torch.arange(1,10) #产生 1~9 组成的一维张量，第一个值缺省就从0开始

torch.transpose(x, 0, 1) #这就是把x矩阵的0维和1维度交换，即转置

torch.transpose(x, 1, 0) #这个和上面的是一样

torch.transpose(x, -2, -1) #这个将最后一个维度和倒数第二个维度交换，比如有一个张量为[3x4x5]，那么执行转换以后变为[3x5x4]

t = torch.full([3,1,4,1,5], 5)
t.squeeze(1) #shape:[3,4,1,5], 同 torch.squeeze(t,1)

normal(mean, std, *, generator=None, out=None)

torch.normal(mean=0.,std=1.,size=(2,2))  #我们从一个标准正态分布N～(0,1)，提取一个2x2的矩阵

* k #取的元素个数
* dim #选取的维度
* largest #从大到小取元素
* sorted #返回的结果按照顺序返回
* 返回值第一个为结果，第二个为结果的下标

	m = torch.randn([2,5,3]) #shape: [2,5,3]
	m.sum(0) #shape: [5,3]
	m.sum(0, keepdim = Ture) #shape: [1,5,3]
	m.sum(1) #shape: [2,3]
	m.sum(1, keepdim = Ture) #shape: [2,1,3]

	#---cat---
	#torch.cat(tensors, dim=d, *, out=None)
	#tensors 可以是多个张量
	#除了要进行cat的维度外，其余维度要和待拼接的tensor保持一致
	input = torch.ones(1,2,5)
	input2 = torch.ones(2,2,5)
	output = torch.cat([input2, input,input],0)
	print(output.shape) #shape [4,2,5]

	#---stack---
	#torch.stack(tensors, dim=d, *, out=None)
	#沿新维度连接一系列张量，所有张量都需要具有相同的大小
	input = torch.ones(1,2,5)
	output = torch.stack([input, input,input],0) #在原来的0维前添加
	print(output.shape) #shape: 3,1,2,5
	output = torch.stack([input, input,input],2) #在原来的2维前添加
	print(output.shape) #shape: 1,2,3,5

	for name,param in rbf.named_parameters():
		if param.requires_grad:
			print("learned:",name)

#Dataset是一个数据处理类。当我们继承了一个 Dataset类之后，我们需要重写 len 方法，getitem 方法

#接收一个索引，返回一个样本，和数组很像
#支持迭代，支持下标索引

from torch.utils.data import Dataset, DataLoader
class MyDataset(Dataset):
    def __init__(self):
        self.x = torch.linspace(1,10,10)
        self.len = len(self.x)

    #获取数据
    def __getitem__(self, index):
        return self.x[index] 

    def __len__(self):
        return self.len

#DataLoader
torch.utils.data.DataLoader(
	dataset,  #需要提取数据的数据集，Dataset对象
	batch_size=1,  #每一次装载样本的个数
	shuffle=None,  #进行新一轮epoch时是否要重新洗牌，Boolean型
	sampler=None,
	batch_sampler=None,
	num_workers=0, 	#是否多进程读取机制
	collate_fn=None,
	pin_memory=False,
	drop_last=False, #当样本数不能被batchsize整除时， 是否舍弃最后一批数据
	timeout=0,
	worker_init_fn=None,
	multiprocessing_context=None,
	generator=None,
	*,
	prefetch_factor=2,
	persistent_workers=False,
	pin_memory_device='') 

class MyDataset(Dataset):
    def __init__(self):
        self.x = torch.linspace(11,20,10)
        self.y = torch.linspace(1,10,10)
        self.len = len(self.x)

    #获取数据
    def __getitem__(self, index):
        return self.x[index], self.y[index]

    def __len__(self):
        return self.len

mydataset = MyDataset()

mytrainload = DataLoader(dataset=mydataset,
		batch_size = 5,     #mydataset长度为：10/5
		shuffle=False)

#遍历数据集
for step,(batch_x, batch_y) in enumerate(mytrainload):
	print('step:', step,'| batch x: ', batch_x.numpy(), '| batch y: ', batch_y.numpy())
#输出数据
#step: 0 | batch x: [11. 12. 13. 14. 15.] | batch y: [1. 2. 3. 4. 5.]
#step: 1 | batch x: [16. 17. 18. 19. 20.] | batch y: [6. 7. 8. 9. 10.]	

input = torch.randn(5, 12) #相当于5个样本，每个样本12个特征
fc = nn.Linear(12, 15) #每个向量由12个特征, 输出15个特征
output = fc(input) #输出维度[5*15]

import pandas as pd
import numpy as np
import torch
from torch import nn 
from torch.nn import functional as F
import matplotlib.pyplot as plt
import torch.utils.data as Data
import torch.optim as optim
from torch.nn import init

#二元数据
def prepare_data_2d():
	num_inputs = 2
	num_examples = 1000
	true_w = [2, -3.4]
	true_b = 4.2
	features=torch.tensor(np.random.normal(0,1,(num_examples,num_inputs)),dtype=torch.float)
	labels=true_w[0]*features[:,0]+true_w[1]*features[:,1]+true_b
	#加上一些非常小的波动
	labels+=torch.tensor(np.random.normal(0,0.01,size=labels.size()),dtype=torch.float)
	plt.plot(labels)
	plt.show()

	batch_size = 10
	dataset = Data.TensorDataset(features, labels)
	data_iter = Data.DataLoader(dataset, batch_size)
	for X,y in data_iter:
		print(X,y)
		break

#一元数据,便于展示
def prepare_data():
	num_inputs = 1
	num_examples = 1000
	true_w = 2
	true_b = 4.2
    #普通的线性函数：w*x + b
	features=torch.tensor(np.linspace(1, num_examples,num_examples),dtype=torch.float)
	labels=true_w*features[:]+true_b
	#加上一些非常小的波动
	labels+=torch.tensor(np.random.normal(0,1,size=labels.size()),dtype=torch.float)
	plt.plot(labels)
	plt.show()

	batch_size = 10
	dataset = Data.TensorDataset(features, labels) #特征和标签对应，即输入和输出
	data_iter = Data.DataLoader(dataset, batch_size)
	for X,y in data_iter:
		print(X,y)
		break

class LinearNet(nn.Module):
    def __init__(self,n_feature):
        super(LinearNet,self).__init__() 
        self.linear=nn.Linear(n_feature,1)

    #forward 定义前向传播
    def forward(self,x):
        y=self.linear(x)
        return y

net=LinearNet(num_inputs) 
init.normal_(net.linear.weight,mean=0,std=0.01)  
init.constant_(net.linear.bias,val=0) #同：net.linear.bias.data.fill_(0)
#这里的net.linear指的是我们在LinearNet里面定义的，有些人会用net[0]
#查看网络结构
print(net)
#查看所有可学习的参数
for param in net.parameters():
	print(param)

#损失函数
loss=nn.MSELoss()
#优化器
optimizer=optim.SGD(net.parameters(),lr=0.03)

#训练模型
for epoch in range(1, num_epochs + 1):
	for X,y in data_iter:
		output = net(X)
		l = loss(output, y.view(-1,1))
		optimizer.zero_grad()
		l.backward()
		optimizer.step()
	print('epoch %d, loss: %f'%(epoch, l.item()))
dense=net.linear
print('true_w:',dense.weight)
print('true_b:',dense.bias)

nn.LayerNorm(normalized_shape, eps=1e-05, elementwise_affine=True, device=None, dtype=None)

	arr = np.arange(0,3*5*5).reshape(3,5,5)
	arr = arr.astype(np.float32)
	arr = torch.tensor(arr)
	arr = arr.unsqueeze(0)
	print(arr.shape)# shape: [1,3,5,5]
	norm = nn.LayerNorm([3,5,5])
	res = norm(arr)
	print(res.shape) #shape: [1,3,5,5]

	arr = np.arange(0,3*5*5).reshape(3,5,5)
	arr = arr.astype(np.float32)
	arr = torch.tensor(arr)
	arr = arr.unsqueeze(0)
	print(arr.shape)# shape: [1,3,5,5]
	arr = arr.permute(0,2,3,1).contiguous()
	norm = nn.LayerNorm(3)
	res = norm(arr)
	print(res.shape) #shape: [1,5,5,3]
	res = res.permute(0,3,1,2)
	print(res)

nn.Embedding(num_embeddings-词典长度，embedding_dim-向量维度)

embedding = nn.Embedding(10,3)
	
input = tensor.LongTensor([\[1,2,3,4],[5,6,7,8]]) 

embedding(input) #shape: [2,4,3]

torch.nn.Conv1d(in_channels,       "输入的通道数"
                out_channels,      "卷积产生的通道数"
                kernel_size,       "卷积核的大小"
                stride,            "卷积的步幅。默认值：1"
                padding,           "添加到输入两侧的填充。默认值：0"
                dilation,          "内核元素之间的间距。默认值：1"
                groups,            "从输入通道到输出通道的阻塞连接数。默认值：1"
                bias,              "If True，向输出添加可学习的偏差。默认：True"
                padding_mode       "'zeros', 'reflect', 'replicate' 或 'circular'. 默认：'zeros'"
                )

import torch
import torch.nn as nn
input = torch.randn(1, 1, 5) #shape: [批大小， 数据的通道数， 数据长度]
conv = nn.Conv1d(in_channels=1, out_channels=1, kernel_size=3, stride=1, padding=0)
out = conv(input)

class Dropout(nn.Module):
	def __init__(self):
		super(Dropout, self).__init__()
		self.linear = nn.Linear(5,10)
		self.dropout = nn.Dropout(p=0.3)
	def forward(self, inputs):
		out = self.linear(inputs)
		out = self.dropout(out) #这里让上一层输出的30%的数据变为0
		return out

def run():
	net = Dropout()
	inputs = np.arange(0,5)
	inputs = torch.tensor(inputs, dtype=torch.float)
	inputs = inputs.repeat(1,1)

	print(inputs.shape)
	print(net(inputs))

#参数解释
#初始化
nn.RNN(
	input_size,  #输入的特征数
	hidden_size, #隐层维度
	num_layers = 1,  #层数
	batch_first = False, #把batch放在第一维度，即[batch, seq, feature]
	nolinearity = 'tanh,
	bias = 'True,
	dropout = 0,
	bidirectional = False,
)

#训练输入
def forward(self, x)
{}
# x 的 shape
# 1、对于没有batch，[seq_len, input_size]
# 2、对于 batch_first = False，[seq_len, batch_size, input_size]
# 3、对于 batch_first = True，[batch_size, seq_len, input_size]

#训练输出 shape
# 这里 d 是双向(是：2,否：1)
# 1、对于没有batch，[seq_len, d*hidden_size]
# 2、对于 batch_first = False，[seq_len, batch_size, d*hidden_size]
# 3、对于 batch_first = True，[batch_size, seq_len, d*hidden_size]
# 这里的 hidden_size 是隐层数量