Remove cross entropy sigmoid loss as deprecated (#496)

* remove loss * fix copyright * add reno
qiskit-community · Nov 14, 2022 · c45a510 · c45a510
1 parent 4b6191d
commit c45a510
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Showing 5 changed files with 6 additions and 39 deletions.
diff --git a/qiskit_machine_learning/algorithms/classifiers/neural_network_classifier.py b/qiskit_machine_learning/algorithms/classifiers/neural_network_classifier.py
@@ -66,7 +66,7 @@ def __init__(
                 function is applied to the index and weighted with the corresponding probability.
             loss: A target loss function to be used in training. Default is `squared_error`,
                 i.e. L2 loss. Can be given either as a string for 'absolute_error' (i.e. L1 Loss),
-                'squared_error', 'cross_entropy', 'cross_entropy_sigmoid', or as a loss function
+                'squared_error', 'cross_entropy', or as a loss function
                 implementing the Loss interface.
             one_hot: Determines in the case of a multi-dimensional result of the
                 neural_network how to interpret the result. If True it is interpreted as a single

diff --git a/qiskit_machine_learning/algorithms/trainable_model.py b/qiskit_machine_learning/algorithms/trainable_model.py
@@ -26,18 +26,15 @@
     L1Loss,
     L2Loss,
     CrossEntropyLoss,
-    CrossEntropySigmoidLoss,
 )
 
 from .objective_functions import ObjectiveFunction
 from .serializable_model import SerializableModelMixin
-from ..deprecation import deprecate_values
 
 
 class TrainableModel(SerializableModelMixin):
     """Base class for ML model that defines a scikit-learn like interface for Estimators."""
 
-    @deprecate_values("0.4.0", {"loss": {"cross_entropy_sigmoid": "<unsupported>"}})
     def __init__(
         self,
         neural_network: NeuralNetwork,
@@ -61,7 +58,7 @@ def __init__(
                 function is applied to the index and weighted with the corresponding probability.
             loss: A target loss function to be used in training. Default is `squared_error`,
                 i.e. L2 loss. Can be given either as a string for 'absolute_error' (i.e. L1 Loss),
-                'squared_error', 'cross_entropy', 'cross_entropy_sigmoid', or as a loss function
+                'squared_error', 'cross_entropy', or as a loss function
                 implementing the Loss interface.
             optimizer: An instance of an optimizer to be used in training. When `None` defaults to SLSQP.
             warm_start: Use weights from previous fit to start next fit.
@@ -87,8 +84,6 @@ def __init__(
                 self._loss = L2Loss()
             elif loss == "cross_entropy":
                 self._loss = CrossEntropyLoss()
-            elif loss == "cross_entropy_sigmoid":
-                self._loss = CrossEntropySigmoidLoss()
             else:
                 raise QiskitMachineLearningError(f"Unknown loss {loss}!")
 

diff --git a/qiskit_machine_learning/utils/loss_functions/__init__.py b/qiskit_machine_learning/utils/loss_functions/__init__.py
@@ -39,7 +39,6 @@
    L1Loss
    L2Loss
    CrossEntropyLoss
-   CrossEntropySigmoidLoss
    SVCLoss
 """
 
@@ -48,7 +47,6 @@
     L1Loss,
     L2Loss,
     CrossEntropyLoss,
-    CrossEntropySigmoidLoss,
 )
 
 from .kernel_loss_functions import KernelLoss, SVCLoss
@@ -59,6 +57,5 @@
     "L1Loss",
     "L2Loss",
     "CrossEntropyLoss",
-    "CrossEntropySigmoidLoss",
     "SVCLoss",
 ]
diff --git a/qiskit_machine_learning/utils/loss_functions/loss_functions.py b/qiskit_machine_learning/utils/loss_functions/loss_functions.py
@@ -16,7 +16,6 @@
 
 import numpy as np
 
-from ...deprecation import warn_deprecated, DeprecatedType
 from ...exceptions import QiskitMachineLearningError
 
 
@@ -176,31 +175,3 @@ def gradient(self, predict: np.ndarray, target: np.ndarray) -> np.ndarray:
         grad = np.einsum("ij,i->ij", predict, np.sum(target, axis=1)) - target
 
         return grad
-
-
-class CrossEntropySigmoidLoss(Loss):
-    """
-    This class computes the cross entropy sigmoid loss and should be used for binary classification.
-    """
-
-    def __init__(self) -> None:
-        warn_deprecated("0.4.0", DeprecatedType.CLASS, "CrossEntropySigmoidLoss")
-        super().__init__()
-
-    def evaluate(self, predict: np.ndarray, target: np.ndarray) -> np.ndarray:
-        self._validate_shapes(predict, target)
-
-        if len(set(target)) != 2:
-            raise QiskitMachineLearningError(
-                "Sigmoid Cross Entropy is used for binary classification!"
-            )
-
-        x = CrossEntropyLoss()
-        return 1.0 / (1.0 + np.exp(-x.evaluate(predict, target)))
-
-    def gradient(self, predict: np.ndarray, target: np.ndarray) -> np.ndarray:
-        self._validate_shapes(predict, target)
-
-        return target * (1.0 / (1.0 + np.exp(-predict)) - 1) + (1 - target) * (
-            1.0 / (1.0 + np.exp(-predict))
-        )
diff --git a/releasenotes/notes/remove-cross-entropy-sigmoid-caa9e794c20e2867.yaml b/releasenotes/notes/remove-cross-entropy-sigmoid-caa9e794c20e2867.yaml
@@ -0,0 +1,4 @@
+---
+deprecations:
+  - |
+    The previously deprecated ``CrossEntropySigmoidLoss`` loss function has been removed.