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FDNet: Focal Decomposed Network for Efficient, Robust and Practical Time Series Forecasting

Python 3.8 PyTorch 1.11.0 cuDNN 8.2.0 License CC BY-NC-SA

This is the origin Pytorch implementation of FDNet in the following paper: FDNet: Focal Decomposed Network for Efficient, Robust and Practical Time Series Forecasting which has been accepted to Knowledge-Based Systems.

Decomposed Forecasting Formula

It is different from existing rolling and direct forecasting formulas are illustrated in Figure 1. Built upon direct forecasting formula where forecasting processes of prediction elements are decomposed, decomposed forecasting formula further decomposes feature extraction processes of input elements. Hence, FDNet is composed of basic linear projection layers to extract local fine-grained feature maps of input sequence to get rid of conventional ICOMs and canonical convolutions to stabilize feature extraction processes when handling outliers of input sequences.



Figure 1. Connections and differences among three forecasting formulas. Correlations of prediction elements are neglected by direct forecasting formula while universal correlations of input elements are further neglected by our proposed decomposed forecasting formula.

Focal Input Sequence Decomposition

How focal input sequence decomposition works with forecasting networks is depicted in Figure 2. The latest sub-sequence of input sequence has the shortest length but has the most feature extraction layers. When it goes to farther regions, decomposed sub-sequence gets longer and feature map extracted from it gets shallower. Proportions of input sequence comprised by different sub-sequences approximately form a geometric series with common ratio of $\alpha$. We set $\alpha$ to 0.5 throughout following sections and experiments. In fact, $\alpha$ could be set to other positive numbers which are smaller than one, however these make no difference to the essence of focal decomposition. The number of input sub-sequences divided by focal input sequence decomposition method is a hyper-parameter denoted by f. For instance, if input sequence is consecutively splitted into 4 parts by focal decompostion method like Figure 2, then proportions will be {1/2, 1/4, 1/8, 1/8}. The latest sub-sequence takes the proportion of 1/8 instead of 1/16 in order to make the sum of proportions be 1. Furthermore, feature extractions of different sub-sequences and projections of them to output prediction sequence are all mutually independent. As a result, focal input sequence decomposition method effectively allocates complexity levels to different input sub-sequence independently according to their temporal distances with prediction sequence. Networks with focal input sequence decomposition method is now able to deal with LSTI problem without gaining considerable parameters and suffering performance drop with prolonging the input sequence length. When combining FDNet with focal input sequence decomposition, decomposed feature extraction layers in Figure 3 will take formats in Figure 2.



Figure 2. The architecture of focal input sequence decomposition. Final representations of different sub-sequences are from temporally close to far; short to long; deep to shallow.



Figure 3. An overview of the architecture of FDNet. It decomposes feature extraction processes of different input elements and different variates. Its main components are N decomposed feature extractor layers (blue trapezoid), each containing four 2D convolutional layers. Weight Normalization, Gelu activation and res-connection are combined with each 2D convolutional layer.

Requirements

  • Python 3.8.8
  • matplotlib == 3.3.4
  • numpy == 1.20.1
  • pandas == 1.2.4
  • scikit_learn == 0.24.1
  • scipy == 1.9.0
  • torch == 1.11.0

Dependencies can be installed using the following command:

pip install -r requirements.txt

Data

ETT, ECL, Traffic, Exchange, weather and ILI datasets were acquired at: datasets.

Data Preparation

After you acquire raw data of all datasets, please separately place them in corresponding folders at ./data.

We place ETT in the folder ./ETT-data, ECL in the folder ./electricity, Exchange in the folder ./exchage_rate, ILI in the folder ./illness, Traffic in the folder ./traffic and weather in the folder ./weather of here (the folder tree in the link is shown as below) into folder ./data and rename them from ./ETT-data,./electricity, ./exchange_rate, ./illness, ./traffic and ./weather to ./ETT, ./ECL, ./Exchange, ./ILI, ./Traffic and./weather respectively. We rename the file of ECL/Exchange from electricity.csv/ exchange_rate.csv/ national_illness.csv/ traffic.csv to ECL.csv/ Exchange.csv/ ILI.csv/Traffic.csv and rename the last variable of ECL/Exchange/Traffic from OT to original MT_321/ Singapore/ Sensor_861.

|-Autoformer
| |-ETT-data
| | |-ETTh1.csv
| | |-ETTh2.csv
| | |-ETTm1.csv
| | |-ETTm2.csv
| |
| |-electricity
| | |-electricity.csv
| |
| |-exchange_rate
| | |-exchange_rate.csv
| |
| |-illness
| | |-national_illness.csv
| |
| |-traffic
| | |-traffic.csv
| |
| |-weather
| | |-weather.csv

Then you can get the folder tree shown as below:

|-data
| |-ECL
| | |-ECL.csv
| |
| |-ETT
| | |-ETTh1.csv
| | |-ETTh2.csv
| | |-ETTm1.csv
| | |-ETTm2.csv
| |
| |-Exchange
| | |-Exchange.csv
| |
| |-ILI
| | |-ILI.csv
| |
| |-Traffic
| | |-Traffic.csv
| |
| |-weather
| | |-weather.csv

Usage

Commands for training and testing FDNet of all datasets are in ./scripts/FDNet.sh.

More parameter information please refer to main.py.

We provide a complete command for training and testing FDNet:

python -u main.py --model <model> --data <data> --root_path <root_path> --features <features> --label_len <label_len> --pred_len <pred_len> --pyramid <pyramid> --attn_nums <attn_nums> --d_model <d_model> --kernel <kernel> --criterion <criterion> --learning_rate <learning_rate> --dropout <dropout> --batch_size <batch_size> --train_epochs <train_epochs> --itr <itr>

Here we provide a more detailed and complete command description for training and testing the model:

Parameter name Description of parameter
model The model of experiment. This can be set to FDNet
data The dataset name
root_path The root path of the data file
data_path The data file name
features The forecasting task. This can be set to M,S (M : multivariate forecasting, S : univariate forecasting
target Target feature in S task
checkpoints Location of model checkpoints
label_len Input sequence length
pred_len Prediction sequence length
enc_in Input size
c_out Output size
d_model Dimension of model
dropout Dropout
kernel The kernel size
criterion Standardization
itr Experiments times
train_epochs Train epochs of the second stage
batch_size The batch size of training input data
patience Early stopping patience
learning_rate Optimizer learning rate
pyramid The number of input sub-sequences with different sequence lengths divided by focal input sequence decomposition method
attn_nums The number of decomposed feature extraction layers
ICOM Whether combine forecasting formula with ICOM
loss Loss function

Results

The experiment parameters of each data set are formated in the FDNet.sh files in the directory ./scripts/. You can refer to these parameters for experiments, and you can also adjust the parameters to obtain better mse and mae results or draw better prediction figures.



Figure 4. Multivariate forecasting results



Figure 5. Univariate forecasting results

Contact

If you have any questions, feel free to contact Li Shen through Email ([email protected]) or Github issues. Pull requests are highly welcomed!

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Source code of FDNet: Focal Decomposed Network for Efficient, Robust and Practical Time Series Forecasting

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