tensorflow.js中的自定义激活(Swish)
我正在尝试在tensorflow.js中实现一个自定义激活(Swish)函数。我该怎么做呢？
我没有找到任何自定义激活函数的信息，但添加了一个custom layer。所以我实现了一个自定义的层，我在没有分配任何激活的层之后手动添加。它似乎可以工作，但在代码中(尤其是模型定义)相当繁琐。如何直接扩展激活类以获得可以在任何层定义中调用的激活函数？激活函数是在TF.js代码中的https://github.com/tensorflow/tfjs-layers/blob/master/src/activations.ts中定义的。它应该是这样工作的：const dense_layer = tf.layers.dense({units: 8, activation: my_Swish});
我把我的代码放在一起，在那里我扩展了一个层，使其像一个激活函数。这是类Swish。我还尝试通过Swich2类扩展tf.layers.activations，但调用它会产生错误。
errors.ts:48 Uncaught Error: activation: Improper config format: {"_callHook":null,"_addedWeightNames":[],"_stateful":false,"id":1,"activityRegularizer":null,"inputSpec":null,"supportsMasking":true,"_trainableWeights":[],"_nonTrainableWeights":[],"_losses":[],"_updates":[],"_built":false,"inboundNodes":[],"outboundNodes":[],"name":"activation_Activation1","trainable_":true,"initialWeights":null,"_refCount":null,"fastWeightInitDuringBuild":false,"activation":{}}.
'className' and 'config' must set.
at new e (errors.ts:48)
at Lp (generic_utils.ts:227)
at rm (activations.ts:218)
at im (activations.ts:239)
at new e (core.ts:218)
at Object.dense (exports_layers.ts:524)
at tf.html:77我已经在代码中添加了这两个测试用例。只需取消第64行和第66行的注释，即可查看相应的错误。我的tf_test.html (可以在浏览器本地运行)：
<html>
<head>
<!-- Load TensorFlow.js, Plotly for plots -->
<script src="https://cdn.jsdelivr.net/npm/@tensorflow/tfjs/dist/tf.min.js"> </script>
<script src="https://cdn.plot.ly/plotly-latest.min.js"></script>
<!-- Place your code in the script tag below. You can also use an external .js file -->
</head>
<body>
<div id="myDiv"><!-- Plotly chart will be drawn inside this DIV --></div>
<script>
// Notice there is no 'import' statement. 'tf' is available on the index-page
// because of the script tag above.
// custom layer
// https://github.com/tensorflow/tfjs-examples/blob/master/custom-layer/custom_layer.js
// https://gist.github.com/caisq/33ed021e0c7b9d0e728cb1dce399527d
// https://github.com/tensorflow/tfjs-layers/blob/master/src/activations.ts
class Swish extends tf.layers.Layer {
//static className = 'Swish';
constructor(config) {
super(config);
this.alpha = config.alpha;
}
call(input) {
return tf.tidy(() => {
const x = input[0]; //tf.getExactlyOneTensor(input);
return tf.sigmoid(x.mul(this.alpha)).mul(x);
});
}
computeOutputShape(inputShape){
return inputShape;
}
static get className() {
return 'Swish';
}
getConfig() {
const config = {alpha: this.alpha};
const baseConfig = super.getConfig();
Object.assign(config, baseConfig);
return config;
}
}
tf.serialization.registerClass(Swish);
class Swish2 extends tf.layers.activation {
static get className() {return 'Swish2'};
apply(x, alpha = 1) {
return tf.sigmoid(x.mul(this.alpha)).mul(x);
}
}
tf.serialization.registerClass(Swish2);
const sw = new Swish({alpha: 1});
const sw2 = new Swish2(1);
// create Model
const m_in = tf.input({shape: [1]});
// this doesn't work!!! activations have to be defined manually as layers and then added, see below
//const test = tf.layers.dense({units: 8, activation: sw}).apply(m_in);
// sw2 can't be called this way either, yields 'Improper config format' error
//const test2 = tf.layers.dense({units: 8, activation: sw2}).apply(m_in);
const dense1 = tf.layers.dense({units: 8}).apply(m_in);
const swa = sw.apply(dense1);
const m_out = tf.layers.dense({units: 1}).apply(swa);
const model = tf.model({inputs: m_in, outputs: m_out});
</script>
</body>
</html>回答 1
Stack Overflow用户
发布于 2019-08-12 16:50:58
根据文档，tf.layers.dense的激活属性是一个字符串：'elu'|'hardSigmoid'|'linear'|'relu'|'relu6'| 'selu'|'sigmoid'|'softmax'|'softplus'|'softsign'|'tanh'。通过使用tf.layers.activation.layer的实例，将引发以下错误：
激活:配置格式错误：{"_callHook":null，"_addedWeightNames":[]，"_stateful":false，"id":0，"activityRegularizer":null，"inputSpec":null，"supportsMasking":true，"_trainableWeights":[]，"_nonTrainableWeights":[]，"_losses":[]，"_updates":[]，"_built":false，"inboundNodes":[]，"outboundNodes":[]，"name":"activation_Activation1"，"trainable_":true，"initialWeights":null，"_refCount":null，"fastWeightInitDuringBuild":false，“激活”：{}，"alpha":1}。
该错误指示没有设置className，也没有设置配置，因为激活类的getActivation返回一个空对象。查看代码here，我们可以看到，如果激活不是一个字符串，则返回一个没有类名和配置的空层。
设置自定义激活层的正确方法是将其应用为doc中指定的层。
https://stackoverflow.com/questions/57436740
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