Enforce uniqueness of custom prefixes for gradients

7 files changed, 34 insertions, 52 deletions

diff --git a/tensorflow/java/src/main/java/org/tensorflow/Graph.java b/tensorflow/java/src/main/java/org/tensorflow/Graph.java
index 353092701b..32853c1367 100644
--- a/tensorflow/java/src/main/java/org/tensorflow/Graph.java
+++ b/tensorflow/java/src/main/java/org/tensorflow/Graph.java
@@ -152,8 +152,14 @@ public final class Graph implements AutoCloseable {
    * <p>
    * If {@code dx} is null, the implementation will use dx of {@link org.tensorflow.op.core.OnesLike OnesLike} for all
    * shapes in {@code y}.
+   * <p>
+   * {@code prefix} is used as the name prefix applied to all nodes added to the graph to compute gradients. It must
+   * be unique within the provided graph or the operation will fail. 
+   * <p>
+   * If {@code prefix} is null, then the nodes will be added to under the default prefix, which is "gradients" for the 
+   * first invocation, then "gradients_1", "gradients_2", etc. for any subsequent calls to the same graph.
    * 
-   * @param prefix string prefix applied to names of nodes added to the graph to compute gradients.
+   * @param prefix unique string prefix applied before the names of nodes added to the graph to compute gradients.
    *               If null, defaults to "gradients".
    * @param y output of the function to derive
    * @param x inputs of the function for which partial derivatives are computed
diff --git a/tensorflow/java/src/main/java/org/tensorflow/op/NameScope.java b/tensorflow/java/src/main/java/org/tensorflow/op/NameScope.java
index 95a2a2f9f5..2e84cac1ac 100644
--- a/tensorflow/java/src/main/java/org/tensorflow/op/NameScope.java
+++ b/tensorflow/java/src/main/java/org/tensorflow/op/NameScope.java
@@ -56,10 +56,6 @@ final class NameScope {
     String actualName = (opName != null) ? opName : name;
     return fullyQualify(makeUnique(actualName));
   }
-  
-  String opPrefix() {
-    return opPrefix;
-  }
 
   /**
    * Create a new, root-level namescope.
diff --git a/tensorflow/java/src/main/java/org/tensorflow/op/Scope.java b/tensorflow/java/src/main/java/org/tensorflow/op/Scope.java
index cf0b3d98c1..563ea66ef1 100644
--- a/tensorflow/java/src/main/java/org/tensorflow/op/Scope.java
+++ b/tensorflow/java/src/main/java/org/tensorflow/op/Scope.java
@@ -135,17 +135,8 @@ public final class Scope {
    * }</pre>
    *
    * <p><b>Note:</b> if you provide a composite operator building class (i.e, a class that adds a
-   * set of related operations to the graph by calling other operator building code) you should also
-   * create a {@link #withSubScope(String)} scope for the underlying operators to group them under a
-   * meaningful name.
-   *
-   * <pre>{@code
-   * public static Stddev create(Scope scope, ...) {
-   *   // group sub-operations under a common name
-   *   Scope group = scope.withSubScope("stddev");
-   *   ... Sqrt.create(group, Mean.create(group, ...))
-   * }
-   * }</pre>
+   * set of related operations to the graph by calling other operator building code), the provided name 
+   * will act as a subscope to all underlying operators.
    *
    * @param defaultName name for the underlying operator.
    * @return unique name for the operator.
@@ -154,19 +145,6 @@ public final class Scope {
   public String makeOpName(String defaultName) {
     return nameScope.makeOpName(defaultName);
   }
-  
-  /**
-   * The name prefix of this scope.
-   * <p>
-   * This value is the combination of the name of this scope and all of its parents, seperated by a '/', e.g.
-   * <pre>{@code
-   * Scope scope = new Scope(graph);
-   * assertEquals(scope.withSubScope("sub1").withSubScope("sub2").prefix(), "sub1/sub2");
-   * }</pre>
-   */
-  public String prefix() {
-    return nameScope.opPrefix();
-  }
 
   private Scope(Graph graph, NameScope nameScope) {
     this.graph = graph;
diff --git a/tensorflow/java/src/main/java/org/tensorflow/op/core/Gradients.java b/tensorflow/java/src/main/java/org/tensorflow/op/core/Gradients.java
index 6d71ddfff0..5432ff244e 100644
--- a/tensorflow/java/src/main/java/org/tensorflow/op/core/Gradients.java
+++ b/tensorflow/java/src/main/java/org/tensorflow/op/core/Gradients.java
@@ -88,7 +88,11 @@ public class Gradients implements Op, Iterable<Operand<?>> {
         }
       }
     }
-    Output<?>[] dy = scope.graph().addGradients(scope.prefix(), Operands.asOutputs(y), Operands.asOutputs(x), dx);
+    Output<?>[] dy = scope.graph().addGradients(
+        scope.makeOpName("Gradients"), 
+        Operands.asOutputs(y), 
+        Operands.asOutputs(x), 
+        dx);
     return new Gradients(Arrays.asList(dy));
   }
 
diff --git a/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java b/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java
index c02336aebe..56c8f22daa 100644
--- a/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java
+++ b/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java
@@ -239,8 +239,20 @@ public class GraphTest {
       Output<?>[] grad0 = g.addGradients(null, toArray(y0), toArray(x), null);
       assertTrue(grad0[0].op().name().startsWith("gradients/"));
 
-      Output<?>[] grad1 = g.addGradients("more_gradients", toArray(y0), toArray(x), null);
-      assertTrue(grad1[0].op().name().startsWith("more_gradients/"));
+      Output<?>[] grad1 = g.addGradients(null, toArray(y0), toArray(x), null);
+      assertTrue(grad1[0].op().name().startsWith("gradients_1/"));
+
+      Output<?>[] grad2 = g.addGradients("more_gradients", toArray(y0), toArray(x), null);
+      assertTrue(grad2[0].op().name().startsWith("more_gradients/"));
+
+      Output<?>[] grad3 = g.addGradients("even_more_gradients", toArray(y0), toArray(x), null);
+      assertTrue(grad3[0].op().name().startsWith("even_more_gradients/"));
+
+      try {
+        g.addGradients("even_more_gradients", toArray(y0), toArray(x), null);
+      } catch (IllegalArgumentException e) {
+        // expected exception
+      }
     }
   }
   
diff --git a/tensorflow/java/src/test/java/org/tensorflow/op/ScopeTest.java b/tensorflow/java/src/test/java/org/tensorflow/op/ScopeTest.java
index 2fb2c1df48..0e9c7df697 100644
--- a/tensorflow/java/src/test/java/org/tensorflow/op/ScopeTest.java
+++ b/tensorflow/java/src/test/java/org/tensorflow/op/ScopeTest.java
@@ -17,7 +17,6 @@ package org.tensorflow.op;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
 import static org.junit.Assert.fail;
 
 import java.util.HashMap;
@@ -183,20 +182,6 @@ public class ScopeTest {
       assertEquals(21704, result.intValue());
     }
   }
-  
-  @Test
-  public void prefix() {
-    try (Graph g = new Graph()) {
-      Scope s = new Scope(g);
-      assertNull(s.prefix());
-      
-      Scope sub1 = s.withSubScope("sub1");
-      assertEquals("sub1", sub1.prefix());
-
-      Scope sub2 = sub1.withSubScope("sub2");
-      assertEquals("sub1/sub2", sub2.prefix());
-    }
-  }
 
   // "handwritten" sample operator classes
   private static final class Const<T> {
diff --git a/tensorflow/java/src/test/java/org/tensorflow/op/core/GradientsTest.java b/tensorflow/java/src/test/java/org/tensorflow/op/core/GradientsTest.java
index 2ffc69c209..b75f79a421 100644
--- a/tensorflow/java/src/test/java/org/tensorflow/op/core/GradientsTest.java
+++ b/tensorflow/java/src/test/java/org/tensorflow/op/core/GradientsTest.java
@@ -108,17 +108,18 @@ public class GradientsTest {
   }
 
   @Test
-  public void createGradientsWithScopeName() {
+  public void validateGradientsNames() {
     try (Graph g = new Graph()) {
-      Scope scope = new Scope(g);
+      Scope scope = new Scope(g).withSubScope("sub");
 
       Output<Float> x = TestUtil.placeholder(g, "x1", Float.class);
       Output<Float> y = TestUtil.square(g, "y", x);
       
-      Scope gradScope = scope.withSubScope("grads").withSubScope("test");
-      Gradients grads = Gradients.create(gradScope, y, Arrays.asList(x));
+      Gradients grad0 = Gradients.create(scope, y, Arrays.asList(x));
+      assertTrue(grad0.dy(0).op().name().startsWith("sub/Gradients/"));
       
-      assertTrue(grads.dy(0).op().name().startsWith("grads/test/"));
+      Gradients grad1 = Gradients.create(scope.withName("MyGradients"), y, Arrays.asList(x));
+      assertTrue(grad1.dy(0).op().name().startsWith("sub/MyGradients/"));
     }
   }
 }