multiple cprintf in parallel loop problem

I want to print a secetence with different color in the command windows using 'cprintf':

https://www.mathworks.com/matlabcentral/fileexchange/24093-cprintf-display-formatted-colored-text-in-the-command-window

below are the test code:

    q = parallel.pool.DataQueue;
    afterEach(q, @(args) cprintf(args{:}));
    parfor i=1:1:100
        tic
        pause(0.5)
        time1=toc;
        fprintf(', Reading time:'); send(q,{'Keywords','%4.1f',time1}); fprintf(' seconds,') 
    end

the code runs OK using regular for-loop, but once I changed it into parfor, the printed result are chaos, this may be caused by the combination of fprintf-cprintf-fprintf.

is there anyway to solve this problem?

Thanks!

Yu

Answer 1

[Edric Ellis]

To stop the output being interleaved, you need to send all the stuff to be printed as a single message. Here's one way:

    q = parallel.pool.DataQueue;
    afterEach(q, @multiCprintf);
    parfor i=1:1:100
        tic
        pause(0.5)
        time1=toc;
        % Send multiple sets of things to print in a cell-of-cells
        send(q, {...
            {'Reading time: '}, ...
            {'Keywords', '%4.1f', time1}, ...
            {' seconds\n'}});
    end

    function multiCprintf(argsCell)
    % loop over the outer layer of cells, and call cprintf on
    % the inner layers.
    for idx = 1:numel(argsCell)
        theseArgs = argsCell{idx};
        cprintf(theseArgs{:});
    end
    end

[Yu Li]

Thanks for your answer.

Really fantastic, I've never seen writing parfor like this before.

Thank you~

Yu

[Yu Li]

Hi:

sorry to bother you, I met a further question regarding this topic, just a simple question but I do not know if there is any mistake on my code.

below is the test code:

    warning off all

    q = parallel.pool.DataQueue;
    afterEach(q, @multiCprintf);

    unit='Second';

    send(q,{{'timing: '},{'Keywords','%4.2f',100},{' Seconds\n'}})

    send(q,{{'timing: '},{'Keywords','%4.2f',100},{' %s\n',unit}})

    function multiCprintf(argsCell)
    % loop over the outer layer of cells, and call cprintf on
    % the inner layers.
    for idx = 1:numel(argsCell)
        theseArgs = argsCell{idx};
        cprintf(theseArgs{:});
    end
    end

there are two 'send' in this code, where the unit='Second'. but if you run it, you may see that when I replaced the 'Seconds' with ''%s',unit', the 'Second' is not printed.

I'm not sure if there is any mistake with my code, could you please give me some suggestions?

Thanks!

Yu

[Edric Ellis]

I think this is because cprintf has 2 different syntaxes:

1. cprintf(style, format, ...)

2. cprintf(literalText)

In particular, there's no cprintf(format, ...).

So, when you do

cprintf(' %s\n', 'Second')

cprintf is actually throwing an error because ' %s\n' isn't a valid style. You can fix this by using

{'Text', ' %s\n', unit}

which tells cprintf to print in the plain style.

[Yu Li]

Thank you!