Understanding GRU Networks In 2021

Ajay Ohri


Let us understand gru networks. Have you ever given a thought as to how Google’s voice search and Apple’s Siri works? The answer is a recurrent neural network (RNN). They are complex algorithm which works on the same principle as neurons in the human brain. RNN is the initial algorithm that memorizes its input because of an internal memory, which makes it absolutely suitable for machine learning problems that involve chronological data.

Even though RNN are very robust, they go through the trouble of short-term memory. For a lengthy data series, RNN comes across trouble in carrying data from previous steps to later ones. So, if a text paragraph is processed to complete predictions, there are chances that RNN can leave significant information from the start.

While backpropagation RNN undergoes the fading gradient problems where gradients are values are made used to update the weights of neural systems.

Briefly, the fading gradient problems are when the gradient reduces as it gets backpropagated over time, and when it remains too petite, it won’t add value to the learning process as such. 

Hence, in RNN, if few previous levels obtain the slightest gradient, then they discontinue learning. Since these layers don’t learn, RNN can fail to remember what is experienced in a lengthy data series and hence face the short-term memory.

To deal with this short-term memory, GRU and LSTM have come out as solutions.

  1. How does GRUs work?
  2. Difference between LSTM and GRU

1) How does GRUs work?

Before understanding how GRU works, we have to understand what GRU is? 

A Gated Recurrent Unit is a variant of the RNN design and employs a gated process to control and manage the flow of information between cells in the neural networks. Introduced in 2014 by Cho, et al., GRU facilitates capturing dependencies from huge sequential data without excluding information from the prior portion of the series of data. This is performed by its gated units that solve exploding/vanishing gradient problems of traditional RNN’s. Such gates control the information that needs to be discarded or maintained on each step.

GRU also utilizes gates like LSTM, but only two, the gates in GRU are update gates and reset gates; the main components of the GRU model are:- 

  • Update gate

The update gate aids the model to decide how much of the earlier information (from previous time steps) requires flowing along to the future. This is truly strong because the model can choose to copy all the details from the past and eradicate the threat of the fading gradient problem.

  • Reset gate

A reset gate decides how much of the past information to disregard. The reset gate is roughly similar to the Forget gate of LSTM, as it classifies the unrelated data and tells the model to forget this data and move forward without it.

  • Current memory content                                                 

Let’s take an example of a movie:

“Taare Zameen par’ has an important message on the natural approach towards educational success and failure that will click with many kids and parents. It tells you that each child has their talent, and not everyone needs to score 90% in academics. Parents should understand the hidden talent of the child and try to be compassionate. The film pulls off high on many areas and is definitely a must-watch.

The last line illustrates the conclusion or result of the review, so our neural network will study with the help of the reset gate to disregard all other information written above, current memory content uses a reset gate for carrying out like sentiment analysis. Let’s see its equation:-

cmt = tanh (wxt  rt x yht-1)

  • Final Memory at Current time state

Suppose while performing sentiment analysis of a movie review, we found the finest information at the very initial line itself and all other information is of no use, then our model should be capable of sorting the sentiment out from the first line and ignore other text.

It takes the current state input, which requires the Update gate. Hence the Update gate is a necessary precondition for this concluding stage.

2) Difference between LSTM and GRU

LSTM – Long short-term memory is an artificial RNN architecture applied in the area of deep learning. LSTM networks are well-matched to processing, classifying, and making forecasts based on time string data since there can be gaps of the unidentified periods between vital events in a time string.

In 2014 to solve the diminishing gradient problem faced by standard recurrent neural networks (RNN). GRU shares many properties of LSTM. Both algorithms use a gating method to manage the memorization process. Interestingly, GRU is less complex than LSTM and is significantly faster to compute.

The main difference between GRU and LSTM is that LSTM has three gates that are input, output, forget, while GRU has two gates that are reset and update while. GRU is less intricate than LSTM because it has fewer gates.


GRU is better than LSTM as it is easy to modify and doesn’t need memory units. Therefore, faster to train than LSTM and give as per performance. If the data series is small, then GRU is chosen; otherwise, LSTM for the larger data series. GRU reveals the entire memory and veiled layers, but LSTM doesn’t. LSTM and GRU are required in complex problem domains like machine translation, speech recognition, Speech Synthesis, Sentiment Analysis, Stock Price Prediction, and Machine Comprehension, and more.

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