| 1 | /**
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| 2 | * @license
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| 3 | * Copyright 2020 Google Inc. All Rights Reserved.
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| 4 | * Licensed under the Apache License, Version 2.0 (the "License");
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| 5 | * you may not use this file except in compliance with the License.
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| 6 | * You may obtain a copy of the License at
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| 7 | *
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| 8 | * http://www.apache.org/licenses/LICENSE-2.0
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| 9 | *
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| 10 | * Unless required by applicable law or agreed to in writing, software
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| 11 | * distributed under the License is distributed on an "AS IS" BASIS,
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| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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| 13 | * See the License for the specific language governing permissions and
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| 14 | * limitations under the License.
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| 15 | * =============================================================================
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| 16 | */
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| 17 | import { customGrad } from '../gradients';
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| 18 | import { convertToTensor } from '../tensor_util_env';
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| 19 | import { cast } from './cast';
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| 20 | import { exp } from './exp';
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| 21 | import { log } from './log';
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| 22 | import { max } from './max';
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| 23 | import { mul } from './mul';
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| 24 | import { op } from './operation';
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| 25 | import { sub } from './sub';
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| 26 | import { sum } from './sum';
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| 27 | /**
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| 28 | * Computes the log softmax.
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| 29 | *
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| 30 | * ```js
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| 31 | * const a = tf.tensor1d([1, 2, 3]);
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| 32 | *
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| 33 | * a.logSoftmax().print(); // or tf.logSoftmax(a)
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| 34 | * ```
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| 35 | *
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| 36 | * ```js
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| 37 | * const a = tf.tensor2d([2, 4, 6, 1, 2, 3], [2, 3]);
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| 38 | *
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| 39 | * a.logSoftmax().print(); // or tf.logSoftmax(a)
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| 40 | * ```
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| 41 | *
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| 42 | * @param logits The logits array.
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| 43 | * @param axis The dimension softmax would be performed on. Defaults to `-1`
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| 44 | * which indicates the last dimension.
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| 45 | *
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| 46 | * @doc {heading: 'Operations', subheading: 'Normalization'}
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| 47 | */
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| 48 | function logSoftmax_(logits, axis = -1) {
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| 49 | const $logits = convertToTensor(logits, 'logits', 'logSoftmax');
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| 50 | if (axis === -1) {
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| 51 | axis = $logits.rank - 1;
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| 52 | }
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| 53 | if (axis !== $logits.rank - 1) {
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| 54 | throw Error('Log Softmax along a non-last dimension is not yet supported. ' +
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| 55 | `Logits was rank ${$logits.rank} and axis was ${axis}`);
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| 56 | }
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| 57 | // const forward: ForwardFunc<Tensor> = (backend, save) => {
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| 58 | // const keepDims = true;
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| 59 | // const xMax = max(logits, axis, true);
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| 60 | // const shifted = sub(logits, xMax);
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| 61 | // const value =
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| 62 | // sub(cast(shifted, 'float32'), log(sum(exp(shifted), axis,
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| 63 | // keepDims)));
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| 64 | // save([value]);
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| 65 | // return value;
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| 66 | // };
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| 67 | // Use a custom gradient for numerical stability.
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| 68 | const customOp = customGrad((logits, save) => {
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| 69 | const keepDims = true;
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| 70 | const xMax = max(logits, axis, true);
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| 71 | const shifted = sub(logits, xMax);
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| 72 | const value = sub(cast(shifted, 'float32'), log(sum(exp(shifted), axis, keepDims)));
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| 73 | save([value]);
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| 74 | const gradFunc = (dy, saved) => {
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| 75 | const [value] = saved;
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| 76 | const keepDims = true;
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| 77 | const softmax = exp(value);
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| 78 | return sub(dy, mul(sum(dy, axis, keepDims), softmax));
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| 79 | };
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| 80 | return { value, gradFunc };
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| 81 | });
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| 82 | return customOp($logits);
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| 83 | // TODO Use Engine.runKernel when CPU/WebGL/WASM backends implement this.
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| 84 | // const inputs: LogSoftmaxInputs = {logits: $logits};
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| 85 | // const attrs: LogSoftmaxAttrs = {axis};
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| 86 | // return ENGINE.runKernel(
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| 87 | // LogSoftmax, inputs as {} as NamedTensorMap,
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| 88 | // attrs as {} as NamedAttrMap);
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| 89 | }
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| 90 | export const logSoftmax = op({ logSoftmax_ });
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| 91 | //# 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