Backend paddle: Refactor and add regularizer (#1894)

Author: lijialin03

deepxde/backend/backend.py

@@ -502,3 +502,42 @@ def sparse_dense_matmul(x, y):
     Returns:
         Tensor: The multiplication result.
     """
+
+
+###############################################################################
+# Regularization
+
+
+def l1_regularization(l1):
+    """A regularizer that applies a L1 regularization penalty or L1 weight decay.
+
+    Warning:
+        The implementation may vary across different backends.
+
+    Args:
+        l1 (float): L1 regularization factor. 
+    """
+
+
+def l2_regularization(l2):
+    """A regularizer that applies a L2 regularization penalty or L2 weight decay.
+
+    Warning:
+        The implementation may vary across different backends.
+
+    Args:
+        l2 (float): L2 regularization factor.
+    """
+
+
+def l1_l2_regularization(l1, l2):
+    """A regularizer that applies both L1 and L2 regularization penalties or 
+    L1 and L2 weight decay.
+
+    Warning:
+        The implementation may vary across different backends.
+
+    Args:
+        l1 (float): L1 regularization factor.
+        l2 (float): L2 regularization factor.
+    """

deepxde/backend/paddle/tensor.py

@@ -229,3 +229,11 @@ def matmul(x, y):
 
 def sparse_dense_matmul(x, y):
     return paddle.sparse.matmul(x, y)
+
+
+def l1_regularization(l1):
+    return paddle.regularizer.L1Decay(coeff=l1)
+
+
+def l2_regularization(l2):
+    return paddle.regularizer.L2Decay(coeff=l2)

deepxde/backend/tensorflow/tensor.py

@@ -210,3 +210,15 @@ def zeros_like(input_tensor):
 
 def matmul(x, y):
     return tf.linalg.matmul(x, y)
+
+
+def l1_regularization(l1):
+    return tf.keras.regularizers.L1(l1=l1)
+
+
+def l2_regularization(l2):
+    return tf.keras.regularizers.L2(l2=l2)
+
+
+def l1_l2_regularization(l1, l2):
+    return tf.keras.regularizers.L1L2(l1=l1, l2=l2)

deepxde/backend/tensorflow_compat_v1/tensor.py

@@ -245,3 +245,15 @@ def matmul(x, y):
 
 def sparse_dense_matmul(x, y):
     return tf.sparse.sparse_dense_matmul(x, y)
+
+
+def l1_regularization(l1):
+    return tf.keras.regularizers.L1(l1=l1)
+
+
+def l2_regularization(l2):
+    return tf.keras.regularizers.L2(l2=l2)
+
+
+def l1_l2_regularization(l1, l2):
+    return tf.keras.regularizers.L1L2(l1=l1, l2=l2)

deepxde/nn/regularizers.py

@@ -1,8 +1,8 @@
-from ..backend import tf
+from .. import backend as bkd
 
 
 def get(identifier):
-    """Retrieves a TensorFlow regularizer instance based on the given identifier.
+    """Retrieves a regularizer instance based on the given identifier.
 
     Args:
         identifier (list/tuple): Specifies the type and factor(s) of the regularizer.
@@ -11,7 +11,6 @@ def get(identifier):
             For "l1l2", provide both "l1" and "l2" factors.
     """
 
-    # TODO: other backends
     if identifier is None or not identifier:
         return None
     if not isinstance(identifier, (list, tuple)):
@@ -23,11 +22,12 @@ def get(identifier):
         raise ValueError("Regularization factor must be provided.")
 
     if name == "l1":
-        return tf.keras.regularizers.L1(l1=factor[0])
+        return bkd.l1_regularization(factor[0])
     if name == "l2":
-        return tf.keras.regularizers.L2(l2=factor[0])
+        return bkd.l2_regularization(factor[0])
     if name in ("l1l2", "l1+l2"):
+        # TODO: only supported by 'tensorflow.compat.v1' and 'tensorflow' now.
         if len(factor) < 2:
             raise ValueError("L1L2 regularizer requires both L1/L2 penalties.")
-        return tf.keras.regularizers.L1L2(l1=factor[0], l2=factor[1])
+        return bkd.l1_l2_regularization(factor[0], factor[1])
     raise ValueError(f"Unknown regularizer name: {name}")