我对PyTorch dataloader里的shuffle=True的理解_Python

对shuffle=true的理解：

之前不了解shuffle的实际效果，假设有数据a,b,c,d，不知道batch_size=2后打乱，具体是如下哪一种情况：

1.先按顺序取batch，对batch内打乱，即先取a,b，a,b进行打乱；

2.先打乱，再取batch。

证明是第二种

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									shuffle (bool, optional): set to ``true`` to have the data reshuffled 

									at every epoch (default: ``false``).

									if shuffle:

									    sampler = randomsampler(dataset) #此时得到的是索引

补充：简单测试一下pytorch dataloader里的shuffle=true是如何工作的

看代码吧~

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									import sys

									import torch

									import random

									import argparse

									import numpy as np

									import pandas as pd

									import torch.nn as nn

									from torch.nn import functional as f

									from torch.optim import lr_scheduler

									from torchvision import datasets, transforms

									from torch.utils.data import tensordataset, dataloader, dataset

									class dealdataset(dataset):

									    def __init__(self):

									        xy = np.loadtxt(open('./iris.csv','rb'), delimiter=',', dtype=np.float32)

									        #data = pd.read_csv("iris.csv",header=none)

									        #xy = data.values

									        self.x_data = torch.from_numpy(xy[:, 0:-1])

									        self.y_data = torch.from_numpy(xy[:, [-1]])

									        self.len = xy.shape[0]

									    def __getitem__(self, index):

									        return self.x_data[index], self.y_data[index]

									    def __len__(self):

									        return self.len

									dealdataset = dealdataset() 

									train_loader2 = dataloader(dataset=dealdataset,

									                          batch_size=2,

									                          shuffle=true)

									#print(dealdataset.x_data)

									for i, data in enumerate(train_loader2):

									    inputs, labels = data

									    #inputs, labels = variable(inputs), variable(labels)

									    print(inputs)

									    #print("epoch：", epoch, "的第" , i, "个inputs", inputs.data.size(), "labels", labels.data.size())