jwfromm opened a new issue #8978: Very Low Accuracy When Using Pretrained Model
URL: https://github.com/apache/incubator-mxnet/issues/8978
 
 
   ## Description
   Pretrained models dont seem to be working well with gluon, specifically 
datasets build with Dataloader and ImageRecords or ImageFolders.
   
   As an example, here I load the ImageNet validation dataset and feed it into 
alexnet downloaded from gluon model zoo
   
   ```
   ctx = mx.gpu()
   batch_size = 64
   def transformer(data, label):
       data = mx.image.imresize(data, 224, 224)
       data = mx.nd.transpose(data, (2,0,1))
       data = data.astype(np.float32)
       return data/255, label
   
   test_data = 
gluon.data.DataLoader(gluon.data.vision.ImageFolderDataset(root="/data2/imagenet/val/",
 transform=transformer),
                                         batch_size, shuffle=False)
   
   model = gluon.model_zoo.vision.alexnet(pretrained=True, ctx=ctx)
   
   def evaluate_accuracy(data_iterator, net):
       acc = mx.metric.Accuracy()
       for d, l in data_iterator:
           data = d.as_in_context(ctx)
           label = l.as_in_context(ctx)
           output = net(data)
           predictions = nd.argmax(output, axis=1)
           acc.update(preds=predictions, labels=label)
       return acc.get()[1]
   
   evaluate_accuracy(test_data, model, ctx=ctx)
   [0.12393999999999999]
   ```
   
   The 12% accuracy shows the issue is probably that the transforms used to 
train the model dont exactly align with the transforms presented in the Gluon 
tutorial. It would be nice if an example showing how to properly do this using 
the new gluon functions were added.
   
   ## Environment info (Required)
   Python 3.6

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