Raise error if trying to use Gradients when scope have device or

control dependencies specified(Gradients doesn't currently support them).

tensorflow/go/op/gradients.go

@@ -16,7 +16,12 @@ limitations under the License.
 
 package op
 
-import tf "github.com/tensorflow/tensorflow/tensorflow/go"
+import (
+	"fmt"
+
+	tf "github.com/tensorflow/tensorflow/tensorflow/go"
+)
+
 
 // Gradients adds gradients computation ops to the graph according to scope.
 //
@@ -27,6 +32,15 @@ import tf "github.com/tensorflow/tensorflow/tensorflow/go"
 //
 //  return the partial derivatives
 func Gradients(scope *Scope, y []tf.Output, x []tf.Output, dx ...tf.Output) (output []tf.Output) {
+	if len(scope.controlDependencies) > 0 {
+		scope.UpdateErr("Gradients", fmt.Errorf("Gradients does not currently support control dependencies (via Scope.WithControlDependencies)."))
+		return
+	}
+	if scope.device != "" {
+		scope.UpdateErr("Gradients", fmt.Errorf("Gradients does not currently support device annotations (via Scope.WithDevice)."))
+		return
+	}
+
 	var err error
 	if output, err = scope.graph.AddGradients(scope.opName("Gradients"), y, x, dx); err != nil {
 		scope.UpdateErr("Gradients", err)

tensorflow/go/op/gradients_test.go

@@ -214,3 +214,33 @@ func TestValidateGradientsNames(t *testing.T) {
 		t.Error("Gradients should have failed if executed more than once for scope of the same namespace")
 	}
 }
+
+func TestAddGradientsWithControlDependencies(t *testing.T) {
+	var (
+		s        = NewScope()
+		zero     = Const(s.SubScope("zero"), int32(0))
+		x        = Placeholder(s.SubScope("x"), tf.Float)
+		y0       = Square(s.SubScope("y0"), x)
+		variable = VarHandleOp(s, tf.Int32, tf.ScalarShape())
+		init     = AssignVariableOp(s, variable, zero)
+		readDeps = []*tf.Operation{init}
+	)
+	s = s.WithControlDependencies(readDeps...)
+	Gradients(s, []tf.Output{y0}, []tf.Output{x})
+	if err := s.Err(); err == nil {
+		t.Error("Gradients should have failed when control dependencies are set")
+	}
+}
+
+func TestAddGradientsWithDevice(t *testing.T) {
+	var (
+		s  = NewScope()
+		x  = Placeholder(s.SubScope("x"), tf.Float)
+		y0 = Square(s.SubScope("y0"), x)
+	)
+	s = s.WithDevice("/device:GPU:0")
+	Gradients(s, []tf.Output{y0}, []tf.Output{x})
+	if err := s.Err(); err == nil {
+		t.Error("Gradients should have failed when device is set")
+	}
+}