Lr_find() doesn't work properly

[franva (Winston Fan)]

Update 4

Why is there a turn-around on the Learning Rate/Loss?
What does it indicate?
How to fix it?

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Update 3

I was thinking that my model might be over-fitting. So I decreased my epochs to 12 and keep using the same lr: (1e-8 to 1e-5). Surprisingly, all error_rate for each epoch became 0! Why?? But the cursed train_loss ups-and-downs persist.

epoch	train_loss	valid_loss	error_rate	time
0	0.000218	0.000193	0.000000	01:29
1	0.000667	0.000095	0.000000	01:31
2	0.004174	0.000097	0.000000	01:29
3	0.001321	0.000087	0.000000	01:30
4	0.001333	0.000151	0.000000	01:29
5	0.001109	0.000110	0.000000	01:29
6	0.000294	0.000095	0.000000	01:30
7	0.000113	0.000079	0.000000	01:29
8	0.000556	0.000280	0.000000	01:30
9	0.000861	0.000160	0.000000	01:30
10	0.000789	0.000072	0.000000	01:30
11	0.001177	0.000126	0.000000	01:29

and the plots:

Please help.

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Update 2

Updated to use smaller Learning Rate:

learn.fit_one_cycle(30, max_lr=slice(1e-8,1e-3))

epoch	train_loss	valid_loss	error_rate	time
0	0.006239	0.000118	0.000000	01:30
1	0.000423	0.000087	0.000000	01:29
2	0.001073	0.000031	0.000000	01:29
3	0.000531	0.000078	0.000000	01:29
4	0.000841	0.000396	0.000000	01:29
5	0.001923	0.000126	0.000000	01:29
6	0.000958	0.000046	0.000000	01:29
7	0.001429	0.000668	0.000532	01:29
8	0.002065	0.000368	0.000000	01:28
9	0.001127	0.000116	0.000000	01:29
10	0.001648	0.000192	0.000000	01:29
11	0.001007	0.000020	0.000000	01:30
12	0.001138	0.000095	0.000000	01:29
13	0.002589	0.000206	0.000000	01:29
14	0.000566	0.000140	0.000000	01:30
15	0.000513	0.000075	0.000000	01:29
16	0.001141	0.000137	0.000000	01:30
17	0.000666	0.000105	0.000000	01:29
18	0.000907	0.000095	0.000000	01:29
19	0.000439	0.000128	0.000000	01:30
20	0.002619	0.000094	0.000000	01:28
21	0.000493	0.000021	0.000000	01:29
22	0.000287	0.000085	0.000000	01:30
23	0.000602	0.000167	0.000000	01:30
24	0.000796	0.000142	0.000000	01:29
25	0.003357	0.000249	0.000000	01:29
26	0.000247	0.000181	0.000000	01:31
27	0.000233	0.000143	0.000000	01:30
28	0.000351	0.000143	0.000000	01:30
29	0.000333	0.000173	0.000000	01:29

and here are the plots:

As you can see that the last graph, the train_loss is really bumpy. Why is it?

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Update 1

I updated my lr according to " you want to be 10x back from that point, regardless of slope." and set it to
max_lr=-slice(1e-3, 1e-2)

And here is what I got

epoch	train_loss	valid_loss	error_rate	time
0	0.015970	0.017857	0.006581	09:13
1	0.011153	0.001758	0.000774	09:06
2	0.009547	0.002958	0.001549	09:08
3	0.014085	0.009251	0.003871	09:08
4	0.009021	0.005344	0.001161	09:08
5	0.009346	0.001023	0.000387	09:09
6	0.009408	0.006873	0.001161	09:10
7	0.019754	0.009482	0.001936	09:10
8	0.009297	0.017937	0.003484	09:09
9	0.007004	0.012227	0.002323	09:10
10	0.009249	0.019334	0.003097	09:10
11	0.003321	0.010252	0.001549	09:11
12	0.010526	0.008424	0.000774	09:10
13	0.007408	0.005029	0.001161	09:11
14	0.005817	0.007674	0.001161	09:12
15	0.005499	0.005278	0.000774	09:12
16	0.002524	0.009412	0.001549	09:13
17	0.006877	0.000892	0.000387	09:14
18	0.003429	0.001538	0.000774	09:14
19	0.002009	0.003047	0.000387	09:14
20	0.003262	0.059952	0.001936	09:15
21	0.005491	0.000256	0.000000	09:15
22	0.001810	0.002114	0.000387	09:16
23	0.002307	0.017701	0.002323	09:17
24	0.002877	0.002651	0.000774	09:17
25	0.001547	0.001351	0.000387	09:18
26	0.000105	0.002169	0.000387	09:18
27	0.000331	0.001692	0.000387	09:18
28	0.000755	0.001204	0.000387	09:19
29	0.000563	0.001605	0.000387	09:20

And the plots

What does this mean?

As you can see in the 2nd graph that

1. the loss was very good starting from 1e-08, but I never set my lr to 1e-08, why do I see this??
2. the loss went up and down between 1e-07 and 1e-04 and eventually it soared to almost 0.05 when the lr came back around 4e-05. What does this mean? Overfitting? How come initially when the Learning Rate was around the same value(4e-05) the loss looked okay?
3. from the Batches processed/Loss, I can see that train_loss and valid_loss went together and looked really well. This means the model was trained very well? If it was well trained, why the shot-up at the end of graph 2?
4. I have followed the rule about picking up the correct lr, why does not it work? May I conclude that the lr_find() does not work properly?

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Here is my lr_find() plot

then according to its graph, I picked up the steepest slope section: 1e-2 to 1e-1 as my lr.

Here is the code:
learn.fit_one_cycle(20, max_lr=slice(1e-2,1e-1))

But here is what I got during training

epoch	train_loss	valid_loss	error_rate	time
0	0.017293	0.022473	0.006581	09:11
1	0.063442	0.014093	0.002323	09:08
2	0.126091	0.042731	0.005033	09:07
3	0.234853	0.377233	0.005033	09:04
4	0.447723	0.915372	0.007356	09:04
5	0.379212	3.196698	0.004646	09:03
6	0.347551	0.051682	0.003097	09:02
7	0.503262	nan	0.015099	09:03
8	0.335354	4.139624	0.004259	09:03
9	0.35612	nan	0.024777	09:03
10	0.182476	0.051487	0.00271	09:03
11	0.149758	0.24712	0.00813	09:04
12	0.155585	0.019171	0.000387	09:03
13	0.076157	0.063323	0.00542	09:04
14	0.040974	nan	0.003097	09:03
15	0.019798	0.013353	0.001161	09:03
16	0.013059	0.954418	0.001549	09:04
17	0.007322	0.031414	0.000774	09:05
18	0.002674	0.168147	0.001936	09:05
19	0.004688	0.322064	0.001161	09:04

And here are the plots

learn.recorder.plot_lr()
learn.recorder.plot()
learn.recorder.plot_losses()

​

As you can see the valid_loss is getting worse cyclically.
So my conclusion is lr_find() method doesn’t work properly.

Could someone help to verify it please?

If you want to see the entire code, here it is
only difference is I use to_fp16()
learn = cnn_learner(data, models.resnet50, metrics=error_rate).to_fp16()

Train_loss and valid_loss look very good, but predicting really bad

Update 2 Why is there a turn around at the end?? I have highlighten it by the red circle. [image] Update 1 After some research, I found that someone suggested to turn off Shuffle? But that’s for the Keras + Tensorflow. Do I need to turn off shuffle=False in Fast.Ai? Hi there, new to FastAi, ML and Python. I trained my “Birds Or Not-Birds” model. The train_loss, valid_loss and error_rate were improving. If I only trained 3 epochs, then the model worked(meaning it can recognize whether t…

[LessW2020 (Less)]

Hi - there’s potentially multiple changes that might be needed here.
But to start, I would back off on your learning rate.
You selected very close to the minimum and as a general rule, you want to be 10x back from that point, regardless of slope.

Thus, max_lr=slice(1e-2,1e-1) would likely be a lot better at:

max_lr=slice(1e-3,1e-2)

Secondly, if you have very small batch sizes then I would recommend increasing the batch size. Your training looks super spiky and that can be indicative of a lot of noise batch to batch and the optimizer is having a hard time dealing with it.

Thirdly, try a different optimizer. AdaMod is good for spiky data like this, and I’m finding DiffMod to be the best so far (combination of diffGrad + AdaMod):

lessw2020/Best-Deep-Learning-Optimizers

Finally, you may want to change from fit_one_cycle to flat+ cosine anneal as well.

Hope that helps,
Less

[franva (Winston Fan)]

thanks @LessW2020
I will try the new lr.

2ndly, my batch size is 64, as I applied mix precision fp16 by using to_fp16() to my learner.

3rdly, I am trying to use the DiffMod, but I am not able to import it from diffmod.
I cannot find it on the conda package neither.

Could you please help?

[LessW2020 (Less)]

Hi @franva,

Re: DiffMod - you’ll need to copy the diffmod.py to your working directory and then you should be able to import with no issue.
There’s not a conda or pip package for it at the moment. I’m still testing it.

If you are not able to get it working then let me know but please share your notebook so I can see it and check
Best regards,
Less

[franva (Winston Fan)]

thanks @LessW2020, I was not able to find the diffmod so I adjusted my lr to what you suggested.

Please have a look my update 1 the my post, I added the new training results and plots.

Hopefully, you could pick up something wrong from it.

Also how to share the notebook?

Thanks