Setting labels and titles of axes extremely slow

In my use case the setting of labels and the title of axes takes up to a second or more each and I would like to know why and how I can avoid this.

My use case is as follows: I have programmatically created a 1300x800 figure using:

mainfig = figure(...
  'Units','Pixels',...
  'Position',[50 70 1300 80],...
  'Name','abc',...
  'DockControls','off',...
  'Resize','off',...
  'NumberTitle','off');

and added about 6~8 custom sized axes to it using:

axes(...
  'Parent',mainfig,
  'Units','pixels',
  'Position',ex [1 2 3 4]);

Creating this window, these axes and the plots that use these axes using:

plot(ax,...)

is fine and takes up next to no time in the profiler.

However when I add labels and a title to the axes I am seeing up to 1.5 seconds of runtime for each item set. Here is an example from the MATLAB R2015a profiler (problem occurs in R2015a, R2016b, R2017b):

Line Code                              Calls Total Time %Time
48   ax.XLabel.String = 'blablabla...  1     1.412 s    33.3%
50   ax.Title.String = 'blablabla...   1     1.379 s    32.5%
49   ax.YLabel.String = 'blablabla...  1     1.375 s    32.4%
...

The profiler shows these as 100% self time and does not show the innards of these lines.

Also, in this case using xlabel() or ax.XLabel.String makes no difference in time cost.

So, to repeat, I would like to know why and how I can avoid this. It should not be normal that putting a single piece of text somewhere in a GUI costs an eternity of CPU time.

A test case is provided here: https://pastebin.com/wBjxydju

[Jan]

Can you provide a minimal working example code? I did not observe such a delay on my R2016b/64/Win7. Which effect has a drawnow before setting the labels?

[JM]

A test case is shown here: https://pastebin.com/wBjxydju. In this version creation of each label takes 150 ms on R2016b/64/Linux (CentOS) which adds up quickly for a more complex GUI. Commenting drawnow does not change results.

My results are as follows:

• Creating window 1 out of 10...
• Created window in 0.39 seconds
• Creating window 2 out of 10...
• Created window in 0.57 seconds
• Creating window 3 out of 10...
• Created window in 0.49 seconds
• Creating window 4 out of 10...
• Created window in 0.34 seconds
• Creating window 5 out of 10...
• Created window in 0.32 seconds
• Creating window 6 out of 10...
• Created window in 0.38 seconds
• Creating window 7 out of 10...
• Created window in 0.46 seconds
• Creating window 8 out of 10...
• Created window in 0.39 seconds
• Creating window 9 out of 10...
• Created window in 0.47 seconds
• Creating window 10 out of 10...
• Created window in 0.38 seconds

[Ben Drebing]

Can you give us the output of running this command in MATLAB:

 opengl info

This might have to do with your graphics card.

[Massimo Ciacci]

For me the delay depends on the data size. I guess profiler assigns the time to the lines following plot instead on to the plot itself...

                          Version: '4.6.0 NVIDIA 391.35'
                           Vendor: 'NVIDIA Corporation'
                         Renderer: 'GeForce GTX 1070/PCIe/SSE2'
                   MaxTextureSize: 32768
                           Visual: 'Visual 0x09, (RGBA 32 bits (8 8 8 8), Z depth 24 bits, Hardware acceleration, Doub...'
                         Software: 'false'
        SupportsGraphicsSmoothing: 1
    SupportsDepthPeelTransparency: 1
       SupportsAlignVertexCenters: 1
                       Extensions: {375x1 cell}
               MaxFrameBufferSize: 32768

[Massimo Ciacci]

I confirm that quering properties of axis is slower when there is a lot of stuff plotted on them. A good workaround which I found myself again to use today is to fix all axis properties BEFORE plotting anything on them.

Answer 1

[Massimo Ciacci]

I think I found a nice workaround

% (1) set all curves invsibile, for a good speed up for label handles retrieval
axChild   = get(gca,'Children');
allCurves = findobj(axChild,'type','line');
set(allCurves,'visible','off'); 

% (2) fix/change labels

% (3) restore visible
set(allCurves,'visible','on'); 
 

as an example you can try the following plot code which plots 20M points on two curves

close all
clearvars

tic
profile off
profile on

SPEED_UP = 1;

NN = 20e6;
figure(100); grid on; hold on; axh=gca;
plot(1:NN,1:NN);
plot(1:NN,-(1:NN));

if SPEED_UP
    axChild   = get(gca,'Children');
    allCurves = findobj(axChild,'type','line');
    set(allCurves,'visible','off');
end

xlabel('x'); ylabel('y');
set(axh,'xscale','log');
xlh = get(axh,'xlabel');

if SPEED_UP
    %Restore visibility
    set(allCurves,'visible','on');
end

profile viewer
toc

Elapsed time is 2.147400 seconds. SPEED_UP = 0

Elapsed time is 0.690461 seconds. SPEED_UP = 1

[Massimo Ciacci]

I also noticed that this trick can help speed up linkaxes in the same way, by setting allCurves to invisible in both axes before linking ...

[Justin]

Strangely neither workaround (setting labels before plotting nor hiding graph objects when setting labels) seems to work when you are plotting histograms rather than lines. At least in 2020b anyway.