Add string dtype to Tensor (#1408)

Add `string` dtype to `Tensor`.

This opens the door for adding Python's [`string_ops`](https://www.tensorflow.org/api_docs/python/tf/strings) to TensorFlow.js, which are used for text-based models, and for adding pre-processing layers that operate on strings.

Details:
- dtype was not added as a generic to the Tensor class in order to keep compiler errors simple and code backwards compatible.
- dataSync() can be optionally typed to cast its result. E.g. `t.dataSync<'string'>()` returns `string[]` while `t.dataSync()` returns `TypedArray` for backwards compatibility.
- `layers` and `converter` pass with this build. `node` has 30ish failed tests since `string` is an unknown dtype.
- Only `clone`, `reshape` and `cast` work with strings at this point to keep this PR small. Other ops will get the functionality in a follow-up PR.
- Added unit tests to assert that numeric ops throw on string tensors.
- Backends now should support dtype `string` in their `register/write/read` methods.
- Added a vscode config to do debugging directly from vscode

FEATURE

.vscode/launch.json

@@ -0,0 +1,19 @@
+{
+  // Use IntelliSense to learn about possible attributes.
+  // Hover to view descriptions of existing attributes.
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "type": "chrome",
+      "request": "attach",
+      "name": "Attach Karma Chrome",
+      "address": "localhost",
+      "port": 9333,
+      "pathMapping": {
+        "/": "${workspaceRoot}",
+        "/base/": "${workspaceRoot}/"
+      }
+    }
+  ]
+}

karma.conf.js

@@ -89,7 +89,9 @@ module.exports = function(config) {
       chrome_with_swift_shader: {
         base: 'Chrome',
         flags: ['--blacklist-accelerated-compositing', '--blacklist-webgl']
-      }
+      },
+      chrome_debugging:
+          {base: 'Chrome', flags: ['--remote-debugging-port=9333']}
     },
     client: {jasmine: {random: false}, args: args}
   });

src/buffer_test.ts

@@ -0,0 +1,73 @@
+/**
+ * @license
+ * Copyright 2018 Google LLC. 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.
+ * =============================================================================
+ */
+
+import * as tf from './index';
+import {describeWithFlags} from './jasmine_util';
+import {ALL_ENVS, expectArraysClose, expectArraysEqual} from './test_util';
+
+describeWithFlags('tf.buffer', ALL_ENVS, () => {
+  it('float32', () => {
+    const buff = tf.buffer([1, 2, 3], 'float32');
+    buff.set(1.3, 0, 0, 0);
+    buff.set(2.9, 0, 1, 0);
+    expect(buff.get(0, 0, 0)).toBeCloseTo(1.3);
+    expect(buff.get(0, 0, 1)).toBeCloseTo(0);
+    expect(buff.get(0, 0, 2)).toBeCloseTo(0);
+    expect(buff.get(0, 1, 0)).toBeCloseTo(2.9);
+    expect(buff.get(0, 1, 1)).toBeCloseTo(0);
+    expect(buff.get(0, 1, 2)).toBeCloseTo(0);
+    expectArraysClose(buff.toTensor(), [1.3, 0, 0, 2.9, 0, 0]);
+    expectArraysClose(buff.values, new Float32Array([1.3, 0, 0, 2.9, 0, 0]));
+  });
+
+  it('int32', () => {
+    const buff = tf.buffer([2, 3], 'int32');
+    buff.set(1.3, 0, 0);
+    buff.set(2.1, 1, 1);
+    expect(buff.get(0, 0)).toEqual(1);
+    expect(buff.get(0, 1)).toEqual(0);
+    expect(buff.get(0, 2)).toEqual(0);
+    expect(buff.get(1, 0)).toEqual(0);
+    expect(buff.get(1, 1)).toEqual(2);
+    expect(buff.get(1, 2)).toEqual(0);
+    expectArraysClose(buff.toTensor(), [1, 0, 0, 0, 2, 0]);
+    expectArraysClose(buff.values, new Int32Array([1, 0, 0, 0, 2, 0]));
+  });
+
+  it('bool', () => {
+    const buff = tf.buffer([4], 'bool');
+    buff.set(true, 1);
+    buff.set(true, 2);
+    expect(buff.get(0)).toBeFalsy();
+    expect(buff.get(1)).toBeTruthy();
+    expect(buff.get(2)).toBeTruthy();
+    expect(buff.get(3)).toBeFalsy();
+    expectArraysClose(buff.toTensor(), [0, 1, 1, 0]);
+    expectArraysClose(buff.values, new Uint8Array([0, 1, 1, 0]));
+  });
+
+  it('string', () => {
+    const buff = tf.buffer([2, 2], 'string');
+    buff.set('first', 0, 0);
+    buff.set('third', 1, 0);
+    expect(buff.get(0, 0)).toEqual('first');
+    expect(buff.get(0, 1)).toBeFalsy();
+    expect(buff.get(1, 0)).toEqual('third');
+    expect(buff.get(1, 1)).toBeFalsy();
+    expectArraysEqual(buff.toTensor(), ['first', null, 'third', null]);
+  });
+});

src/engine.ts

@@ -21,9 +21,9 @@ import {backpropagateGradients, getFilteredNodesXToY, NamedGradientMap, TapeNode
 import {DataId, Tensor, Tensor3D, Variable} from './tensor';
 import {NamedTensorMap, NamedVariableMap, TensorContainer} from './tensor_types';
 import {getTensorsInContainer, isTensorInList} from './tensor_util';
-import {DataType, TypedArray} from './types';
+import {DataType, DataValues} from './types';
 import * as util from './util';
-import {makeOnesTypedArray, now, sizeFromShape} from './util';
+import {bytesFromStringArray, makeOnesTypedArray, now, sizeFromShape} from './util';
 
 /**
  * A function that computes an output. The save function is for saving tensors
@@ -42,7 +42,7 @@ export type CustomGradientFunc<T extends Tensor> = (...args: Tensor[]) => {
 
 export type MemoryInfo = {
   numTensors: number; numDataBuffers: number; numBytes: number;
-  unreliable?: boolean;
+  unreliable?: boolean; reasons: string[];
 };
 
 type KernelProfile = {
@@ -85,6 +85,7 @@ export class Engine implements TensorManager, DataMover {
   private nextTapeNodeId = 0;
   private numBytes = 0;
   private numTensors = 0;
+  private numStringTensors = 0;
   private numDataBuffers = 0;
 
   private profiling = false;
@@ -102,6 +103,7 @@ export class Engine implements TensorManager, DataMover {
 
   private tensorInfo = new WeakMap<DataId, {
     backend: KernelBackend,
+    bytes: number,
     dtype: DataType,
     shape: number[],
     refCount: number
@@ -250,18 +252,26 @@ export class Engine implements TensorManager, DataMover {
         this.tensorInfo.get(a.dataId).refCount :
         0;
     this.numTensors++;
+    if (a.dtype === 'string') {
+      this.numStringTensors++;
+    }
     if (refCount === 0) {
       this.numDataBuffers++;
 
-      // Don't count bytes for complex numbers as they are counted by their
-      // components.
-      if (a.dtype !== 'complex64') {
-        this.numBytes +=
-            util.sizeFromShape(a.shape) * util.bytesPerElement(a.dtype);
+      // Bytes for complex numbers are counted by their components. Bytes for
+      // string tensors are counted when writing values.
+      let bytes = 0;
+      if (a.dtype !== 'complex64' && a.dtype !== 'string') {
+        bytes = util.sizeFromShape(a.shape) * util.bytesPerElement(a.dtype);
       }
-      this.tensorInfo.set(
-          a.dataId,
-          {backend: this.backend, dtype: a.dtype, shape: a.shape, refCount: 0});
+      this.tensorInfo.set(a.dataId, {
+        backend: this.backend,
+        dtype: a.dtype,
+        shape: a.shape,
+        bytes,
+        refCount: 0
+      });
+      this.numBytes += bytes;
       this.backend.register(a.dataId, a.shape, a.dtype);
     }
     this.tensorInfo.get(a.dataId).refCount++;
@@ -285,17 +295,19 @@ export class Engine implements TensorManager, DataMover {
       this.keepTensors.delete(a.id);
     }
     this.numTensors--;
-    const refCount = this.tensorInfo.get(a.dataId).refCount;
+    if (a.dtype === 'string') {
+      this.numStringTensors--;
+    }
+    const info = this.tensorInfo.get(a.dataId);
+    const refCount = info.refCount;
     if (refCount <= 1) {
-      const info = this.tensorInfo.get(a.dataId);
-      info.backend.disposeData(a.dataId);
-      this.numDataBuffers--;
       // Don't count bytes for complex numbers as they are counted by their
       // components.
       if (a.dtype !== 'complex64') {
-        this.numBytes -=
-            util.sizeFromShape(a.shape) * util.bytesPerElement(a.dtype);
+        this.numBytes -= info.bytes;
       }
+      this.numDataBuffers--;
+      info.backend.disposeData(a.dataId);
       this.tensorInfo.delete(a.dataId);
     } else {
       this.tensorInfo.get(a.dataId).refCount--;
@@ -318,6 +330,15 @@ export class Engine implements TensorManager, DataMover {
     info.numTensors = this.numTensors;
     info.numDataBuffers = this.numDataBuffers;
     info.numBytes = this.numBytes;
+    if (this.numStringTensors > 0) {
+      info.unreliable = true;
+      if (info.reasons == null) {
+        info.reasons = [];
+      }
+      info.reasons.push(
+          'Memory usage by string tensors is approximate ' +
+          '(2 bytes per character)');
+    }
     return info;
   }
 
@@ -457,6 +478,9 @@ export class Engine implements TensorManager, DataMover {
       f: () => T, xs: Tensor[], dy?: T,
       allowNoGradients = false): {value: T, grads: Tensor[]} {
     util.assert(xs.length > 0, 'gradients() received an empty list of xs.');
+    if (dy != null && dy.dtype !== 'float32') {
+      throw new Error(`dy must have 'float32' dtype, but has '${dy.dtype}'`);
+    }
 
     return this.tidy('gradients', () => {
       const y = f();
@@ -537,8 +561,15 @@ export class Engine implements TensorManager, DataMover {
   }
 
   // Forwarding to backend.
-  write(dataId: DataId, values: TypedArray): void {
+  write(dataId: DataId, values: DataValues): void {
     const info = this.tensorInfo.get(dataId);
+    // Bytes for string tensors are counted when writing.
+    if (info.dtype === 'string') {
+      const newBytes = bytesFromStringArray(values as string[]);
+      this.numBytes += newBytes - info.bytes;
+      info.bytes = newBytes;
+    }
+
     if (this.backend !== info.backend) {
       // Delete the tensor from the old backend and move it to the new backend.
       info.backend.disposeData(dataId);
@@ -547,12 +578,12 @@ export class Engine implements TensorManager, DataMover {
     }
     this.backend.write(dataId, values);
   }
-  readSync(dataId: DataId): TypedArray {
+  readSync(dataId: DataId): DataValues {
     // Route the read to the correct backend.
     const info = this.tensorInfo.get(dataId);
     return info.backend.readSync(dataId);
   }
-  read(dataId: DataId): Promise<TypedArray> {
+  read(dataId: DataId): Promise<DataValues> {
     // Route the read to the correct backend.
     const info = this.tensorInfo.get(dataId);
     return info.backend.read(dataId);

src/engine_test.ts

@@ -20,7 +20,7 @@ import {describeWithFlags} from './jasmine_util';
 import {MathBackendCPU} from './kernels/backend_cpu';
 import {MathBackendWebGL} from './kernels/backend_webgl';
 import {Tensor} from './tensor';
-import {ALL_ENVS, expectArraysClose, expectArraysEqual, expectNumbersClose, WEBGL_ENVS} from './test_util';
+import {ALL_ENVS, CPU_ENVS, expectArraysClose, expectArraysEqual, expectNumbersClose, WEBGL_ENVS} from './test_util';
 
 describeWithFlags('fromPixels + regular math op', WEBGL_ENVS, () => {
   it('debug mode does not error when no nans', () => {
@@ -361,6 +361,74 @@ describeWithFlags('memory', ALL_ENVS, () => {
     expect(sum.dtype).toBe('int32');
     expectArraysClose(sum, [1 + 1 + 0 + 1]);
   });
+
+  it('string tensor', () => {
+    const a = tf.tensor([['a', 'bb'], ['c', 'd']]);
+
+    expect(tf.memory().numTensors).toBe(1);
+    expect(tf.memory().numBytes).toBe(10);  // 5 letters, each 2 bytes.
+
+    a.dispose();
+
+    expect(tf.memory().numTensors).toBe(0);
+    expect(tf.memory().numBytes).toBe(0);
+  });
+
+  it('unreliable is true for string tensors', () => {
+    tf.tensor('a');
+    const mem = tf.memory();
+    expect(mem.unreliable).toBe(true);
+    const expectedReason = 'Memory usage by string tensors is approximate ' +
+        '(2 bytes per character)';
+    expect(mem.reasons.indexOf(expectedReason) >= 0).toBe(true);
+  });
+});
+
+describeWithFlags('memory webgl', WEBGL_ENVS, () => {
+  it('unreliable is falsy/not present when all tensors are numeric', () => {
+    tf.tensor(1);
+    const mem = tf.memory();
+    expect(mem.numTensors).toBe(1);
+    expect(mem.numDataBuffers).toBe(1);
+    expect(mem.numBytes).toBe(4);
+    expect(mem.unreliable).toBeFalsy();
+  });
+});
+
+describeWithFlags('memory cpu', CPU_ENVS, () => {
+  it('unreliable is true due to auto gc', () => {
+    tf.tensor(1);
+    const mem = tf.memory();
+    expect(mem.numTensors).toBe(1);
+    expect(mem.numDataBuffers).toBe(1);
+    expect(mem.numBytes).toBe(4);
+    expect(mem.unreliable).toBe(true);
+
+    const expectedReason =
+        'The reported memory is an upper bound. Due to automatic garbage ' +
+        'collection, the true allocated memory may be less.';
+    expect(mem.reasons.indexOf(expectedReason) >= 0).toBe(true);
+  });
+
+  it('unreliable is true due to both auto gc and string tensors', () => {
+    tf.tensor(1);
+    tf.tensor('a');
+
+    const mem = tf.memory();
+    expect(mem.numTensors).toBe(2);
+    expect(mem.numDataBuffers).toBe(2);
+    expect(mem.numBytes).toBe(6);
+    expect(mem.unreliable).toBe(true);
+
+    const expectedReasonGC =
+        'The reported memory is an upper bound. Due to automatic garbage ' +
+        'collection, the true allocated memory may be less.';
+    expect(mem.reasons.indexOf(expectedReasonGC) >= 0).toBe(true);
+    const expectedReasonString =
+        'Memory usage by string tensors is approximate ' +
+        '(2 bytes per character)';
+    expect(mem.reasons.indexOf(expectedReasonString) >= 0).toBe(true);
+  });
 });
 
 describeWithFlags('profile', ALL_ENVS, () => {

src/environment.ts

@@ -101,11 +101,10 @@ export class Environment {
    *   (undisposed) at this time, which is ≤ the number of tensors
    *   (e.g. `a.reshape(newShape)` makes a new Tensor that shares the same
    *   data buffer with `a`).
-   * - `unreliable`: `Optional` `boolean`:
-   *    - On WebGL, not present (always reliable).
-   *    - On CPU, true. Due to automatic garbage collection, these numbers
-   *     represent undisposed tensors, i.e. not wrapped in `tidy()`, or
-   *     lacking a call to `tensor.dispose()`.
+   * - `unreliable`: True if the memory usage is unreliable. See `reasons` when
+   *    `unrealible` is true.
+   * - `reasons`: `string[]`, reasons why the memory is unreliable, present if
+   *    `unreliable` is true.
    */
   /** @doc {heading: 'Performance', subheading: 'Memory'} */
   static memory(): MemoryInfo {

src/index.ts

@@ -48,7 +48,7 @@ export {RMSPropOptimizer} from './optimizers/rmsprop_optimizer';
 export {SGDOptimizer} from './optimizers/sgd_optimizer';
 export {Scalar, Tensor, Tensor1D, Tensor2D, Tensor3D, Tensor4D, TensorBuffer, variable, Variable} from './tensor';
 export {NamedTensorMap} from './tensor_types';
-export {DataType, Rank, ShapeMap} from './types';
+export {DataType, DataTypeMap, DataValues, Rank, ShapeMap} from './types';
 
 export * from './ops/ops';
 export {LSTMCellFunc} from './ops/lstm';

src/jasmine_util.ts

@@ -93,7 +93,7 @@ export interface TestEnv {
 
 export let TEST_ENVS: TestEnv[] = [
   {
-    name: 'test-webgl1',
+    name: 'webgl1',
     factory: () => new MathBackendWebGL(),
     features: {
       'WEBGL_VERSION': 1,
@@ -102,7 +102,7 @@ export let TEST_ENVS: TestEnv[] = [
     }
   },
   {
-    name: 'test-webgl2',
+    name: 'webgl2',
     factory: () => new MathBackendWebGL(),
     features: {
       'WEBGL_VERSION': 2,
@@ -111,7 +111,7 @@ export let TEST_ENVS: TestEnv[] = [
     }
   },
   {
-    name: 'test-cpu',
+    name: 'cpu',
     factory: () => new MathBackendCPU(),
     features: {'HAS_WEBGL': false}
   }