What is the difference between "step out (shift+F11)" and "continue (F)" in MATLAB debugger? When I debug a MATLAB function, both are triggering the cursor to come out of the loop. What is the exact difference between these two?
Continue (dbcont) will cause the program to resume execution and will only stop once it encounters another breakpoint.
Step-Out (dbstep out) will cause the currently executing function to continue and will automatically pause in the calling function regardless of whether you have a breakpoint there or not. Notice that this is referring to stepping out of a function and not a loop.
In your case, I'm assuming you only have a single function (or script) and therefore if you have no manual breakpoints after calling dbcont or dbstep out, they are going to have the same result since they will both just run the rest of the script to completion.
This question already has answers here:
Stop and continue execution from debugger possible?
(6 answers)
Closed 6 years ago.
I am trying to write a program in Matlab which is quite large and I want to stop or pause the execution to see what my variables values are.
I want to stop or pause the execution to see what my variables are.
One alternative is to use keyboard:
keyboard pauses execution of a running program and gives control to
the keyboard. Place the keyboard function in a program at the location
where you want MATLAB® to pause. When the program pauses, the prompt
in the Command Window changes to K>>, indicating that MATLAB is in
debug mode. You then can view or change the values of variables to see
if the new values produce expected results. The keyboard function is
useful for debugging your functions.
To continue executing your function, type dbcont, or type dbquit to quit the debug mode.
If you want to view the variables after a given number of iterations you can insert if ii = stop_point; keyboard; where ii is the iterator of the loop.
Another option is:
Use dbstop. This is shown with an example from the documentation:
Set a breakpoint to stop when n >= 4, and run the code.
dbstop in myprogram at 4 if n>=4
myprogram
Yet another option is to manually insert breakpoints in the MATLAB editor. Click on the left side of the code to insert breakpoints (indicated by a red dot). Now you can view the variable by hovering the mouse over the variable names in the editor
Have a look at this very relevant link to get more information.
Note, the following paragraph is a direct copy of chappjc's answer here. Please upvote his/her answer if you like this approach!
With the release of R2016a, you can just hit the Pause button in the code editor and it will halt right away.
To pause the execution of a program while it is running, in the Editor
tab, click the Pause button. MATLAB pauses execution at the next
executable line*. When your code is running, the Start button will
turn into a pause:
Using the following code:
tmpTable = table([1;2;3]);
for i = 1:5
openvar tmpTable
pause
end
When I run the for loop, all I get is a blank screen in the Variable Editor, except the dimensions of the table are displayed correctly. If I break from the for loop the table displays correctly.
My question is, how do I make this table display programmatically in the for loop, with a pause like command that allows me to inspect the table before moving onto the next one?
What's happening is that pause is pausing the main MATLAB thread which is why you aren't seeing anything in the Variable Editor. You have to make MATLAB enter debug mode if you want the main MATLAB thread to be free.... or of course break the loop as you have discovered.
A "hackish" way to get things going is to insert a keyboard statement instead of pause to force MATLAB to go into debug mode. Once you're there, you'd have to use dbcont to continue onto the next iteration of the loop. This will make MATLAB enter debug mode again as the keyboard statement will be encountered again thus freeing the main thread. This repeats until the last iteration.
Therefore:
tmpTable = table([1;2;3]);
for i = 1:5
openvar tmpTable
keyboard; %// Change
end
You will then see K>> once you execute the first iteration of the loop when you look at the Command Prompt. This signifies that you are in debug mode. To proceed to the next iteration, type in dbcont in the Command Prompt and push ENTER. You can reuse the last command by pushing the Up arrow on your keyboard then push ENTER again and keep doing this until the last iteration of your loop. You will unfortunately have to click back in the Command Prompt as the focus will be placed on the Variable Editor before you enter in the command again. If at any time you want to quit debug mode, use dbquit. This will terminate any code execution and bring you back to the Command Prompt.
This is the only way really to free up the main MATLAB thread at each iteration that I know of.
Is there any way to stop the execution of a matlab program from the debugger like ctrl+c does, but then being able to continue execution (like you can in say c#)?
If not, is there any better way to workaround this other than trying to pre-emptively set break points or dbstop statements in your matlab code?
I would like to be able to interrupt a long running simulation to look at the current state and then continue the simulation.
The two options I'm currently using/considering are
dbstop commands (or (conditional) breakpoints) in the code.
Drawback is that sometimes I don't want to stop the simulation for a few hours, sometimes want to stop after only a few seconds (and I don't necessarily know that in advance) and this doesn't work well with this approach: If I set the break condition to break every 5 minutes, I can't leave matlab running for hours without interaction. If I set the condition to higher, I have to wait too long for the condition to hit.
include code to save the workspace every few seconds/minutes and import the workspace into a second matlab instance. Drawback is that this is a huge hassle and also doesn't necessarily allows me to resume the simulation with the state of the saved workspace then step through the code for a few iterations.
I'm hoping there is a better solution than either of the 2. Thanks for any advice!
Edit: I think what I'm going to do is write simple matlab function that checks an environment variable or a file on disk every iteration and calls dbstop if I set a flag in this file or env. This way I can control when (and if needed which of several) the breakpoint hits from outside matlab by editing the file. Messy, but should work.
This is not necessarily the best way, but you could simulate a file-based signal/interrupt framework. It could be done by checking every once in a while inside the long simulation loop for the existence of a specific file. If it does, you enter interactive mode using the keyboard command.
Something along the lines:
CHECK_EVERY = 10; %# like a polling rate
tic
i = 1; %# loop counter
while true %# long running loop
if rem(i,CHECK_EVERY) == 0 && exist('debug.txt','file')
fprintf('%f seconds since last time.\n', toc)
keyboard
tic
end
%# ... long calculations ...
i = i + 1;
end
You would run your simulation as usual. When you would like to step in the code, simply create a file debug.txt (manually that is), and the execution will halt and you get the prompt:
2.803095 seconds since last time.
K>>
You could then inspect your variables as usual... To continue, simply run return (dont forget to temporarily rename or remove the file). In order to exit, use dbquit
EDIT: Just occurred to me, instead of checking for files, an easier solution would be to use a dummy figure as the flag (as long as the figure is open, keep running).
hFig = figure; drawnow
while true
if ~ishandle(hFig)
keyboard
hFig = figure; drawnow
end
%# ...
pause(0.5)
end
With the release of R2016a, you can just hit the Pause button in the code editor and it will halt right away. The keyboard shortcut is Ctrl+F5.
To pause the execution of a program while it is running, in the Editor tab, click the Pause button. MATLAB pauses execution at the next executable line*.
When your code is running, the Start button will turn into a pause:
Another change with this release is the ability to add/remove breakpoints while running. Previously you couldn't do this, apparently.
You can set a conditional breakpoint in the MATLAB Editor. You can also use DBSTOP to do this. For example, this will set a conditional breakpoint in the file myFcn at line 20 which will stop execution when a loop variable i is a multiple of 500:
dbstop in myFcn.m at 20 if rem(i,500) == 0
Then you can continue execution after you inspect some of your variables.
If saving the workspace to a file is a good proxy for what you want, how about making a simple GUI with a toggle button. In your code, check the state of the button. If the button is depressed, save the state, update a static text to reflect time stamp of last save, unpress the button. Optionally, have a conditional breakpoint based on the state of that toggle button.
Here is an alternate solution using the waitinput File Exchange submission.
The advantage is that you can use it from whithin the current session or in cases where it is troublesome to set up a file. Also it won't leave a file behind on the computer.
The downside is there as well unfortunately, you need to wait for the checking moment before you can terminate and it costs a little bit of time.
for t = 1:10
pause(3) %Doing some calculations
str = waitinput('Enter 1 if you want to stop ',5);
if ~isnan(str)
keyboard; % Enter dbcont if you want to continue from here
end
['moving on, it is now: ' datestr(now)]
pause(3) %Doing some more calculations
end
If you want, you can prevent lines being printed to the screen. In this case you need to enter the input at the time the figure window is open (Look in your start bar on windows).
To summarize, the short code that you can put somewhere like a conditional breakpoint would be:
if ~isnan(waitinput('',5))
keyboard;
end
After certain version (I don't know which one exactly):
Windows: Ctrl + F5
Mac: Command + F5 (I guess)
Unix: I am looking for answer too
After 2016a, there is a button for that on the interface too.
for m = 1:4000
UPDATE_multiDM(driver_info, amplitudes2);
UPDATE_multiDM(driver_info, amplitudes1);
end
Is it possible to execute this line --> set(deviceObj.Acquisition(1), 'State', 'stop'); simultaneously with the for loop above. So during the 1:4000 I will be able to execute this line
The line will stop a oscilloscope from running while the the for loop continues to run until it reaches the end
MATLAB cannot run two processes at the same time (I'm not mentioning Parallel Toolbox now).
If you don't want to run separate session, you can temporary stop the loop, run the command and continue execution.
You can stop by timer (see timer class) or use a simple figure with KeyPressFcn callback. See here, for an example. That example will stop the execution, but you can if statement inside your for-loop to stop it temporarily.