为什么在这个简单的NN示例中，Tensorflow 100x比convnetjs慢?

I've been working with convnetjs for 1 year and now I want to move on to more powerful and fast libraries. I thought Tensorflow would be orders of magnitude faster than a JS library, so I wrote a simple neural network for both libraries and did some tests. It is a 3-5-5-1 neural network, trained on one single example for a certain number of epochs with SGD and RELU layers.I've been working with convnetjs for 1 year and