Load a single image in a pretrained pytorch net: Always get 0 of predict

alejo30: <pre><code class="lang-auto">from fastai.vision import *
from torchvision import datasets, transforms, models
import numpy as np
import torch
from torch import nn
from torch import optim
import torch.nn.functional as F
from torch.autograd import Variable

def conv_block(ni, nf, size=3, stride=1):
    for_pad = lambda s: s if s &gt; 2 else 3
    return nn.Sequential(
        nn.Conv2d(ni, nf, kernel_size=size, stride=stride,
                  padding=(for_pad(size) - 1)//2, bias=False), 
        nn.BatchNorm2d(nf),
        nn.LeakyReLU(negative_slope=0.1, inplace=True)  
    )

def triple_conv(ni, nf):
    return nn.Sequential(
        conv_block(ni, nf),
        conv_block(nf, ni, size=1),  
        conv_block(ni, nf)
    )

def maxpooling():
    return nn.MaxPool2d(2, stride=2)

model = nn.Sequential(
    conv_block(3, 8),
    maxpooling(),
    conv_block(8, 16),
    maxpooling(),
    triple_conv(16, 32),
    maxpooling(),
    triple_conv(32, 64),
    maxpooling(),
    triple_conv(64, 128),
    maxpooling(),
    triple_conv(128, 256),
    conv_block(256, 128, size=1),
    conv_block(128, 256),
    conv_layer(256, 2),
    Flatten(),
    nn.Linear(338, 2)
)

pretrained_dict =  torch.load('trained_modelCov-N.pth',map_location=torch.device('cpu'))
model_dict = model.state_dict()

# 1. filter out unnecessary keys
pretrained_dict = {k: v for k, v in pretrained_dict.items() if k in model_dict}
# 2. overwrite entries in the existing state dict
model_dict.update(pretrained_dict) 
# 3. load the new state dict
model.load_state_dict(model_dict)
model.eval()

data_dir = '/content/gdrive/My Drive/DCN(data)/Train/'

test_transforms = transforms.Compose([  
 transforms.Resize((256, 256)),         
 transforms.ToTensor(),                 
 #transforms.Normalize(                 
 #mean=[0.485, 0.456, 0.406],           
 #std=[0.229, 0.224, 0.225])
 ])

def predict_image(image):
    image_tensor = test_transforms(image).float()
    image_tensor = image_tensor.unsqueeze_(0)
    input = Variable(image_tensor)
    input = input.to(device)
    output = model(input)
    index = output.data.cpu().numpy().argmax()
    return index  

def get_random_images(num):
    data = datasets.ImageFolder(data_dir, transform=test_transforms)
    classes = data.classes
    indices = list(range(len(data)))
    np.random.shuffle(indices)
    idx = indices[:num]
    from torch.utils.data.sampler import SubsetRandomSampler
    sampler = SubsetRandomSampler(idx)
    loader = torch.utils.data.DataLoader(data, sampler=sampler, batch_size=num)
    dataiter = iter(loader)
    images, labels = dataiter.next()
    return images, labels

data = datasets.ImageFolder(data_dir, transform=test_transforms)
classes=data.classes
indices=list(range(len(data)))

to_pil = transforms.ToPILImage()
images, labels = get_random_images(10)
fig=plt.figure(figsize=(40,50))
for ii in range(len(images)):
    image = to_pil(images[ii])
    index = predict_image(image)
    sub = fig.add_subplot(1, len(images), ii+1)
    res = int(labels[ii]) == index
    sub.set_title(str(classes[index]) + ":" + str(res))
    print(index)
    plt.axis('off')
    plt.imshow(image,cmap='binary')
plt.show()
</code></pre>
<p>Always obtain predict 0 in all images</p>

ptrblck: <p>Was this model predicting other classes before?<br>
If so, how many classes were used during training and validation and how was the training and validation accuracy, repectively?<br>
Were you working with an imbalanced dataset? If so, could you post the class distribution?</p>
<p>PS: <code>Variables</code> are deprecated since PyTorch <code>0.4</code> and you should not use the <code>.data</code> attribute, as it might have unwanted side effects.</p>