I built a digital scale reader using Darknet's YOLOv4Tiny. It is having trouble confusing 2's and 5's which leads me to believe that I am doing some unwanted data augmentation during training. (The results are mostly correct, and glare could be a factor, but I am expecting better results).
I have referenced this post:
Understanding darknet's yolo.cfg config files
and the darknet github:
https://github.com/AlexeyAB/darknet/wiki/CFG-Parameters-in-the-%5Bnet%5D-section
Below is a link to the yolov4-tiny.cfg that I modified for my model:
https://github.com/AlexeyAB/darknet/blob/master/cfg/yolov4-tiny.cfg
And a snippet from the link above:
[net]
# Testing
#batch=1
#subdivisions=1
# Training
batch=64
subdivisions=1
width=416
height=416
channels=3
momentum=0.9
decay=0.0005
angle=0
saturation = 1.5
exposure = 1.5
hue=.1
Am I correct that angle=0 means that there is no rotation?
Are there any other possible ways I might be augmenting my data that could cause an issue?
Edit: If I wanted, how could I eliminate all data augmentation?
Or do I just need more data (currently 2484 images for 10 digit classes)?
horizontal flip is applied by default, add "flip=0" to disable.
https://github.com/AlexeyAB/darknet
Here, the angle, saturation, exposure, and hue all are part of data augmentation. You can eliminate all data augmentation by setting the value to 0. As data argumentation's values are hyperparameters, modifying the value of these could lead the accuracy to better or worse both. Here I suggest you keep the value given by darknet the same as they found these values are good to get good accuracy. And by all these 4 types of data augmentation darknet initially generated all images. If you add more images without replication it is always good to add more images for the deep learning model to learn the necessary complexity during training.
Related
I have a multi-dimensional, hyper-spectral image (channels, width, height = 15, 2500, 2500). I want to compress its 15 channel dimensions into 5 channels.So, the output would be (channels, width, height = 5, 2500, 2500). One simple way to do is to apply PCA. However, performance is not so good. Thus, I want to use Variational AutoEncoder(VAE).
When I saw the available solution in Tensorflow or keras library, it shows an example of clustering the whole images using Convolutional Variational AutoEncoder(CVAE).
https://www.tensorflow.org/tutorials/generative/cvae
https://keras.io/examples/generative/vae/
However, I have a single image. What is the best practice to implement CVAE? Is it by generating sample images by moving window approach?
One way of doing it would be to have a CVAE that takes as input (and output) values of all the spectral features for each of the spatial coordinates (the stacks circled in red in the picture). So, in the case of your image, you would have 2500*2500 = 6250000 input data samples, which are all vectors of length 15. And then the dimension of the middle layer would be a vector of length 5. And, instead of 2D convolutions that are normally used along the spatial domain of images, in this case it would make sense to use 1D convolution over the spectral domain (since the values of neighbouring wavelengths are also correlated). But I think using only fully-connected layers would also make sense.
As a disclaimer, I haven’t seen CVAEs used in this way before, but like this, you would also get many data samples, which is needed in order for the learning generalise well.
Another option would be indeed what you suggested -- to just generate the samples (patches) using a moving window (maybe with a stride that is the half size of the patch). Even though you wouldn't necessarily get enough data samples for the CVAE to generalise really well on all HSI images, I guess it doesn't matter (if it overfits), since you want to use it on that same image.
I am using DeepLabv3+ and I am running some tests. For my first run I used an output_stride=16 and atrous_rates=[6, 12, 18] and in the 2nd run I used output_stride=8 and atrous_rates=[12,24, 36]. Then I used tensorboard to see the results and I could notice that the heatmaps look larger and one "unit" is 4x bigger than the run with output_stride=16.
output_stride=16
output_stride=8
I would like to know what is the reason behing this behaviour and the consequences on my mIOU metric.
regards
According to the paper Encoder-Decoder with Atrous Separable Convolution for Semantic Image Segmentation (3.1 DeeplabV3+ as an encoder), output_stride simply means the ratio between image input size and feature map output size (before global pooling). So change output_stride will change the output result.
just copy form link.
I am rather new to deep learning, please bear with me. I have a GAN, with model structure copy-pasted from: https://machinelearningmastery.com/how-to-develop-a-generative-adversarial-network-for-an-mnist-handwritten-digits-from-scratch-in-keras/
It will train for say 100-200 epochs with pretty ok results, then suddenly generator loss drops to zero... here is excerpt from log:
epoch,step,gen_loss,discr_loss
...
189,25,0.208,0.712
189,26,3.925,1.501
189,27,0.269,1.400
189,28,7.814,2.536
189,29,0.000,3.387 // here?!?
189,30,0.000,7.903
189,31,16.118,7.745
189,32,16.118,8.059
189,33,16.118,8.059
189,34,16.118,8.059
... etc, it never recovers
Is this a problem of vanishing gradients? Anything else I’m missing?
In the blogpost comments people argues about the GAN's collapse problem, here you have a comment:
There were problems with the discriminator collapsing to zero on occasions. This seems to be a known feature of GANs. Do any established GAN hacks help with this?
Looking at the discriminator after 100 epochs, it was in a confused state where everything passed into it was circa 50% probability real/fake. I colour coded some generated examples based on disriminator probability (red = fake, green = real, blue = unsure based on an arbitrary banding) and as you mentioned the subjective versus discriminator output does not always tie up. (example posted on linkedin). There was not enough spread in discriminator probability output to make this meaningful.
GANs are very hard to train and it is very usual that the generator or the discriminator becomes so strong that the other can't improve itself, so if you for instance try to generate pictures I would recommend to use progressive GANS what improves the stability a lot and allow to go for high resolution images.
My task here is to find a way to get a suggested value of the most important feature or features. By changing into the suggested values of the features, I want the classification result to change as well.
Snapshot of dataset
The following is the procedures that I have tried so far:
Import dataset (shape: 1162 by 22)
Build a simple neural network (2 hidden layers)
Since the dependent variable is simply either 0 or 1 (classification problem), I onehot-encoded the variable. So it's either [0, 1] or [1,0]
After splitting into train & test data, I train my NN model and got accuracy of 77.8%
To know which feature (out of 21) is the most important one in the determination of either 0 or 1, I trained the data using Random Forest classifier (scikit-learn) and also got 77.8% accuracy and then used the 'feature_importances_' offered by the random forest classifier.
As a result, I found out that a feature named 'a_L4' ranks the highest in terms of relative feature importance.
The feature 'a_L4' is allowed to have a value from 0 to 360 since it means an angle. In the original dataset, 'a_L4' comprises of only 12 values that are [5, 50, 95, 120, 140, 160, 185, 230, 235, 275, 320, 345].
I augmented the original dataset by directly adding all the possible 12 values for each cases giving a new dataset of shape (1162x12 by 22).
I imported the augmented dataset and tested it on the previously trained NN model. The result was a FAILURE. There hardly was any change in the classification meaning almost no '1's switched to '0's.
My conclusion was that changing the values of 'a_L4' was not enough to bring a change in the classification. So I additionally did the same procedure again for the 2nd most important feature which in this case was 'b_L7_p1'.
So writing all the possible values that the two most important features can have, now the new dataset becomes the shape of (1162x12x6 by 22). 'b_L7_p1' is allowed to have 6 different values only, thus the multiplication by 6.
Again the result was a FAILURE.
So, my question is what might have I done wrong in the procedure described above? Do I need to keep searching for more important features and augment the data with all the possible values they can have? But since this is a tedious task with multiple procedures to be done manually and leads to a dataset with a huge size, I wish there was a way to construct an inference-based NN model that can directly give out the suggested values of a certain feature or features.
I am relatively new to this field of research, so could anyone please tell me some key words that I should search for? I cannot find any work or papers regarding this issue on Google.
Thanks in advance.
In this case I would approach the problem in the following way:
Normalize the whole dataset. As you can see from the dataset your features have different scales. It is utterly important that you make all features to have the same scale. Have a look at: https://scikit-learn.org/stable/modules/generated/sklearn.preprocessing.StandardScaler.html
The second this that I would do now is train and evaluate a model (It can be whatever you want) to get a so called baseline model.
Then, I would try PCA to see whether all features are needed. Maybe you are including unnecessary sparsity to the model. See: https://scikit-learn.org/stable/modules/generated/sklearn.decomposition.PCA.html
For example if you set the n_components in PCA to be 0.99 then you are reducing the number of features while retaining as 0.99 explained variance.
Then I would train the model to see whether there is any improvement. Please note that only by adding the normalization itself there should be an improvement.
If I want to see by the dataset itself which features are important I would do: https://scikit-learn.org/stable/modules/generated/sklearn.feature_selection.SelectKBest.html This would select a specified number of features based on some statistical test lets say: https://scikit-learn.org/stable/modules/generated/sklearn.feature_selection.chi2.html
Train a model and evaluate it again to see whether there is some improvement.
Also, you should be aware that the NNs can perform feature engineering by themselves, so computing feature importance is redundant in a way.
Let me know whether you will see any improvements.
I am training an object detector for my own data using Tensorflow Object Detection API. I am following the (great) tutorial by Dat Tran https://towardsdatascience.com/how-to-train-your-own-object-detector-with-tensorflows-object-detector-api-bec72ecfe1d9. I am using the provided ssd_mobilenet_v1_coco-model pre-trained model checkpoint as the starting point for the training. I have only one object class.
I exported the trained model, ran it on the evaluation data and looked at the resulted bounding boxes. The trained model worked nicely; I would say that if there was 20 objects, typically there were 13 objects with spot on predicted bounding boxes ("true positives"); 7 where the objects were not detected ("false negatives"); 2 cases where problems occur were two or more objects are close to each other: the bounding boxes get drawn between the objects in some of these cases ("false positives"<-of course, calling these "false positives" etc. is inaccurate, but this is just for me to understand the concept of precision here). There are almost no other "false positives". This seems much better result than what I was hoping to get, and while this kind of visual inspection does not give the actual mAP (which is calculated based on overlap of the predicted and tagged bounding boxes?), I would roughly estimate the mAP as something like 13/(13+2) >80%.
However, when I run the evaluation (eval.py) (on two different evaluation sets), I get the following mAP graph (0.7 smoothed):
mAP during training
This would indicate a huge variation in mAP, and level of about 0.3 at the end of the training, which is way worse than what I would assume based on how well the boundary boxes are drawn when I use the exported output_inference_graph.pb on the evaluation set.
Here is the total loss graph for the training:
total loss during training
My training data consist of 200 images with about 20 labeled objects each (I labeled them using the labelImg app); the images are extracted from a video and the objects are small and kind of blurry. The original image size is 1200x900, so I reduced it to 600x450 for the training data. Evaluation data (which I used both as the evaluation data set for eval.pyand to visually check what the predictions look like) is similar, consists of 50 images with 20 object each, but is still in the original size (the training data is extracted from the first 30 min of the video and evaluation data from the last 30 min).
Question 1: Why is the mAP so low in evaluation when the model appears to work so well? Is it normal for the mAP graph fluctuate so much? I did not touch the default values for how many images the tensorboard uses to draw the graph (I read this question: Tensorflow object detection api validation data size and have some vague idea that there is some default value that can be changed?)
Question 2: Can this be related to different size of the training data and the evaluation data (1200x700 vs 600x450)? If so, should I resize the evaluation data, too? (I did not want to do this as my application uses the original image size, and I want to evaluate how well the model does on that data).
Question 3: Is it a problem to form the training and evaluation data from images where there are multiple tagged objects per image (i.e. surely the evaluation routine compares all the predicted bounding boxes in one image to all the tagged bounding boxes in one image, and not all the predicted boxes in one image to one tagged box which would preduce many "false false positives"?)
(Question 4: it seems to me the model training could have been stopped after around 10000 timesteps were the mAP kind of leveled out, is it now overtrained? it's kind of hard to tell when it fluctuates so much.)
I am a newbie with object detection so I very much appreciate any insight anyone can offer! :)
Question 1: This is the tough one... First, I think you don't understand correctly what mAP is, since your rough calculation is false. Here is, briefly, how it is computed:
For each class of object, using the overlap between the real objects and the detected ones, the detections are tagged as "True positive" or "False positive"; all the real objects with no "True positive" associated to them are labelled "False Negative".
Then, iterate through all your detections (on all images of the dataset) in decreasing order of confidence. Compute the accuracy (TP/(TP+FP)) and recall (TP/(TP+FN)), only counting the detections that you've already seen ( with confidence bigger than the current one) for TP and FP. This gives you a point (acc, recc), that you can put on a precision-recall graph.
Once you've added all possible points to your graph, you compute the area under the curve: this is the Average Precision for this category
if you have multiple categories, the mAP is the standard mean of all APs.
Applying that to your case: in the best case your true positive are the detections with the best confidence. In that case your acc/rec curve will look like a rectangle: you'd have 100% accuracy up to (13/20) recall, and then points with 13/20 recall and <100% accuracy; this gives you mAP=AP(category 1)=13/20=0.65. And this is the best case, you can expect less in practice due to false positives which higher confidence.
Other reasons why yours could be lower:
maybe among the bounding boxes that appear to be good, some are still rejected in the calculations because the overlap between the detection and the real object is not quite big enough. The criterion is that Intersection over Union (IoU) of the two bounding boxes (real one and detection) should be over 0.5. While it seems like a gentle threshold, it's not really; you should probably try and write a script to display the detected bounding boxes with a different color depending on whether they're accepted or not (if not, you'll get both a FP and a FN).
maybe you're only visualizing the first 10 images of the evaluation. If so, change that, for 2 reasons: 1. maybe you're just very lucky on these images, and they're not representative of what follows, just by luck. 2. Actually, more than luck, if these images are the first from the evaluation set, they come right after the end of the training set in your video, so they are probably quite similar to some images in the training set, so they are easier to predict, so they're not representative of your evaluation set.
Question 2: if you have not changed that part in the config file mobilenet_v1_coco-model, all your images (both for training and testing) are rescaled to 300x300 pixels at the start of the network, so your preprocessings don't matter.
Question 3: no it's not a problem at all, all these algorithms were designed to detect multiple objects in images.
Question 4: Given the fluctuations, I'd actually keep training it until you can see improvement or clear overtraining. 10k steps is actually quite small, maybe it's enough because your task is relatively easy, maybe it's not enough and you need to wait ten times that to have significant improvement...