How to solve ' CUDA out of memory. Tried to allocate xxx MiB' in pytorch?
I am trying to train a CNN in pytorch,but I meet some problems.
The RuntimeError:


  RuntimeError: CUDA out of memory. Tried to allocate 512.00 MiB (GPU 0;
  2.00 GiB total capacity; 584.97 MiB already allocated; 13.81 MiB free; 590.00 MiB reserved in total by PyTorch)


This is my code:

import os
import numpy as np
import cv2
import torch as t
import torch.nn as nn
import torchvision.transforms as transforms
from torch.utils.data import DataLoader,Dataset
import time
import matplotlib.pyplot as plt
%matplotlib inline
root_path='C:/Users/60960/Desktop/recet-task/course_LeeML20/course_LeeML20-datasets/hw3/food-11'
training_path=root_path+'/training'
testing_path=root_path+'/testing'
validation_path=root_path+'/validation'
def readfile(path,has_label):
    img_paths=sorted(os.listdir(path))
    x=np.zeros((len(img_paths),128,128,3),dtype=np.uint8)
    y=np.zeros((len(img_paths)),dtype=np.uint8)
    for i,file in enumerate(img_paths):
        img=cv2.imread(path+'/'+file)
        x[i,:,:]=cv2.resize(img,(128,128))
        if has_label:
            y[i]=int(file.split('_')[0])
    if has_label:
        return x,y
    else:
        return x
def show_img(img_from_cv2):
    b,g,r=cv2.split(img_from_cv2)
    img=cv2.merge([r,g,b])
    plt.imshow(img)
    plt.show()
x_train,y_train=readfile(training_path,True)
x_val,y_val=readfile(validation_path,True)
x_test=readfile(testing_path,False)
train_transform=transforms.Compose([
    transforms.ToPILImage(),
    transforms.RandomHorizontalFlip(),
    transforms.RandomRotation(15),
    transforms.ToTensor()
])
test_transform=transforms.Compose([
    transforms.ToPILImage(),
    transforms.ToTensor()
])
class ImgDataset(Dataset):
    def __init__(self,x,y=None,transform=None):
        self.x=x
        self.y=y
        if y is not None:
            self.y=t.LongTensor(y)
        self.transform=transform
    def __len__(self):
        return len(self.x)
    def __getitem__(self,idx):
        X=self.x[idx]
        if self.transform is not None:
            X=self.transform(X)
        if self.y is not None:
            Y=self.y[idx]
            return X,Y
        return X
batch_size=128
train_set=ImgDataset(x_train,y_train,transform=train_transform)
val_set=ImgDataset(x_val,y_val,transform=test_transform)
train_loader=DataLoader(train_set,batch_size=batch_size,shuffle=True)
val_loader=DataLoader(val_set,batch_size=batch_size,shuffle=False)
class Classifier(nn.Module):
    def __init__(self):
        super(Classifier,self).__init__()
        self.cnn=nn.Sequential(
            nn.Conv2d(3,64,3,1,1),
            nn.BatchNorm2d(64),
            nn.ReLU(),
            nn.MaxPool2d(2,2,0),

            nn.Conv2d(64,128,3,1,1),
            nn.BatchNorm2d(128),
            nn.ReLU(),
            nn.MaxPool2d(2,2,0),

            nn.Conv2d(128,256,3,1,1),
            nn.BatchNorm2d(256),
            nn.ReLU(),
            nn.MaxPool2d(2,2,0),

            nn.Conv2d(256,512,3,1,1),
            nn.BatchNorm2d(512),
            nn.ReLU(),
            nn.MaxPool2d(2,2,0),

            nn.Conv2d(512,512,3,1,1),
            nn.BatchNorm2d(512),
            nn.ReLU(),
            nn.MaxPool2d(2,2,0)
        )
        self.fc=nn.Sequential(
            nn.Linear(512*4*4,1024),
            nn.ReLU(),
            nn.Linear(1024,512),
            nn.ReLU(),
            nn.Linear(512,11)
        )
    def forward(self,x):
        out=self.cnn(x)
        out=out.view(out.size()[0],-1)
        return self.fc(out)
model=Classifier().cuda()
loss_fn=nn.CrossEntropyLoss()
optim=t.optim.Adam(model.parameters(),lr=0.001)
epochs=30
for epoch in range(epochs):
    epoch_start_time=time.time()
    train_acc=0.0
    train_loss=0.0
    val_acc=0.0
    val_loss=0.0
    model.train()
    for i,data in enumerate(train_loader):
        optim.zero_grad()
        train_pred=model(data[0].cuda())
        batch_loss=loss_fn(train_pred,data[1].cuda())
        batch_loss.backward()
        optim.step()
        train_acc+=np.sum(np.argmax(train_pred.cpu().data.numpy(),axis=1)==data[1].numpy())
        train_loss+=batch_loss.item()
    model.eval()
    with t.no_grad():
        for i,data in enumerate(val_loader):
            val_pred=model(data[0].cuda())
            batch_loss=loss_fn(val_pred,data[1].cuda())
            val_acc+=np.sum(np.argmax(val_pred.cpu().data.numpy(),axis=1)==data[1].numpy())
            val_loss+=batch_loss.item()
        print('[%03d/%03d] %2.2f sec(s) Train Acc: %3.6f Loss: %3.6f | Val Acc: %3.6f loss: %3.6f' % (epoch + 1, epochs, time.time()-epoch_start_time,train_acc/train_set.__len__(), train_loss/train_set.__len__(), val_acc/val_set.__len__(), val_loss/val_set.__len__()))
x_train_val=np.concatenate((x_train,x_val),axis=0)
y_train_val=np.concatenate((y_train,y_val),axis=0)
train_val_set=ImgDataset(x_train_val,x_train_val,train_transform)
train_val_loader=DataLoader(train_val_set,batch_size=batch_size,shuffle=True)
model_final=Classifier().cuda()
loss_fn=nn.CrossEntropy()
optim=t.optim.Adam(model_final.parameters(),lr=0.001)
epochs=30
for epoch in range(epochs):
    epoch_start_time=time.time()
    train_acc=0.0
    train_loss=0.0
    model_final.train()
    for i,data in enumerate(train_val_loader):
        optim.zero_grad()
        train_pred=model_final(data[0].cuda())
        batch_loss=loss_fn(train_pred,data[1].cuda())
        batch_loss.backward()
        optim.step()
        train_acc+=np.sum(np.argmax(train_pred.cpu().data.numpy(),axis=1)==data[1].numpy())
        train_loss+=batch_loss.item()
    print('[%03d/%03d] %2.2f sec(s) Train Acc: %3.6f Loss: %3.6f' % (epoch + 1, epochs, time.time()-epoch_start_time,train_acc/train_val_set.__len__(), train_loss/train_val_set.__len__()))
test_set=ImgDataset(x_test,transform=test_transform)
test_loader=DataLoader(test_set,batch_size=batch_size,shuffle=False)
model_final.eval()
prediction=[]
with t.no_grad():
    for i,data in enumerate(test_loader):
        test_pred=model_final(data.cuda())
        test_label=np.argmax(test_pred.cpu().data.numpy(),axis=1)
        for y in test_label:
            prediction.append(y)
with open('predict.csv','w') as f:
    f.write('Id,Category\n')
    for i,y in enumerate(prediction):
        f.write('{},{}\n,'.format(i,y))


Pytorch version is 1.4.0, opencv2 version is 4.2.0.
The training dataset are pictures like these:training set

The error happens at this line:

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
&lt;ipython-input-1-770be67177f4&gt; in &lt;module&gt;
    119     for i,data in enumerate(train_loader):
    120         optim.zero_grad()
--&gt; 121         train_pred=model(data[0].cuda())
    122         batch_loss=loss_fn(train_pred,data[1].cuda())
    123         batch_loss.backward()


I have already installed:
some information.
GPU utilization is low,close to zero:
GPU utilization.
Error message says:


  RuntimeError: CUDA out of memory.  Tried to allocate 512.00 MiB.


So I want to know how to allocate more memory.
What's more, I have tried to reduce the batch size to 1, but this doesn't work.
HELP!!!

Before reducing the batch size check the status of GPU memory :slight_smile:
nvidia-smi
Then check which process is eating up the memory choose PID and kill :boom: that process with
sudo kill -9 PID
or
sudo fuser -v /dev/nvidia*
sudo kill -9 PID
