 ++-
 modopt/opt/algorithms.py | 1 -
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index 66a46b15..0bc1fe25 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -60,7 +60,8 @@ def get_backend(backend):
 
     Returns
     -------
-    The module for carrying out calculations
+    module
+        The module for carrying out calculations
     """
     if backend not in LIBRARIES.keys() or LIBRARIES[backend] is None:
         msg = (
diff --git a/modopt/opt/algorithms.py b/modopt/opt/algorithms.py
index 9d80579f..fea737cb 100644
--- a/modopt/opt/algorithms.py
+++ b/modopt/opt/algorithms.py
@@ -132,7 +132,6 @@ def metrics(self, metrics):
 
         if isinstance(metrics, type(None)):
             self._metrics = {}
-            return
         elif isinstance(metrics, dict):
             self._metrics = metrics
         else:

From 4e48300abc2665bd6d902fc7fde5016edc24534c Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Wed, 14 Apr 2021 15:55:40 +0200
Subject: [PATCH 10/12] Add dynamic module

---
 modopt/base/backend.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index 0bc1fe25..d1d09f59 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -26,11 +26,11 @@
     import_torch = True
 
 # Handle the compatibility with variable
-LIBRARIES = types.MappingProxyType({
+LIBRARIES = {
     'cupy': None,
     'tensorflow': None,
     'numpy': np,
-})
+}
 
 if util.find_spec('cupy') is not None:
     try:

From cbe8b277ffbdb1ca73bacba0ad95b0c8e8aa0851 Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Wed, 14 Apr 2021 16:03:47 +0200
Subject: [PATCH 11/12] Fix docu

---
 modopt/base/backend.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index d1d09f59..80bf5893 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -60,8 +60,10 @@ def get_backend(backend):
 
     Returns
     -------
-    module
-        The module for carrying out calculations
+    tuple
+        Returns the module for carrying out calculations and the actual backend
+        that was reverted towards. If the right libraries are not installed, the
+        function warns and reverts to `numpy` backend
     """
     if backend not in LIBRARIES.keys() or LIBRARIES[backend] is None:
         msg = (

From 954ee287b517007937f6b78a9bef82410fb5ffb8 Mon Sep 17 00:00:00 2001
From: chaithyagr <chaithyagr@gitlab.com>
Date: Wed, 14 Apr 2021 16:16:32 +0200
Subject: [PATCH 12/12] Fix PEP

---
 modopt/base/backend.py | 5 ++---
 setup.cfg              | 3 ++-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/modopt/base/backend.py b/modopt/base/backend.py
index 80bf5893..def77151 100644
--- a/modopt/base/backend.py
+++ b/modopt/base/backend.py
@@ -8,7 +8,6 @@
 
 """
 
-import types
 from importlib import util
 
 import numpy as np
@@ -62,8 +61,8 @@ def get_backend(backend):
     -------
     tuple
         Returns the module for carrying out calculations and the actual backend
-        that was reverted towards. If the right libraries are not installed, the
-        function warns and reverts to `numpy` backend
+        that was reverted towards. If the right libraries are not installed,
+        the function warns and reverts to `numpy` backend
     """
     if backend not in LIBRARIES.keys() or LIBRARIES[backend] is None:
         msg = (
diff --git a/setup.cfg b/setup.cfg
index 56a40d12..74fb3f79 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -26,7 +26,8 @@ per-file-ignores =
   #Justification: Needed for keeping package version and current API
   *__init__.py*: F401,F403,WPS347,WPS410,WPS412
   #Todo: Rethink conditional imports
-  modopt/base/backend.py: WPS229, WPS420
+  #Todo: How can we bypass mutable constants?
+  modopt/base/backend.py: WPS229, WPS420, WPS407
   #Todo: Rethink conditional imports
   modopt/base/observable.py: WPS420,WPS604
   #Todo: Check string for log formatting