from __future__ import print_function
from __future__ import division
import torch
import torch.nn as nn
import torch.optim as optim
import numpy as np
import torchvision 
from torchvision import datasets,models,transforms
import matplotlib.pyplot as plt
import time
import os
import copy
print("Pytorch version:",torch.__version__)
print("torchvision version:",torchvision.__version__)

#%%輸入
data_dir="D:\Python\Pytorch\data\hymenoptera_data"
# 從[resnet,alexnet,vgg,squeezenet,desenet,inception]
model_name='squeezenet'
# 數(shù)據(jù)集中類別數(shù)量
num_classes=2
# 訓(xùn)練的批量大小
batch_size=8
# 訓(xùn)練epoch數(shù)
num_epochs=15
# 用于特征提取的標(biāo)志。為FALSE，微調(diào)整個(gè)模型，為TRUE只更新圖層參數(shù)
feature_extract=True

#%%模型訓(xùn)練和驗(yàn)證
device=torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
def train_model(model,dataloaders,criterion,optimizer,num_epochs=25,is_inception=False):
    since=time.time()
    val_acc_history=[]
    best_model_wts=copy.deepcopy(model.state_dict())
    best_acc=0.0
    for epoch in range(num_epochs):
        print('Epoch{}/{}'.format(epoch, num_epochs-1))
        print('-'*10)
        # 每個(gè)epoch都有一個(gè)訓(xùn)練和驗(yàn)證階段
        for phase in['train','val']:
            if phase=='train':
                model.train()
            else:
                model.eval()
                
            running_loss=0.0
            running_corrects=0
            # 迭代數(shù)據(jù)
            for inputs,labels in dataloaders[phase]:
                inputs=inputs.to(device)
                labels=labels.to(device)
                # 梯度置零
                optimizer.zero_grad()
                # 向前傳播
                with torch.set_grad_enabled(phase=='train'):
                    # 獲取模型輸出并計(jì)算損失，開始的特殊情況在訓(xùn)練中他有一個(gè)輔助輸出
                    # 在訓(xùn)練模式下，通過將最終輸出和輔助輸出相加來計(jì)算損耗，在測試中值考慮最終輸出
                    if is_inception and phase=='train':
                        outputs,aux_outputs=model(inputs)
                        loss1=criterion(outputs,labels)
                        loss2=criterion(aux_outputs,labels)
                        loss=loss1+0.4*loss2
                    else:
                        outputs=model(inputs)
                        loss=criterion(outputs,labels)
                        
                    _,preds=torch.max(outputs,1)
                    
                    if phase=='train':
                        loss.backward()
                        optimizer.step()
                        
                # 添加
                running_loss+=loss.item()*inputs.size(0)
                running_corrects+=torch.sum(preds==labels.data)
                
            epoch_loss=running_loss/len(dataloaders[phase].dataset)
            epoch_acc=running_corrects.double()/len(dataloaders[phase].dataset)
            
            print('{}loss : {:.4f} acc:{:.4f}'.format(phase, epoch_loss,epoch_acc))
            
            if phase=='train' and epoch_acc>best_acc:
                best_acc=epoch_acc
                best_model_wts=copy.deepcopy(model.state_dict())
            if phase=='val':
                val_acc_history.append(epoch_acc)
            
        print()

    time_elapsed=time.time()-since
    print('training complete in {:.0f}s'.format(time_elapsed//60, time_elapsed%60))
    print('best val acc:{:.4f}'.format(best_acc))
    
    model.load_state_dict(best_model_wts)
    return model,val_acc_history

#%%設(shè)置模型參數(shù)的.require——grad屬性
def set_parameter_requires_grad(model,feature_extracting):
    if feature_extracting:
        for param in model.parameters():
            param.require_grad=False