Vascellari asked . 2022-11-11

Why are the results of forward and predict very different in deep learning?

When I use the "dlnetwork" type deep neural network model to make predictions, the results of the two functions are very different, except that using the predict function will freeze the batchNormalizationLayer and dropout layers.While forward does not freeze the parameters, he is the forward transfer function used in the training phase.
 
 

predict-very

predict-very

From the two pictures above, there are orders of magnitude difference in the output of the previous 10 results. Where does the problem appear?

AI, Data Science, and Statistics , Deep Learning Toolbox , Deep Learning with Images

Expert Answer

Kshitij Singh answered . 2024-05-19 08:14:21

I ran into this exact problem, and I think I found a solution, I'll discover it when my model finishes training...
 
As others said before, the problem occurs because batchNorms behave differently in forward() and predict(). But there is still a problem here: if you trained your model (forward), it should have converged to a solution that works well in inference (predict), but it doesn't. Something is wrong in the training too.
 
What is wrong is that batchNorms don't update parameters the same way as other layers through (adam/rmsprop/sgdm)update functions. They update through the State property of the dlnetwork object. Consider the code:
 
[gradients,loss] = dlfeval(@modelGradients,dlnet,dlX,Ylabel);
[dlnet,otherOutputs]=rmspropupdate(dlnet,gradients,otherInputs);
function [gradients,loss] = modelGradients(dlnet,dlX,Ylabel)
Y=forward(dlnet,dlX);
loss=myLoss(Y,Ylabel);
gradients=dlgradient(loss,dlnet.Learnables);
end
The code above is wrong if you have batchNorms, it won't update them. The batchNorms are updated through the State property returnet from forward and assigned to dlnet:
[gradients,state,loss] = dlfeval(@modelGradients,dlnet,dlX,Ylabel);
dlnet.State=state; % THIS!!!
[dlnet,otherOutputs]=rmspropupdate(dlnet,gradients,otherInputs);
function [gradients,state,loss] = modelGradients(dlnet,dlX,Ylabel)
[Y,state]=forward(dlnet,dlX); % THIS!!!
loss=myLoss(Y,Ylabel);
gradients=dlgradient(loss,dlnet.Learnables);
end
Now that dlnet has a State property updated at every forward() call, the batchNorms are updated and your model should converge to a solution that works for predict().
 
I would also like caling MathWorks attention that this detail is only present in documentation in ONE example of GAN networks (in spite of the omnipresence of batchNorm layers in deep learning models) and is never mentioned explicitly.


Not satisfied with the answer ?? ASK NOW

Frequently Asked Questions

MATLAB offers tools for real-time AI applications, including Simulink for modeling and simulation. It can be used for developing algorithms and control systems for autonomous vehicles, robots, and other real-time AI systems.

MATLAB Online™ provides access to MATLAB® from your web browser. With MATLAB Online, your files are stored on MATLAB Drive™ and are available wherever you go. MATLAB Drive Connector synchronizes your files between your computers and MATLAB Online, providing offline access and eliminating the need to manually upload or download files. You can also run your files from the convenience of your smartphone or tablet by connecting to MathWorks® Cloud through the MATLAB Mobile™ app.

Yes, MATLAB provides tools and frameworks for deep learning, including the Deep Learning Toolbox. You can use MATLAB for tasks like building and training neural networks, image classification, and natural language processing.

MATLAB and Python are both popular choices for AI development. MATLAB is known for its ease of use in mathematical computations and its extensive toolbox for AI and machine learning. Python, on the other hand, has a vast ecosystem of libraries like TensorFlow and PyTorch. The choice depends on your preferences and project requirements.

You can find support, discussion forums, and a community of MATLAB users on the MATLAB website, Matlansolutions forums, and other AI-related online communities. Remember that MATLAB's capabilities in AI and machine learning continue to evolve, so staying updated with the latest features and resources is essential for effective AI development using MATLAB.

Without any hesitation the answer to this question is NO. The service we offer is 100% legal, legitimate and won't make you a cheater. Read and discover exactly what an essay writing service is and how when used correctly, is a valuable teaching aid and no more akin to cheating than a tutor's 'model essay' or the many published essay guides available from your local book shop. You should use the work as a reference and should not hand over the exact copy of it.

Matlabsolutions.com provides guaranteed satisfaction with a commitment to complete the work within time. Combined with our meticulous work ethics and extensive domain experience, We are the ideal partner for all your homework/assignment needs. We pledge to provide 24*7 support to dissolve all your academic doubts. We are composed of 300+ esteemed Matlab and other experts who have been empanelled after extensive research and quality check.

Matlabsolutions.com provides undivided attention to each Matlab assignment order with a methodical approach to solution. Our network span is not restricted to US, UK and Australia rather extends to countries like Singapore, Canada and UAE. Our Matlab assignment help services include Image Processing Assignments, Electrical Engineering Assignments, Matlab homework help, Matlab Research Paper help, Matlab Simulink help. Get your work done at the best price in industry.