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+# Numerical Operations
+import csv
+import math
+import os
+
+import numpy as np
+# Reading/Writing Data
+import pandas as pd
+# Pytorch
+import torch
+import torch.nn as nn
+from sklearn.feature_selection import SelectFromModel
+from sklearn.linear_model import RidgeCV
+from torch.utils.data import Dataset, DataLoader, random_split
+# For Progress Bar
+from tqdm import tqdm
+
+
+# For plotting learning curve
+# from torch.utils.tensorboard import SummaryWriter
+
+def same_seed(seed):
+    """Fixes random number generator seeds for reproducibility."""
+    torch.backends.cudnn.deterministic = True
+    torch.backends.cudnn.benchmark = False
+    np.random.seed(seed)
+    torch.manual_seed(seed)
+    if torch.cuda.is_available():
+        torch.cuda.manual_seed_all(seed)
+
+
+def train_valid_split(data_set, valid_ratio, seed):
+    """Split provided training data into training set and validation set"""
+    valid_set_size = int(valid_ratio * len(data_set))
+    train_set_size = len(data_set) - valid_set_size
+    train_set, valid_set = random_split(data_set, [train_set_size, valid_set_size],
+                                        generator=torch.Generator().manual_seed(seed))
+    return np.array(train_set), np.array(valid_set)
+
+
+def predict(test_loader, model, device):
+    model.eval()  # Set your model to evaluation mode.
+    preds = []
+    for x in tqdm(test_loader):
+        x = x.to(device)
+        with torch.no_grad():
+            pred = model(x)
+            preds.append(pred.detach().cpu())
+    preds = torch.cat(preds, dim=0).numpy()
+    return preds
+
+
+class COVID19Dataset(Dataset):
+    """
+    x: Features.
+    y: Targets, if none, do prediction.
+    """
+
+    def __init__(self, x, y=None):
+        if y is None:
+            self.y = y
+        else:
+            self.y = torch.FloatTensor(y)
+        self.x = torch.FloatTensor(x)
+
+    def __getitem__(self, idx):
+        if self.y is None:
+            return self.x[idx]
+        else:
+            return self.x[idx], self.y[idx]
+
+    def __len__(self):
+        return len(self.x)
+
+
+class MyModel(nn.Module):
+    def __init__(self, input_dim):
+        super(MyModel, self).__init__()
+        self.layers = nn.Sequential(
+            nn.Linear(input_dim, 16),
+            nn.ReLU(),
+            nn.Linear(16, 4),
+            nn.ReLU(),
+            nn.Linear(4, 2),
+            nn.ReLU(),
+            nn.Linear(2, 1)
+        )
+
+    def forward(self, x):
+        x = self.layers(x)
+        x = x.squeeze(1)  # (B, 1) -> (B)
+        return x
+
+
+def select_feat(train_data, valid_data, test_data, select_all=True):
+    """Selects useful features to perform regression"""
+    y_train, y_valid = train_data[:, -1], valid_data[:, -1]
+    raw_x_train, raw_x_valid, raw_x_test = train_data[:, :-1], valid_data[:, :-1], test_data
+
+    if select_all:
+        feat_idx = list(range(raw_x_train.shape[1]))
+    else:
+        selection = SelectFromModel(RidgeCV()).fit(raw_x_train, y_train)
+        feat_idx = [i for i, support in enumerate(selection.get_support()) if support]
+        print('selected feature list: ', feat_idx)
+
+    return raw_x_train[:, feat_idx], raw_x_valid[:, feat_idx], raw_x_test[:, feat_idx], y_train, y_valid
+
+
+def trainer(train_loader, valid_loader, model, config, device):
+    criterion = nn.MSELoss(reduction='mean')  # Define your loss function, do not modify this.
+
+    # Define your optimization algorithm.
+    # optimizer = torch.optim.SGD(model.parameters(), lr=1e-5, momentum=0.1)
+    optimizer = torch.optim.Adam(model.parameters(), weight_decay=0.1, lr=1e-3)
+
+    # writer = SummaryWriter()  # Writer of tensoboard.
+
+    if not os.path.isdir('./models'):
+        os.mkdir('./models')  # Create directory of saving models.
+
+    n_epochs, best_loss, step, early_stop_count = config['n_epochs'], math.inf, 0, 0
+
+    for epoch in range(n_epochs):
+        model.train()  # Set your model to train mode.
+        loss_record = []
+
+        # tqdm is a package to visualize your training progress.
+        train_pbar = tqdm(train_loader, position=0, leave=True)
+
+        for x, y in train_pbar:
+            optimizer.zero_grad()  # Set gradient to zero.
+            x, y = x.to(device), y.to(device)  # Move your data to device.
+            pred = model(x)
+            loss = criterion(pred, y)
+            loss.backward()  # Compute gradient(backpropagation).
+            optimizer.step()  # Update parameters.
+            step += 1
+            loss_record.append(loss.detach().item())
+
+            # Display current epoch number and loss on tqdm progress bar.
+            train_pbar.set_description(f'Epoch [{epoch + 1}/{n_epochs}]')
+            train_pbar.set_postfix({'loss': loss.detach().item()})
+
+        mean_train_loss = sum(loss_record) / len(loss_record)
+        # writer.add_scalar('Loss/train', mean_train_loss, step)
+
+        model.eval()  # Set your model to evaluation mode.
+        loss_record = []
+        for x, y in valid_loader:
+            x, y = x.to(device), y.to(device)
+            with torch.no_grad():
+                pred = model(x)
+                loss = criterion(pred, y)
+
+            loss_record.append(loss.item())
+
+        mean_valid_loss = sum(loss_record) / len(loss_record)
+        print(f'Epoch [{epoch + 1}/{n_epochs}]: Train loss: {mean_train_loss:.4f}, Valid loss: {mean_valid_loss:.4f}')
+        # writer.add_scalar('Loss/valid', mean_valid_loss, step)
+
+        if mean_valid_loss < best_loss:
+            best_loss = mean_valid_loss
+            torch.save(model.state_dict(), config['save_path'])  # Save your best model
+            print('Saving model with loss {:.3f}...'.format(best_loss))
+            early_stop_count = 0
+        else:
+            early_stop_count += 1
+
+        if early_stop_count >= config['early_stop']:
+            print('\nModel is not improving, so we halt the training session.')
+            print('Final best loss: ', best_loss)
+            return best_loss
+    print('Final best loss: ', best_loss)
+    return best_loss
+
+
+device = 'cuda' if torch.cuda.is_available() else 'cpu'
+config = {
+    'seed': 12345,  # Your seed number, you can pick your lucky number. :)
+    'select_all': False,  # Whether to use all features.
+    'valid_ratio': 0.2,  # validation_size = train_size * valid_ratio
+    'n_epochs': 10000,  # Number of epochs.
+    'batch_size': 512,
+    'early_stop': 500,  # If model has not improved for this many consecutive epochs, stop training.
+    'save_path': './models/model.ckpt'  # Your model will be saved here.
+}
+
+# Set seed for reproducibility
+same_seed(config['seed'])
+
+# train_data size: 2699 x 118 (id + 37 states + 16 features x 5 days)
+# test_data size: 1078 x 117 (without last day's positive rate)
+train_data, test_data = pd.read_csv('./covid.train.csv').values, pd.read_csv('./covid.test.csv').values
+train_data, valid_data = train_valid_split(train_data, config['valid_ratio'], config['seed'])
+
+# Print out the data size.
+print(f"""train_data size: {train_data.shape} 
+valid_data size: {valid_data.shape} 
+test_data size: {test_data.shape}""")
+
+# Select features
+x_train, x_valid, x_test, y_train, y_valid = select_feat(train_data, valid_data, test_data, config['select_all'])
+
+# Print out the number of features.
+print(f'number of features: {x_train.shape[1]}')
+
+train_dataset, valid_dataset, test_dataset = COVID19Dataset(x_train, y_train), \
+                                             COVID19Dataset(x_valid, y_valid), \
+                                             COVID19Dataset(x_test)
+
+# Pytorch data loader loads pytorch dataset into batches.
+train_loader = DataLoader(train_dataset, batch_size=config['batch_size'], shuffle=True, pin_memory=True)
+valid_loader = DataLoader(valid_dataset, batch_size=config['batch_size'], shuffle=True, pin_memory=True)
+test_loader = DataLoader(test_dataset, batch_size=config['batch_size'], shuffle=False, pin_memory=True)
+
+if __name__ == '__main__':
+    """
+    Final result: 
+    Score: 0.92776
+    Public score: 0.87331
+    """
+    model = MyModel(input_dim=x_train.shape[1]).to(device)  # put your model and data on the same computation device.
+    trainer(train_loader, valid_loader, model, config, device)
+
+    # best_final_loss = math.inf
+    best_seed = config['seed']
+    # for i in range(1000):
+    #     config['seed'] = i
+    #     model = MyModel(input_dim=x_train.shape[1]).to(device)
+    #     best_loss = trainer(train_loader, valid_loader, model, config, device)
+    #     if best_loss < best_final_loss:
+    #         best_seed = i
+
+    config['seed'] = best_seed
+    model = MyModel(input_dim=x_train.shape[1]).to(device)
+    trainer(train_loader, valid_loader, model, config, device)
+
+
+    def save_pred(preds, file):
+        """ Save predictions to specified file """
+        with open(file, 'w') as fp:
+            writer = csv.writer(fp)
+            writer.writerow(['id', 'tested_positive'])
+            for i, p in enumerate(preds):
+                writer.writerow([i, p])
+
+
+    print(config)
+    model = MyModel(input_dim=x_train.shape[1]).to(device)
+    model.load_state_dict(torch.load(config['save_path']))
+    preds = predict(test_loader, model, device)
+    save_pred(preds, 'pred.csv')