add DenseUnbiased layer

onn/parametric.py

@@ -62,6 +62,33 @@ class Dense(Layer):
         return dY @ self.coeffs.f.T
 
 
+class DenseUnbiased(Layer):
+    serialized = {
+        'W': 'coeffs',
+    }
+
+    def __init__(self, dim, init=init_he_uniform, reg_w=None):
+        super().__init__()
+        self.dim = int(dim)
+        self.output_shape = (dim,)
+        self.coeffs = self._new_weights('coeffs', init=init,
+                                        regularizer=reg_w)
+
+    def make_shape(self, parent):
+        shape = parent.output_shape
+        self.input_shape = shape
+        assert len(shape) == 1, shape
+        self.coeffs.shape = (shape[0], self.dim)
+
+    def forward(self, X):
+        self.X = X
+        return X @ self.coeffs.f
+
+    def backward(self, dY):
+        self.coeffs.g += self.X.T @ dY
+        return dY @ self.coeffs.f.T
+
+
 # more
 
 class Conv1Dper(Layer):