>40 seconds waiting for Undefined function or variable error 2017b

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Adam Danz
Adam Danz on 30 Oct 2017
Answered: Ryan Santos on 30 Aug 2019
I'm using matlab 2017b on a windows 7 64 bit machine and when I accidentally reference a variable or function that doesn't exist, Matlab consumes a significant amount of time in 'busy' mode before throwing the error: 'Undefined function or variable'. I've paused the execution a few times to see where the bottleneck is and it has always opened the findUnlicensedFunctions() function. To cause this error, I type in any nonsense command such as "ttt" in the command window where ttt does not refer to any function or variable. Using tic/toc just before and after the call to ttt resulted in 43 seconds waiting for the error. Is anyone else experiencing this or might it be specific to my environment? I upgraded last week from 2016a and did not have this problem before.
Adam Danz
Adam Danz on 12 Apr 2019
Unforunately this is still a very frustrating problem (r2019a).
If you're connected to a wireless network and you call a function or a variable that contains a typo and therefore no longer corresponds to an existing function or variable, the delay for the error message to appear is up to a minute sometimes - just waiting for Matlab in the 'busy' state. Ctrl+c does not stop this process. Pausing it does not speed it up but eventually terminates in findUnlicensedFunctions().

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Accepted Answer

Adam Danz
Adam Danz on 22 Apr 2018
Edited: Adam Danz on 25 Aug 2019
Apparently when a variable or function is called but not available, matlab searches network locations on the matlab path and if those connections are no longer accessible, this delay occurs. To confirm that this is what's causing the unbearably long deley, I turned off/on my internet connection(s) and the problem vanished when there wasn't a connection but immediately returned when there was a connection. The link below contains suggestions on how to troubleshoot this issue but doesn't fix it for good.
After dealing with the same problem off and on for years, I wrote a function that fixes it. The function below creates a GUI that lists all network drives that appear in your Matlab history. You can select any (or all) of the drives that you no longer have access to and it will remove those from your history. The effect was immediate for me and I no longer had to deal with the wait time. Other options in the GUI allow you to restore the history from a backup if needed. It's a pretty simple.
If you're interested (and if you're a PC user) please give it a shot and let me know if it works for you, too.

More Answers (6)

Jakub Krizan
Jakub Krizan on 3 Apr 2018
I have never experienced this issue in Matlab 2017b, but it started to happen since I have upgraded to Matlab 2018a. The behavior is the same as Adam Danz describes. I am using Windows 10 64bit (build 1709)
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Adam Danz
Adam Danz on 13 Apr 2018
I've also upgraded to 2018a and am disappointed that this is still an issue. Often times the delay is unbearable. (Windows 7, 64bit)

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Mary Abbott
Mary Abbott on 2 Nov 2017
Thank you for reporting this. We have been able to reproduce this on our end, and I have forwarded the details to our development team so that they can investigate it further.

Jose on 9 Sep 2018
Edited: Jose on 9 Sep 2018
Hello I am getting the same problem and I am getting crazy. In my case are not 40 seconds. Sometimes it takes 10 minutes. And turnning off the net connections dont solve anything. It happens anyway. I am desperate

Jose on 27 Sep 2018
Edited: Jose on 27 Sep 2018
Today I installed the 2018b version and the problem is still there. So, I installed it, I ran it and I typed in the command line a variable that I didn t declare before, >> r and enter and it took 1 minute almost 2 to answer: Undefined function or variable 'r'.
Someone in Matlab is taking actions? I am really fed up of it.
ElCapitan OS
Zachary Eilon
Zachary Eilon on 28 Aug 2019
This solution did not fix it for me - I think the history is saved somewhere else, so as soon as one navigates to a new directory, it repopulates even having cleared it with the above code. However, selecting "Clear History" under the "Current Folder" tab of the MATLAB preferences did the trick for permanently clearing the history.

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Jose on 15 Oct 2018
In my case is solved. I was using external hard drives (usb connected). It turns out that by accident the power supply was off and I noticed that I was not having latencies anymore. I connected them and the latencies were there again. I am happy because I am not dealing with that delays anymore but in the other hand I can not use my hard drives during my working day with Matlab which is not nice.

Ryan Santos
Ryan Santos on 30 Aug 2019
Hey all,
First off, sorry for the problems everyone has been facing with the error recovery system. We added the feature in 2017b where upon encountering an unknown function or identifier, MATLAB will search through a users "current working directory" history and make suggestions based on that. Unfortunately what could sometimes happen is that some items in that history could no longer be accessable, causing the delay you're seeing here.
The workaround, as you already know, is to remove those problematic directories from your history. Though we understand that it is still frustrating and not always realistic since some directories could become innaccessable as your working and still cause an initial delay. We've been seeing more and more of this feedback from customers, so we are going to take some steps to try to alleviate this problem in a future release. We're working on it!
Ryan Santos

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