Merge pull request #46 from NREL/gb/minmax

added custom functional layer for basic tensorflow functional layers …

phygnn/layers/custom_layers.py

@@ -785,3 +785,46 @@ def call(self, x, hi_res_feature):
             Output tensor with the hi_res_feature added to x.
         """
         return tf.concat((x, hi_res_feature), axis=-1)
+
+
+class FunctionalLayer(tf.keras.layers.Layer):
+    """Custom layer to implement the tensorflow layer functions (e.g., add,
+    subtract, multiply, maximum, and minimum) with a constant value. These
+    cannot be implemented in phygnn as normal layers because they need to
+    operate on two tensors of equal shape."""
+
+    def __init__(self, name, value):
+        """
+        Parameters
+        ----------
+        name : str
+            Name of the tensorflow layer function to be implemented, options
+            are (all lower-case): add, subtract, multiply, maximum, and minimum
+        value : float
+            Constant value to use in the function operation
+        """
+
+        options = ('add', 'subtract', 'multiply', 'maximum', 'minimum')
+        msg = (f'FunctionalLayer input `name` must be one of "{options}" '
+               f'but received "{name}"')
+        assert name in options, msg
+
+        super().__init__(name=name)
+        self.value = value
+        self.fun = getattr(tf.keras.layers, self.name)
+
+    def call(self, x):
+        """Operates on x with the specified function
+
+        Parameters
+        ----------
+        x : tf.Tensor
+            Input tensor
+
+        Returns
+        -------
+        x : tf.Tensor
+            Output tensor operated on by the specified function
+        """
+        const = tf.constant(value=self.value, shape=x.shape, dtype=x.dtype)
+        return self.fun((x, const))

phygnn/version.py

@@ -1,4 +1,4 @@
 # -*- coding: utf-8 -*-
 """Physics Guided Neural Network version."""
 
-__version__ = '0.0.25'
+__version__ = '0.0.26'

tests/test_layers.py

@@ -12,6 +12,7 @@
     SkipConnection,
     SpatioTemporalExpansion,
     TileLayer,
+    FunctionalLayer,
 )
 from phygnn.layers.handlers import HiddenLayers, Layers
 
@@ -423,3 +424,23 @@ def test_fno_3d():
         x = layer(x)
         with pytest.raises(tf.errors.InvalidArgumentError):
             tf.assert_equal(x_in, x)
+
+
+def test_functional_layer():
+    """Test the generic functional layer"""
+
+    layer = FunctionalLayer('maximum', 1)
+    x = np.random.normal(0.5, 3, size=(1, 4, 4, 6, 3))
+    assert layer(x).numpy().min() == 1.0
+
+    # make sure layer works with input of arbitrary shape
+    x = np.random.normal(0.5, 3, size=(2, 8, 8, 4, 1))
+    assert layer(x).numpy().min() == 1.0
+
+    layer = FunctionalLayer('multiply', 1.5)
+    x = np.random.normal(0.5, 3, size=(1, 4, 4, 6, 3))
+    assert np.allclose(layer(x).numpy(), x * 1.5)
+
+    with pytest.raises(AssertionError) as excinfo:
+        FunctionalLayer('bad_arg', 0)
+    assert "must be one of" in str(excinfo.value)