SSD代码笔记 + EifficientNet backbone 练习
ssd代码完全ok了，然后用最近性能和速度都非常牛的Eifficient Net做backbone设计了自己的TinySSD网络，没有去调参，所以网络并没有很好的收敛，之后我会调一调，实际去应用。
torch.clamp
torch.clamp(input, min, max, out=None) → Tensor
就是clip的功能
eg:
>>> a = torch.randn(4)
>>> a
tensor([-1.7120, 0.1734, -0.0478, -0.0922])
>>> torch.clamp(a, min=-0.5, max=0.5)
tensor([-0.5000, 0.1734, -0.0478, -0.0922])计算iou
交集除以并集，首先要算面积，面积就是给定两个点坐标求宽高乘积即可。
交集面积就是两个框离原点最远的左上角点与离原点最近的右下角点组成区域的面积。
def area_of(left_top,right_bottom):# (num_boxes,2),(num_boxes,2)
hw = torch.clamp(right_bottom-left_top,0.0) # (num_boxes,2)
# 这里做clip的原因是如果框不重叠的化，如果不clip算出来就是负值，有了clip就是0
return hw[...,0] * hw[...,1]
def iou_of(boxes0,boxes1,eps = 1e-5):# (N,4) and (1,4) or (N,4)
# 注意这里其实boxes0和boxes1和size其实是不一样的，所以size较少的那个会broadcast到较大的那个然后在做max和min操作。
overlap_left_top = torch.max(boxes0[...,:2],boxes1[...:2])# 左上角点最远的
overlap_right_bottom = torch.min(boxes0[...,2:],boxes1[...,2:]) # 右下角点最近的
area0 = area_of(boxes0[...,:2],boxes0[...,2:]) # 左上角和右下角点计算面积
area1 = area_of(boxes1[...,:2],boxes1[...,2:]) # predict box的面积
overlap_area = area_of(overlap_left_top,over_right_bottom) # 并集面积
return overlap_area / (area0 + area1 - overlap_area + eps)
生成priorbox
这里生成坐标的方法是真学到了，product构造映射。实际上featur map上每个点都是加了0.5作为中心，然后除以ratio，这里ratio一般和feature map 的size是不一样的，取决于网络设计，我这里用的刚好一样。ratio就是对应到原图有多少个滑窗。后面考虑了其他尺度的anchor。
#有的注释是原来代码里的，有的英文注释是我加的。
class PriorBox(nn.Module):
def __init__(self):
super(PriorBox, self).__init__()
self.image_size = 512
self.feature_maps = [16,8,4,2,1]
self.min_sizes = [30,60,111,162,213]
self.max_sizes = [60,111,162,213,512]
self.strides = [32,64,128,256,512]
self.aspect_ratios = [[2], [2, 3], [2, 3], [2], [2]]
self.clip = True
def forward(self):
"""Generate SSD Prior Boxes.
It returns the center, height and width of the priors. The values are relative to the image size
Returns:
priors (num_priors, 4): The prior boxes represented as [[center_x, center_y, w, h]]. All the values
are relative to the image size.
"""
priors = []
for k, f in enumerate(self.feature_maps): # every size of feature map
scale = self.image_size / self.strides[k] # how many boxes (not anchor) in a row in raw img
# 512 / 32 = 16
for i, j in product(range(f), repeat=2): # xy generator in feature map
# unit center x,y
cx = (j + 0.5) / scale # see as blocks and xy in center of it
cy = (i + 0.5) / scale # 15,15 -> 15.5,15.5 -> 15.5/16,15.5/16 which means the xy in center of feature map
# small sized square box
size = self.min_sizes[k] # min size
h = w = size / self.image_size # small size
priors.append([cx, cy, w, h]) # the small size one
# big sized square box
size = sqrt(self.min_sizes[k] * self.max_sizes[k]) # the same as small one
h = w = size / self.image_size
priors.append([cx, cy, w, h])
# change h/w ratio of the small sized box
# considering the w/ratio , w*ratio , h/ratio and h * ratio
size = self.min_sizes[k]
h = w = size / self.image_size
for ratio in self.aspect_ratios[k]:
ratio = sqrt(ratio)
priors.append([cx, cy, w * ratio, h / ratio])
priors.append([cx, cy, w / ratio, h * ratio])
priors = torch.Tensor(priors)
if self.clip:
priors.clamp_(max=1, min=0)
return priorspriorbox的分配
很好的利用了broadcast机制，计算每个iou，然后得到target与所有prior重叠度最高的匹配，以及prior与target重叠度最高的匹配，然后通过阈值滤去。
def assign_priors(gt_boxes, gt_labels, corner_form_priors,
iou_threshold):
"""Assign ground truth boxes and targets to priors.
Args:
gt_boxes (num_targets, 4): ground truth boxes.
gt_labels (num_targets): labels of targets.
priors (num_priors, 4): corner form priors
Returns:
boxes (num_priors, 4): real values for priors.
labels (num_priros): labels for priors.
"""
# size: num_priors x num_targets
ious = iou_of(gt_boxes.unsqueeze(0), corner_form_priors.unsqueeze(1))
# size: num_priors
best_target_per_prior, best_target_per_prior_index = ious.max(1) # 每个prior的iou最大的值以及在target里的索引
# size: num_targets
best_prior_per_target, best_prior_per_target_index = ious.max(0) # 每个target与所有prior的iou最大值以及在priors里的索引
for target_index, prior_index in enumerate(best_prior_per_target_index):
best_target_per_prior_index[prior_index] = target_index # 让每个Prior对应iou最大的target (0,0,1,2,3)
# 2.0 is used to make sure every target has a prior assigned
best_target_per_prior.index_fill_(0, best_prior_per_target_index, 2) # dim = 0 ,value = 2,只要重叠的iou最大，就认为其重叠度是2
# size: num_priors
labels = gt_labels[best_target_per_prior_index] # num_priors，先按照iou最大分
labels[best_target_per_prior < iou_threshold] = 0 # the backgournd id，小于阈值的认为是背景，有的iou尽管最大但是其iou还是很小，所以也需要滤去
boxes = gt_boxes[best_target_per_prior_index] # 直接给box
return boxes, labelshard_negative_mining
通过给出mask考虑算哪些loss不算哪些loss，因为负样本实在太多了，所以这是一个方法。
def hard_negative_mining(loss, labels, neg_pos_ratio):
"""
It used to suppress the presence of a large number of negative prediction.
It works on image level not batch level.
For any example/image, it keeps all the positive predictions and
cut the number of negative predictions to make sure the ratio
between the negative examples and positive examples is no more
the given ratio for an image.
Args:
loss (N, num_priors): the loss for each example.
labels (N, num_priors): the labels.
neg_pos_ratio: the ratio between the negative examples and positive examples.
"""
pos_mask = labels > 0
num_pos = pos_mask.long().sum(dim=1, keepdim=True)
num_neg = num_pos * neg_pos_ratio
loss[pos_mask] = -math.inf
_, indexes = loss.sort(dim=1, descending=True)
_, orders = indexes.sort(dim=1)
neg_mask = orders < num_neg
return pos_mask | neg_maskLoss Function
bbox用smotth L1 loss，交叉熵分类loss。
class MultiBoxLoss(nn.Module):
def __init__(self, neg_pos_ratio):
"""Implement SSD MultiBox Loss.
Basically, MultiBox loss combines classification loss
and Smooth L1 regression loss.
"""
super(MultiBoxLoss, self).__init__()
self.neg_pos_ratio = neg_pos_ratio
def forward(self, confidence, predicted_locations, labels, gt_locations):
"""Compute classification loss and smooth l1 loss.
Args:
confidence (batch_size, num_priors, num_classes): class predictions.
predicted_locations (batch_size, num_priors, 4): predicted locations.
labels (batch_size, num_priors): real labels of all the priors.
gt_locations (batch_size, num_priors, 4): real boxes corresponding all the priors.
"""
num_classes = confidence.size(2)
with torch.no_grad():
# derived from cross_entropy=sum(log(p))
loss = -F.log_softmax(confidence, dim=2)[:, :, 0]
mask = box_utils.hard_negative_mining(loss, labels, self.neg_pos_ratio)
confidence = confidence[mask, :]
#print(confidence.view(-1, num_classes))
#print(labels[mask])
classification_loss = F.cross_entropy(confidence.view(-1, num_classes), labels[mask], reduction='sum')
pos_mask = labels > 0
predicted_locations = predicted_locations[pos_mask, :].view(-1, 4)
gt_locations = gt_locations[pos_mask, :].view(-1, 4)
smooth_l1_loss = F.smooth_l1_loss(predicted_locations, gt_locations, reduction='sum')
num_pos = gt_locations.size(0)
return smooth_l1_loss / num_pos, classification_loss / num_posModel
我看网络模型搜索得到的Eifficient Net性能和速度都是最优，直接拿来做backbone，但是调参还没调好，只是直接用其输出然后再加5层卷积层分别做特征金字塔，感觉感受野可能太大了，网络收敛性能不是很好，后面会调好参的，但是还是可以跑的。
Eifficient Net Model
import torch
from torch import nn
from torch.nn import functional as F
from .utils import (
relu_fn,
round_filters,
round_repeats,
drop_connect,
Conv2dSamePadding,
get_model_params,
efficientnet_params,
load_pretrained_weights,
)
class MBConvBlock(nn.Module):
"""
Mobile Inverted Residual Bottleneck Block
Args:
block_args (namedtuple): BlockArgs, see above
global_params (namedtuple): GlobalParam, see above
Attributes:
has_se (bool): Whether the block contains a Squeeze and Excitation layer.
"""
def __init__(self, block_args, global_params):
super().__init__()
self._block_args = block_args
self._bn_mom = 1 - global_params.batch_norm_momentum
self._bn_eps = global_params.batch_norm_epsilon
self.has_se = (self._block_args.se_ratio is not None) and (0 < self._block_args.se_ratio <= 1)
self.id_skip = block_args.id_skip # skip connection and drop connect
# Expansion phase
inp = self._block_args.input_filters # number of input channels
oup = self._block_args.input_filters * self._block_args.expand_ratio # number of output channels
if self._block_args.expand_ratio != 1:
self._expand_conv = Conv2dSamePadding(in_channels=inp, out_channels=oup, kernel_size=1, bias=False)
self._bn0 = nn.BatchNorm2d(num_features=oup, momentum=self._bn_mom, eps=self._bn_eps)
# Depthwise convolution phase
k = self._block_args.kernel_size
s = self._block_args.stride
self._depthwise_conv = Conv2dSamePadding(
in_channels=oup, out_channels=oup, groups=oup, # groups makes it depthwise
kernel_size=k, stride=s, bias=False)
self._bn1 = nn.BatchNorm2d(num_features=oup, momentum=self._bn_mom, eps=self._bn_eps)
# Squeeze and Excitation layer, if desired
if self.has_se:
num_squeezed_channels = max(1, int(self._block_args.input_filters * self._block_args.se_ratio))
self._se_reduce = Conv2dSamePadding(in_channels=oup, out_channels=num_squeezed_channels, kernel_size=1)
self._se_expand = Conv2dSamePadding(in_channels=num_squeezed_channels, out_channels=oup, kernel_size=1)
# Output phase
final_oup = self._block_args.output_filters
self._project_conv = Conv2dSamePadding(in_channels=oup, out_channels=final_oup, kernel_size=1, bias=False)
self._bn2 = nn.BatchNorm2d(num_features=final_oup, momentum=self._bn_mom, eps=self._bn_eps)
def forward(self, inputs, drop_connect_rate=None):
"""
:param inputs: input tensor
:param drop_connect_rate: drop connect rate (float, between 0 and 1)
:return: output of block
"""
# Expansion and Depthwise Convolution
x = inputs
if self._block_args.expand_ratio != 1:
x = relu_fn(self._bn0(self._expand_conv(inputs)))
x = relu_fn(self._bn1(self._depthwise_conv(x)))
# Squeeze and Excitation
if self.has_se:
x_squeezed = F.adaptive_avg_pool2d(x, 1)
x_squeezed = self._se_expand(relu_fn(self._se_reduce(x_squeezed)))
x = torch.sigmoid(x_squeezed) * x
x = self._bn2(self._project_conv(x))
# Skip connection and drop connect
input_filters, output_filters = self._block_args.input_filters, self._block_args.output_filters
if self.id_skip and self._block_args.stride == 1 and input_filters == output_filters:
if drop_connect_rate:
x = drop_connect(x, p=drop_connect_rate, training=self.training)
x = x + inputs # skip connection
return x
class EfficientNet(nn.Module):
"""
An EfficientNet model. Most easily loaded with the .from_name or .from_pretrained methods
Args:
blocks_args (list): A list of BlockArgs to construct blocks
global_params (namedtuple): A set of GlobalParams shared between blocks
Example:
model = EfficientNet.from_pretrained('efficientnet-b0')
"""
def __init__(self, blocks_args=None, global_params=None):
super().__init__()
assert isinstance(blocks_args, list), 'blocks_args should be a list'
assert len(blocks_args) > 0, 'block args must be greater than 0'
self._global_params = global_params
self._blocks_args = blocks_args
# Batch norm parameters
bn_mom = 1 - self._global_params.batch_norm_momentum
bn_eps = self._global_params.batch_norm_epsilon
# Stem
in_channels = 3 # rgb
out_channels = round_filters(32, self._global_params) # number of output channels
self._conv_stem = Conv2dSamePadding(in_channels, out_channels, kernel_size=3, stride=2, bias=False)
self._bn0 = nn.BatchNorm2d(num_features=out_channels, momentum=bn_mom, eps=bn_eps)
# Build blocks
self._blocks = nn.ModuleList([])
for block_args in self._blocks_args:
# Update block input and output filters based on depth multiplier.
block_args = block_args._replace(
input_filters=round_filters(block_args.input_filters, self._global_params),
output_filters=round_filters(block_args.output_filters, self._global_params),
num_repeat=round_repeats(block_args.num_repeat, self._global_params)
)
# The first block needs to take care of stride and filter size increase.
self._blocks.append(MBConvBlock(block_args, self._global_params))
if block_args.num_repeat > 1:
block_args = block_args._replace(input_filters=block_args.output_filters, stride=1)
for _ in range(block_args.num_repeat - 1):
self._blocks.append(MBConvBlock(block_args, self._global_params))
# Head
in_channels = block_args.output_filters # output of final block
out_channels = round_filters(1280, self._global_params)
self._conv_head = Conv2dSamePadding(in_channels, out_channels, kernel_size=1, bias=False)
self._bn1 = nn.BatchNorm2d(num_features=out_channels, momentum=bn_mom, eps=bn_eps)
# Final linear layer
self._dropout = self._global_params.dropout_rate
self._fc = nn.Linear(out_channels, self._global_params.num_classes)
def extract_features(self, inputs):
""" Returns output of the final convolution layer """
# Stem
x = relu_fn(self._bn0(self._conv_stem(inputs)))
# Blocks
for idx, block in enumerate(self._blocks):
drop_connect_rate = self._global_params.drop_connect_rate
if drop_connect_rate:
drop_connect_rate *= float(idx) / len(self._blocks)
x = block(x) # , drop_connect_rate) # see https://github.com/tensorflow/tpu/issues/381
return x
def forward(self, inputs):
""" Calls extract_features to extract features, applies final linear layer, and returns logits. """
# Convolution layers
x = self.extract_features(inputs)
# Head
x = relu_fn(self._bn1(self._conv_head(x)))
x = F.adaptive_avg_pool2d(x, 1).squeeze(-1).squeeze(-1)
if self._dropout:
x = F.dropout(x, p=self._dropout, training=self.training)
x = self._fc(x)
return x
@classmethod
def from_name(cls, model_name, override_params=None):
cls._check_model_name_is_valid(model_name)
blocks_args, global_params = get_model_params(model_name, override_params)
return EfficientNet(blocks_args, global_params)
@classmethod
def from_pretrained(cls, model_name):
model = EfficientNet.from_name(model_name)
load_pretrained_weights(model, model_name)
return model
@classmethod
def get_image_size(cls, model_name):
cls._check_model_name_is_valid(model_name)
_, _, res, _ = efficientnet_params(model_name)
return res
@classmethod
def _check_model_name_is_valid(cls, model_name, also_need_pretrained_weights=False):
""" Validates model name. None that pretrained weights are only available for
the first four models (efficientnet-b{i} for i in 0,1,2,3) at the moment. """
num_models = 4 if also_need_pretrained_weights else 8
valid_models = ['efficientnet_b'+str(i) for i in range(num_models)]
if model_name.replace('-','_') not in valid_models:
raise ValueError('model_name should be one of: ' + ', '.join(valid_models))
My TinySSD Model
'''
@Descripttion: This is Aoru Xue's demo,which is only for reference
@version:
@Author: Aoru Xue
@Date: 2019-06-14 00:42:10
@LastEditors: Aoru Xue
@LastEditTime: 2019-06-15 12:41:47
'''
import torch
from torch import nn
from efficientnet_pytorch import EfficientNet
from prior_box import PriorBox
from torchsummary import summary
import torch.nn.functional as F
from box_utils import *
def predict_bbox(in_features,num_anchors):
return
def predict_class(in_features,num_anchors, num_classes):
return nn.Conv2d(in_features,(num_classes + 1) * num_anchors,kernel_size = 3,padding = 1)
class TinySSD(nn.Module):
def __init__(self,classes = 10):
super(TinySSD,self).__init__()
self.num_classes = classes
self.basenet = EfficientNet.from_pretrained('efficientnet-b0')
self.predict_bbox = [
nn.Conv2d(320,num_anchors * 4,kernel_size = 3,padding =1)
for num_anchors in [4,6,6,4,4]
]
for idx,num_anchors in enumerate([4,6,6,4,4]):
setattr(self,"predict_bbox_{}".format(idx + 1),nn.Conv2d(
320,num_anchors * 4,kernel_size = 3,padding = 1
))
setattr(self,"predict_class_{}".format(idx + 1),nn.Conv2d(
320,3 * num_anchors,kernel_size = 3,padding =1
))
for idx,k in enumerate([[320,320],[320,320],[320,320]]):
setattr(self,"feature_{}".format(idx + 2),nn.Sequential(
nn.Conv2d(k[0],k[1],kernel_size = 3,padding =1),
nn.BatchNorm2d(k[1]),
nn.ReLU(),
nn.Conv2d(k[1],k[1],kernel_size = 3,padding =1),
nn.BatchNorm2d(k[1]),
nn.ReLU(),
nn.MaxPool2d(2)
))
def forward(self,x):
x = self.basenet.extract_features(x)
feature_1 = x
feature_2 = self.feature_2(x)
feature_3 = self.feature_3(feature_2)
feature_4 = self.feature_4(feature_3)
feature_5 = F.max_pool2d(feature_4,kernel_size = 2)
'''
(2,4*4,16,16)
(2,4*6,8,8)
(2,4*6,4,4),
(2,4*4,2,2),
(2,4*4,1,1)
-> 每个 anchor 中心，连续4个值代表x y w h
'''
bbox_1 = torch.transpose(self.predict_bbox_1(feature_1),1,3).contiguous().flatten(start_dim = 1)
bbox_2 = torch.transpose(self.predict_bbox_2(feature_2),1,3).contiguous().flatten(start_dim = 1)
bbox_3 = torch.transpose(self.predict_bbox_3(feature_3),1,3).contiguous().flatten(start_dim = 1)
bbox_4 = torch.transpose(self.predict_bbox_4(feature_4),1,3).contiguous().flatten(start_dim = 1)
bbox_5 = torch.transpose(self.predict_bbox_5(feature_5),1,3).contiguous().flatten(start_dim = 1)
pred_bbox = torch.cat([bbox_1,bbox_2,bbox_3,bbox_4,bbox_5],dim = 1)
'''
(2,anchors*classes,16,16)
-> 每隔anchor个代表一个anchor的预测
'''
class_1 = torch.transpose(self.predict_class_1(feature_1),1,3).contiguous().flatten(start_dim = 1)
class_2 = torch.transpose(self.predict_class_2(feature_2),1,3).contiguous().flatten(start_dim = 1)
class_3 = torch.transpose(self.predict_class_3(feature_3),1,3).contiguous().flatten(start_dim = 1)
class_4 = torch.transpose(self.predict_class_4(feature_4),1,3).contiguous().flatten(start_dim = 1)
class_5 = torch.transpose(self.predict_class_5(feature_5),1,3).contiguous().flatten(start_dim = 1)
pred_class = torch.cat([class_1,class_2,class_3,class_4,class_5],dim = 1)
return [pred_bbox.view(x.size(0),-1,4),pred_class.view(x.size(0),-1,3)] # (2,6096) (2,0000)
if __name__ == "__main__":
net = TinySSD(10)
prior = PriorBox()
print(len(prior()))
gt_prior = assign_priors(torch.Tensor([[0,0,10/512,10/512],[55/512,55/512,30/512,30/512]]),torch.Tensor([1,2,5]),prior(),0.5)
print(gt_prior[1])
#x = torch.randn(2,3,512,512)
#out = net(x)
#print(prior()[:200,:])
#print(out[0].size())
#print(out[1].size())
#summary(net,(3,512,512),device="cpu")
dataset
'''
@Descripttion: This is Aoru Xue's demo,which is only for reference
@version:
@Author: Aoru Xue
@Date: 2019-06-15 12:48:09
@LastEditors: Aoru Xue
@LastEditTime: 2019-06-15 12:48:09
'''
import torch
import torch.nn
from torch.utils.data import Dataset
from PIL import Image
from prior_box import PriorBox
from box_utils import *
class Mydataset(Dataset):
def __init__(self,img_list_txt = "./dataset/train.txt",transform = None):
self.dataset = []
with open(img_list_txt,"r") as f:
for line in f:
line = line.replace("\n","")
gt_txt_name = line.replace(".jpg",".txt")
gt_bbox = []
gt_class = []
with open(gt_txt_name,"r") as ff:
for l in ff:
l = l.replace("\n","")
ll = l.split(" ")
ll = list(map(lambda x:float(x),ll))
ll[-1] = int(ll[-1])
gt_bbox.append(ll[:-1])
gt_class.append(ll[-1])
if len(gt_bbox):
self.dataset.append({
"image_path": line, # img path
"gt_bbox": gt_bbox, # (x,y,w,h) and class
"gt_class":gt_class
})
prior = PriorBox()
self.priors = prior()
self.transform = transform
def __len__(self):
return len(self.dataset)
def __getitem__(self,idx):
data = self.dataset[idx]
img = Image.open(data["image_path"])
gt_bboxes = torch.tensor(data["gt_bbox"])
gt_classes = torch.tensor(data["gt_class"])
if self.transform:
img = self.transform(img)
gt_bboxes,gt_classes = assign_priors(gt_bboxes,gt_classes,self.priors,0.5)
return [img,gt_bboxes,gt_classes]训练
'''
@Descripttion: This is Aoru Xue's demo,which is only for reference
@version:
@Author: Aoru Xue
@Date: 2019-06-15 12:56:39
@LastEditors: Aoru Xue
@LastEditTime: 2019-06-15 12:56:39
'''
import torch
import torchvision
from TinySSD import TinySSD
from dataset import Mydataset
from torchvision import transforms
from torch.utils.data import DataLoader
from multibox_loss import MultiBoxLoss
import torch.optim as optim
def train(dataloader,net,loss_fn,optimizer,epochs = 200):
for epoch in range(epochs):
running_loss_bbox = 0.
running_loss_class = 0.
for img,gt_bbox,gt_class in dataloader:
img = img.cuda()
gt_bbox = gt_bbox.cuda()
gt_class = gt_class.cuda()
optimizer.zero_grad()
pred_bbox,pred_class = net(img)
#boxes,labels = assign_priors()
#print(gt_bbox.size(),gt_class.size())
#print(pred_bbox.size(),pred_class.size())
loss = loss_fn(pred_class,pred_bbox,gt_class,gt_bbox)
optimizer.step()
#print(pred_bbox.size(),pred_class.size())
running_loss_bbox += loss[0].cpu().item()
running_loss_class += loss[1].cpu().item()
print("epoch: {},bbox loss:{:.8f} , class loss:{:.8f}".format(epoch + 1,loss[0].cpu().item(),loss[1].cpu().item()))
print("*" * 20)
print("average bbox loss: {:.8f}; average class loss: {:.8f}".format(running_loss_bbox/len(dataloader),running_loss_class/len(dataloader)))
if epoch % 5 == 0:
torch.save(net.state_dict(),"./ckpt/{}.pkl".format(epoch))
if __name__ == "__main__":
net = TinySSD()
net.cuda()
loss_fn = MultiBoxLoss(0.5)
transform = transforms.Compose([
transforms.Resize((512,512)),
transforms.ToTensor(),
transforms.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225])
]
)
optm = optim.SGD(net.parameters(),lr = 0.001,momentum = 0.9)
dtset = Mydataset(transform = transform)
dataloader = DataLoader(dtset,batch_size = 4,shuffle = True)
train(dataloader,net,loss_fn,optm)