@tensorflow/tfjs-core
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Hardware-accelerated JavaScript library for machine intelligence
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JavaScript
/**
* @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 { customGrad } from '../gradients';
import { convertToTensor } from '../tensor_util_env';
import { mul } from './mul';
import { neg } from './neg';
import { op } from './operation';
import { sigmoid } from './sigmoid';
import { softplus } from './softplus';
/**
* Computes log sigmoid of the input `tf.Tensor` element-wise:
* `logSigmoid(x)`. For numerical stability, we use `-tf.softplus(-x)`.
*
* ```js
* const x = tf.tensor1d([0, 1, -1, .7]);
*
* x.logSigmoid().print(); // or tf.logSigmoid(x)
* ```
* @param x The input tensor.
*
* @doc {heading: 'Operations', subheading: 'Basic math'}
*/
function logSigmoid_(x) {
const $x = convertToTensor(x, 'x', 'logSigmoid');
// Use a custom gradient to maintain previous implementation.
// There is no LogSigmoid kernel in TF so we can't use engine.runKernel
// directly
const customOp = customGrad((x) => {
// TODO(yassogba) we can remove the chained softplus call here only
// after backends have modualrized softplus at which point we can call
// engine runKernel(..., Sotfplus, ...) directly.
const value = neg(softplus(neg(x)));
const gradFunc = (dy) => {
const derX = mul(dy, sigmoid(neg(x)));
return derX;
};
return { value, gradFunc };
});
return customOp($x);
}
export const logSigmoid = op({ logSigmoid_ });
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