import torch
import torch.nn as nn
import torch.nn.functional as F
from torchvision import datasets, transforms
from nni.compression.torch import FPGMPruner

class Mnist(torch.nn.Module):
    def __init__(self):
        super().__init__()
        self.conv1 = nn.Conv2d(1, 20, 5, 1)
        self.conv2 = nn.Conv2d(20, 50, 5, 1)
        self.fc1 = nn.Linear(4 * 4 * 50, 500)
        self.fc2 = nn.Linear(500, 10)

    def forward(self, x):
        x = F.relu(self.conv1(x))
        x = F.max_pool2d(x, 2, 2)
        x = F.relu(self.conv2(x))
        x = F.max_pool2d(x, 2, 2)
        x = x.view(x.size(0), -1)
        x = F.relu(self.fc1(x))
        x = self.fc2(x)
        return F.log_softmax(x, dim=1)

    def _get_conv_weight_sparsity(self, conv_layer):
        num_zero_filters = (conv_layer.weight.data.sum((1, 2, 3)) == 0).sum()
        num_filters = conv_layer.weight.data.size(0)
        return num_zero_filters, num_filters, float(num_zero_filters)/num_filters

    def print_conv_filter_sparsity(self):
        if isinstance(self.conv1, nn.Conv2d):
            conv1_data = self._get_conv_weight_sparsity(self.conv1)
            conv2_data = self._get_conv_weight_sparsity(self.conv2)
        else:
            # self.conv1 is wrapped as PrunerModuleWrapper
            conv1_data = self._get_conv_weight_sparsity(self.conv1.module)
            conv2_data = self._get_conv_weight_sparsity(self.conv2.module)

        print('conv1: num zero filters: {}, num filters: {}, sparsity: {:.4f}'.format(conv1_data[0], conv1_data[1], conv1_data[2]))
        print('conv2: num zero filters: {}, num filters: {}, sparsity: {:.4f}'.format(conv2_data[0], conv2_data[1], conv2_data[2]))

def train(model, device, train_loader, optimizer):
    model.train()
    for batch_idx, (data, target) in enumerate(train_loader):
        data, target = data.to(device), target.to(device)
        optimizer.zero_grad()
        output = model(data)
        loss = F.nll_loss(output, target)
        if batch_idx % 100 == 0:
            print('{:.2f}%  Loss {:.4f}'.format(100 * batch_idx / len(train_loader), loss.item()))
        if batch_idx == 0:
            model.print_conv_filter_sparsity()
        loss.backward()
        optimizer.step()

def test(model, device, test_loader):
    model.eval()
    test_loss = 0
    correct = 0
    with torch.no_grad():
        for data, target in test_loader:
            data, target = data.to(device), target.to(device)
            output = model(data)
            test_loss += F.nll_loss(output, target, reduction='sum').item()
            pred = output.argmax(dim=1, keepdim=True)
            correct += pred.eq(target.view_as(pred)).sum().item()
    test_loss /= len(test_loader.dataset)

    print('Loss: {:.4f}  Accuracy: {}%)\n'.format(
        test_loss, 100 * correct / len(test_loader.dataset)))


def main():
    torch.manual_seed(0)
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

    trans = transforms.Compose([transforms.ToTensor(), transforms.Normalize((0.1307,), (0.3081,))])
    train_loader = torch.utils.data.DataLoader(
        datasets.MNIST('data', train=True, download=True, transform=trans),
        batch_size=64, shuffle=True)
    test_loader = torch.utils.data.DataLoader(
        datasets.MNIST('data', train=False, transform=trans),
        batch_size=1000, shuffle=True)

    model = Mnist()
    model.to(device)
    model.print_conv_filter_sparsity()

    configure_list = [{
        'sparsity': 0.5,
        'op_types': ['Conv2d']
    }]

    pruner = FPGMPruner(model, configure_list)
    pruner.compress()
    model.to(device)
    optimizer = torch.optim.SGD(model.parameters(), lr=0.01, momentum=0.5)
    for epoch in range(10):
        pruner.update_epoch(epoch)
        print('# Epoch {} #'.format(epoch))
        train(model, device, train_loader, optimizer)
        test(model, device, test_loader)

    pruner.export_model('model.pth', 'mask.pth')

if __name__ == '__main__':
    main()