Support addition of gradient operations in a graph

8 files changed, 373 insertions, 31 deletions

diff --git a/tensorflow/java/src/main/java/org/tensorflow/Graph.java b/tensorflow/java/src/main/java/org/tensorflow/Graph.java
index d4fd3db5f7..92ab4ef4d7 100644
--- a/tensorflow/java/src/main/java/org/tensorflow/Graph.java
+++ b/tensorflow/java/src/main/java/org/tensorflow/Graph.java
@@ -143,6 +143,68 @@ public final class Graph implements AutoCloseable {
     }
   }
 
+  /**
+   * Adds operations to compute the partial derivatives of sum of {@code y}s w.r.t {@code x}s,
+   * i.e., {@code d(y_1 + y_2 + ...)/dx_1, d(y_1 + y_2 + ...)/dx_2...}
+   * <p> 
+   * {@code dx} are used as initial gradients (which represent the symbolic partial
+   * derivatives of some loss function {@code L} w.r.t. {@code y}).
+   * {@code dx} must be null or have size of {@code y}.
+   * <p>
+   * If {@code dx} is null, the implementation will use dx of {@code OnesLike} for all
+   * shapes in {@code y}.
+   * 
+   * @param y
+   * @param x
+   * @param dx
+   * @return the partial derivatives {@code dy} with the size of {@code x}
+   */
+  public Output<?>[] addGradients(Output<?>[] y, Output<?>[] x, Output<?>[] dx) {
+    final long[] yHandles = new long[y.length];
+    final int[] yIndices = new int[y.length];
+    final long[] xHandles = new long[x.length];
+    final int[] xIndices = new int[x.length];
+    long[] dxHandles = null;
+    int[] dxIndices = null;
+
+    for (int i = 0; i < y.length; ++i) {
+      yHandles[i] = y[i].op().getUnsafeNativeHandle();
+      yIndices[i] = y[i].index();
+    }
+    for (int i = 0; i < x.length; ++i) {
+      xHandles[i] = x[i].op().getUnsafeNativeHandle();
+      xIndices[i] = x[i].index();
+    }
+    if (dx != null && dx.length > 0) {
+      dxHandles = new long[dx.length];
+      dxIndices = new int[dx.length];
+
+      for (int i = 0; i < dx.length; ++i) {
+        dxHandles[i] = dx[i].op().getUnsafeNativeHandle();
+        dxIndices[i] = dx[i].index();
+      }
+    }
+    // Gradient outputs are returned in two continuous arrays concatenated into one. The first holds the native handles 
+    // of the gradient operations while the second holds the index of their output
+    // e.g. given xHandles = [x0Handle, x1Handle, ...] and xIndices = [x0Index, x1Index, ..], we obtain 
+    // dy = [dy0Handle, dy1Handle, ..., dy0Index, dy1Index, ...]
+    long[] dyHandlesAndIndices;
+    synchronized (nativeHandleLock) {
+      dyHandlesAndIndices = addGradients(nativeHandle, yHandles, yIndices, xHandles, xIndices, dxHandles, dxIndices);
+    }
+    int ndy = dyHandlesAndIndices.length >> 1;
+    if (ndy != x.length) {
+      throw new IllegalStateException(String.valueOf(ndy) + " gradients were added to the graph when " + x.length
+          + " were expected");
+    }
+    Output<?>[] dy = new Output<?>[ndy];
+    for (int i = 0, j = ndy; i < ndy; ++i, ++j) {
+      Operation op = new Operation(this, dyHandlesAndIndices[i]);
+      dy[i] = new Output<>(op, (int) dyHandlesAndIndices[j]);
+    }
+    return dy;
+  }
+  
   private final Object nativeHandleLock = new Object();
   private long nativeHandle;
   private int refcount = 0;
@@ -254,6 +316,9 @@ public final class Graph implements AutoCloseable {
 
   private static native byte[] toGraphDef(long handle);
 
+  private static native long[] addGradients(long handle, long[] inputHandles, int[] inputIndices,
+      long[] outputHandles, int[] outputIndices, long[] gradInputHandles, int[] gradInputIndices);
+
   static {
     TensorFlow.init();
   }
diff --git a/tensorflow/java/src/main/java/org/tensorflow/op/training/AddGradients.java b/tensorflow/java/src/main/java/org/tensorflow/op/training/AddGradients.java
new file mode 100644
index 0000000000..2db34bf188
--- /dev/null
+++ b/tensorflow/java/src/main/java/org/tensorflow/op/training/AddGradients.java
@@ -0,0 +1,137 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+package org.tensorflow.op.training;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+
+import org.tensorflow.Operand;
+import org.tensorflow.Output;
+import org.tensorflow.op.Op;
+import org.tensorflow.op.Operands;
+import org.tensorflow.op.Scope;
+import org.tensorflow.op.annotation.Operator;
+
+/**
+ * Adds operations to compute the partial derivatives of sum of {@code y}s w.r.t {@code x}s,
+ * i.e., {@code d(y_1 + y_2 + ...)/dx_1, d(y_1 + y_2 + ...)/dx_2...}
+ * <p> 
+ * If {@code Options.dx()} values are set, they are as the initial symbolic partial derivatives of some loss 
+ * function {@code L} w.r.t. {@code y}. {@code Options.dx()} must have the size of {@code y}.
+ * <p>
+ * If {@code Options.dx()} is not set, the implementation will use dx of {@code OnesLike} for all
+ * shapes in {@code y}.
+ * <p>
+ * The partial derivatives are returned in output {@code dy}, with the size of {@code x}.
+ * <p>
+ * Example of usage:
+ * <pre>{@code
+ * AddGradients gradients = AddGradients.create(scope, Arrays.asList(loss), Arrays.asList(w, b));
+ * 
+ * Constant<Float> alpha = ops.constant(1.0f, Float.class);
+ * ApplyGradientDescent.create(scope, w, alpha, gradients.<Float>dy(0));
+ * ApplyGradientDescent.create(scope, b, alpha, gradients.<Float>dy(1));
+ * }</pre>
+ */
+@Operator
+public class AddGradients implements Op, Iterable<Operand<?>> {
+
+  /**
+   * Optional attributes for {@link AddGradients}
+   */
+  public static class Options {
+    
+    /**
+     * @param dx partial derivatives of some loss function {@code L} w.r.t. {@code y}
+     * @return this option builder
+     */
+    public Options dx(Iterable<Operand<?>> dx) {
+      this.dx = dx;
+      return this;
+    }
+    
+    private Iterable<Operand<?>> dx;
+    
+    private Options() {
+    }
+  }
+
+  /**
+   * Adds gradients computation ops to the graph according to scope.
+   * 
+   * @param scope current graph scope
+   * @param y 
+   * @param x
+   * @param dx
+   * @return a new instance of {@code AddGradients}
+   */
+  public static AddGradients create(Scope scope, Iterable<Operand<?>> y, Iterable<Operand<?>> x, Options... options) {
+    Output<?>[] dx = null;
+    if (options != null) {
+      for (Options opts : options) {
+        if (opts.dx != null) {
+          dx = Operands.asOutputs(opts.dx);
+        }
+      }
+    }
+    Output<?>[] gradOutputs = scope.graph().addGradients(Operands.asOutputs(y), Operands.asOutputs(x), dx);
+    return new AddGradients(Arrays.asList(gradOutputs));
+  }
+
+  /**
+   * @param dx partial derivatives of some loss function {@code L} w.r.t. {@code y}
+   * @return builder to add more options to this operation
+   */
+  public Options dx(Iterable<Operand<?>> dx) {
+    return new Options().dx(dx);
+  }
+
+  @Override
+  @SuppressWarnings({"rawtypes", "unchecked"})
+  public Iterator<Operand<?>> iterator() {
+    return (Iterator) dy.iterator();
+  }
+  
+  /**
+   * {@code dy} of size {@code x}, i.e. the outputs of the operations added to the graph to compute gradients for each
+   * {@code x} nodes respectively.
+   */
+  public List<Output<?>> dy() {
+    return dy;
+  }
+  
+  /**
+   * Returns a symbolic handle to one of the gradient operation output
+   * <p>
+   * Warning: Does not check that the type of the tensor matches T. It is recommended to call
+   * this method with an explicit type parameter rather than letting it be inferred, e.g. {@code
+   * gradients.<Integer>dy(0)}
+   *
+   * @param <T> The expected element type of the tensors produced by this output.
+   * @param index The index of the output among the gradients added by this operation
+   */
+  @SuppressWarnings("unchecked")
+  public <T> Output<T> dy(int index) {
+    return (Output<T>) dy.get(index);
+  }
+
+  private List<Output<?>> dy;
+  
+  private AddGradients(List<Output<?>> dy) {
+    this.dy = dy;
+  }
+}
diff --git a/tensorflow/java/src/main/native/graph_jni.cc b/tensorflow/java/src/main/native/graph_jni.cc
index 0fef155275..dac6a345e9 100644
--- a/tensorflow/java/src/main/native/graph_jni.cc
+++ b/tensorflow/java/src/main/native/graph_jni.cc
@@ -16,7 +16,9 @@ limitations under the License.
 #include "tensorflow/java/src/main/native/graph_jni.h"
 
 #include <limits>
+#include <memory>
 #include "tensorflow/c/c_api.h"
+#include "tensorflow/java/src/main/native/utils_jni.h"
 #include "tensorflow/java/src/main/native/exception_jni.h"
 
 namespace {
@@ -130,3 +132,55 @@ Java_org_tensorflow_Graph_toGraphDef(JNIEnv* env, jclass clazz, jlong handle) {
   TF_DeleteBuffer(buf);
   return ret;
 }
+
+JNIEXPORT jlongArray JNICALL
+Java_org_tensorflow_Graph_addGradients(JNIEnv* env, jclass clazz, jlong handle,
+    jlongArray y_handles, jintArray y_indices,
+    jlongArray x_handles, jintArray x_indices,
+    jlongArray dx_handles, jintArray dx_indices) {
+
+  TF_Graph* g = requireHandle(env, handle);
+  if (g == nullptr) return nullptr;
+
+  const jint ny = env->GetArrayLength(y_handles);
+  const jint nx = env->GetArrayLength(x_handles);
+
+  std::unique_ptr<TF_Output[]> y(new TF_Output[ny]);
+  std::unique_ptr<TF_Output[]> x(new TF_Output[nx]);
+  std::unique_ptr<TF_Output[]> dx(nullptr);
+  std::unique_ptr<TF_Output[]> dy(new TF_Output[nx]);
+
+  resolveOutputs(env, "y", y_handles, y_indices, y.get(), ny);
+  resolveOutputs(env, "x", x_handles, x_indices, x.get(), nx);
+  if (dx_handles != nullptr) {
+    if (env->GetArrayLength(dx_handles) != ny) {
+      throwException(env, kIllegalArgumentException,
+                     "expected %d, got %d dx handles", ny,
+                     env->GetArrayLength(dx_handles));
+    }
+    dx.reset(new TF_Output[ny]);
+    resolveOutputs(env, "dx", dx_handles, dx_indices, dx.get(), ny);
+  }
+  if (env->ExceptionCheck()) return nullptr;
+
+  TF_Status* status = TF_NewStatus();
+  TF_AddGradients(g, y.get(), ny, x.get(), nx, dx.get(), status, dy.get());
+
+  if (!throwExceptionIfNotOK(env, status)) {
+    TF_DeleteStatus(status);
+    return nullptr;
+  }
+  TF_DeleteStatus(status);
+
+  // returned array contains both op handles and output indices, in pair
+  jlongArray dy_handles_and_indices = env->NewLongArray(nx << 1);
+  jlong* dy_elems = env->GetLongArrayElements(dy_handles_and_indices, nullptr);
+  for (int i = 0, j = nx; i < nx; ++i, ++j) {
+    TF_Output dy_output = dy.get()[i];
+    dy_elems[i] = reinterpret_cast<jlong>(dy_output.oper);
+    dy_elems[j] = static_cast<jlong>(dy_output.index);
+  }
+  env->ReleaseLongArrayElements(dy_handles_and_indices, dy_elems, 0);
+
+  return dy_handles_and_indices;
+}
diff --git a/tensorflow/java/src/main/native/graph_jni.h b/tensorflow/java/src/main/native/graph_jni.h
index dd2e038332..4f87e8d5a7 100644
--- a/tensorflow/java/src/main/native/graph_jni.h
+++ b/tensorflow/java/src/main/native/graph_jni.h
@@ -73,6 +73,15 @@ JNIEXPORT jbyteArray JNICALL Java_org_tensorflow_Graph_toGraphDef(JNIEnv *,
                                                                   jclass,
                                                                   jlong);
 
+/*
+ * Class:     org_tensorflow_Graph
+ * Method:    name
+ * Signature: (J[J[I[J[I[J[I)[J
+ */
+JNIEXPORT jlongArray JNICALL Java_org_tensorflow_Graph_addGradients(JNIEnv *,
+    jclass, jlong, jlongArray, jintArray, jlongArray, jintArray, jlongArray,
+    jintArray);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus
diff --git a/tensorflow/java/src/main/native/session_jni.cc b/tensorflow/java/src/main/native/session_jni.cc
index 2cd542d3c9..cb54daf137 100644
--- a/tensorflow/java/src/main/native/session_jni.cc
+++ b/tensorflow/java/src/main/native/session_jni.cc
@@ -17,6 +17,7 @@ limitations under the License.
 #include <memory>
 
 #include "tensorflow/c/c_api.h"
+#include "tensorflow/java/src/main/native/utils_jni.h"
 #include "tensorflow/java/src/main/native/exception_jni.h"
 #include "tensorflow/java/src/main/native/session_jni.h"
 
@@ -55,37 +56,6 @@ void resolveHandles(JNIEnv* env, const char* type, jlongArray src_array,
   env->ReleaseLongArrayElements(src_array, src_start, JNI_ABORT);
 }
 
-void resolveOutputs(JNIEnv* env, const char* type, jlongArray src_op,
-                    jintArray src_index, TF_Output* dst, jint n) {
-  if (env->ExceptionCheck()) return;
-  jint len = env->GetArrayLength(src_op);
-  if (len != n) {
-    throwException(env, kIllegalArgumentException,
-                   "expected %d, got %d %s Operations", n, len, type);
-    return;
-  }
-  len = env->GetArrayLength(src_index);
-  if (len != n) {
-    throwException(env, kIllegalArgumentException,
-                   "expected %d, got %d %s Operation output indices", n, len,
-                   type);
-    return;
-  }
-  jlong* op_handles = env->GetLongArrayElements(src_op, nullptr);
-  jint* indices = env->GetIntArrayElements(src_index, nullptr);
-  for (int i = 0; i < n; ++i) {
-    if (op_handles[i] == 0) {
-      throwException(env, kNullPointerException, "invalid %s (#%d of %d)", type,
-                     i, n);
-      break;
-    }
-    dst[i] = TF_Output{reinterpret_cast<TF_Operation*>(op_handles[i]),
-                       static_cast<int>(indices[i])};
-  }
-  env->ReleaseIntArrayElements(src_index, indices, JNI_ABORT);
-  env->ReleaseLongArrayElements(src_op, op_handles, JNI_ABORT);
-}
-
 void TF_MaybeDeleteBuffer(TF_Buffer* buf) {
   if (buf == nullptr) return;
   TF_DeleteBuffer(buf);
diff --git a/tensorflow/java/src/main/native/utils_jni.cc b/tensorflow/java/src/main/native/utils_jni.cc
new file mode 100644
index 0000000000..069ac05a1c
--- /dev/null
+++ b/tensorflow/java/src/main/native/utils_jni.cc
@@ -0,0 +1,53 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/java/src/main/native/utils_jni.h"
+
+#include "tensorflow/java/src/main/native/exception_jni.h"
+
+void resolveOutputs(JNIEnv* env, const char* type, jlongArray src_op,
+                    jintArray src_index, TF_Output* dst, jint n) {
+  if (env->ExceptionCheck()) return;
+  jint len = env->GetArrayLength(src_op);
+  if (len != n) {
+    throwException(env, kIllegalArgumentException,
+                   "expected %d, got %d %s Operations", n, len, type);
+    return;
+  }
+  len = env->GetArrayLength(src_index);
+  if (len != n) {
+    throwException(env, kIllegalArgumentException,
+                   "expected %d, got %d %s Operation output indices", n, len,
+                   type);
+    return;
+  }
+  jlong* op_handles = env->GetLongArrayElements(src_op, nullptr);
+  jint* indices = env->GetIntArrayElements(src_index, nullptr);
+  for (int i = 0; i < n; ++i) {
+    if (op_handles[i] == 0) {
+      throwException(env, kNullPointerException, "invalid %s (#%d of %d)", type,
+                     i, n);
+      break;
+    }
+    dst[i] = TF_Output{reinterpret_cast<TF_Operation*>(op_handles[i]),
+                       static_cast<int>(indices[i])};
+  }
+  env->ReleaseIntArrayElements(src_index, indices, JNI_ABORT);
+  env->ReleaseLongArrayElements(src_op, op_handles, JNI_ABORT);
+}
+
+
+
+
diff --git a/tensorflow/java/src/main/native/utils_jni.h b/tensorflow/java/src/main/native/utils_jni.h
new file mode 100644
index 0000000000..352298e7de
--- /dev/null
+++ b/tensorflow/java/src/main/native/utils_jni.h
@@ -0,0 +1,33 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_JAVA_UTILS_JNI_H_
+#define TENSORFLOW_JAVA_UTILS_JNI_H_
+
+#include <jni.h>
+
+#include "tensorflow/c/c_api.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif  // __cplusplus
+
+void resolveOutputs(JNIEnv* env, const char* type, jlongArray src_op,
+                    jintArray src_index, TF_Output* dst, jint n);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif  // __cplusplus
+#endif /* TENSORFLOW_JAVA_UTILS_JNI_H_ */
diff --git a/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java b/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java
index c540299bdc..aa6e5f0235 100644
--- a/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java
+++ b/tensorflow/java/src/test/java/org/tensorflow/GraphTest.java
@@ -22,6 +22,7 @@ import static org.junit.Assert.assertTrue;
 
 import java.util.HashSet;
 import java.util.Iterator;
+
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -129,4 +130,24 @@ public class GraphTest {
       // expected exception.
     }
   }
+  
+  @Test
+  public void addGradientsComputationOpsToGraph() {
+    try (Graph g = new Graph()) {
+      Output<Integer> a = TestUtil.constant(g, "A", new int[][] {{1},{2}});
+      Output<Integer> b = TestUtil.placeholder(g, "B", Integer.class);
+      Output<Integer> c = TestUtil.placeholder(g, "C", Integer.class);
+      Output<Integer> ab = TestUtil.matmul(g, "AxB", a, b, false, false);
+      Output<Integer> abc = TestUtil.matmul(g, "AxBxC", ab, c, false, false);
+      
+      Output<?>[] grad = g.addGradients(new Output<?>[] {abc}, new Output<?>[] {b, c}, null);
+      
+      assertNotNull(grad);
+      assertEquals(2, grad.length);
+      assertNotNull(grad[0]);
+      assertEquals(DataType.INT32, grad[0].dataType());
+      assertNotNull(grad[1]);
+      assertEquals(DataType.INT32, grad[1].dataType());
+    }
+  }
 }