如何在客户端 GUI 中报告工作人员“事件”

Question

我收到了parallel computing toolbox 的试用版，用于进行一些测试，看看它是如何工作的。

我想要执行的测试之一是看看如何使用此工具箱从 GUI 中运行一些后台处理并报告处理进度。

到目前为止，我已经创建了一个简单的 GUI，其中包含一个用于在后台启动/取消处理的按钮（使用 parfeval）和一个用于报告进度的标签。

一切正常（代码在后台运行，我可以处理后台错误或取消），唯一的问题是在客户端会话中报告后台处理进度：

function [] = TestBackgroundWorker()
%[
    % Create interface
    fig = figure();
    cuo = onCleanup(@()delete(fig));
    stState = uicontrol('Parent', fig, 'Units', 'normalized', 'Position', [0.1 0.7 0.8 0.2], 'Style', 'text', 'String', 'Ready');
    btnOkCancel = uicontrol('Parent', fig, 'Units', 'normalized', 'Position', [0.1 0.1 0.8 0.5], 'Style', 'pushbutton', 'String', 'Go', 'Callback', @(s,e)onOkCancelClicked(fig)); 

    % Backstore
    data = guidata(fig);
    data.bgw = [];
    data.stState = stState;
    data.btnOkCancel = btnOkCancel;
    guidata(fig, data);

    waitfor(fig);   
%]
end
function [] = onBackgroundProgress(fig, ratio, msg)
%[
    % Here I would like to 'BeginInvoke' in client thread
    % to refresh 'ratio/msg' in the GUI.

    % Below code of course doesn't work:
    % 1) It is not synchronized with UI thread
    % 2) It is executed in a session with no display
    data = guidata(fig);
    set(data.stState, 'String', sprintf('%f - %s', ratio, msg));       
%]
end
function [] = onOkCancelClicked(fig)
%[
    % Backstore
    data = guidata(fig);        
    if (~isfield(data, 'bgw'))
        data.bgw = [];        
    end

    if (isempty(data.bgw))

        % Start background work
        set(data.btnOkCancel, 'String', 'Cancel');
        data.bgw = parfeval(@doBackgroundWork, 0, @(r, m)onBackgroundProgress(fig, r, m));
        guidata(fig, data);

        % Wait for error/termination/cancel
        while(true)

            try
                idx = fetchNext(data.bgw, 0.3);
            catch err

                if (~isempty(err.cause) && (strcmp(err.cause{1}.identifier, 'parallel:fevalqueue:ExecutionCancelled')))
                    % Error was due to cancelation
                    uiwait(msgbox('Processing canceled by user!', 'modal'));
                    set(data.btnOkCancel, 'String', 'Go', 'Enable', 'on');
                else
                    % Error real error (TODO: display it in some way)
                    uiwait(msgbox('Processing error!', 'modal'));
                    set(data.btnOkCancel, 'String', 'Go', 'Enable', 'on');
                end

                data.bgw = [];
                guidata(fig, data);
                break;
            end

            if (isempty(idx))
                % Still processing => Enable message pump to read GUI events
                drawnow limitrate; 
            else
                % Processing done
                uiwait(msgbox('Processing done!', 'modal'));
                data.bgw = [];
                guidata(fig, data);
                set(data.btnOkCancel, 'String', 'Go', 'Enable', 'on');
                break;
            end
        end

    else

        % Cancel background work
        set(data.btnOkCancel, 'String', 'Cancelling...', 'Enable', 'off');
        cancel(data.bgw);

    end    
%]
end
function [] = doBackgroundWork(onProgress)
%[
    count = 10;
    for k = 1:count,        
        onProgress((k-1)/count, sprintf('Step %i / %i', k, count)); 
        pause(1);       
    end
%]
end

我很理解这个问题，即回调 onBackgroundProgress 是从没有显示的会话中执行的，所以什么也没有发生（而且它与客户端 GUI 不同步）。

有没有办法从工作人员同步数据并将数据传递到 GUI（在 C# 中我会使用 BeginInvoke）？可能我没有以适当的方式使用工具箱来实现我想要的（似乎更倾向于分布式计算而不是多线程），有没有另一种方法可以用这个工具箱做到这一点？ ...

编辑

我修改了我的代码以将 drawnow 替换为 timer 对象（这可行）并尝试使用 labSend 和 labReceive 将 UI 与后台会话同步（这不起作用）：

%
% PURPOSE:
%
%   Test function to see how to have a responsive GUI while computations
%   are running in the background.
%
% SYNTAX:
%
%   [] = TestBackgroundWorker();
%

%% --- Main routine
function [] = TestBackgroundWorker()
%[
    % Make sure parallel pool is started
    gcp();

    % Create the interface
    % A simple figure with a go/cancel button and a label. 
    fig = figure();
    cuo = onCleanup(@()delete(fig));
    stState = uicontrol('Parent', fig, 'Units', 'normalized', 'Position', [0.1 0.7 0.8 0.2], 'Style', 'text', 'String', 'Ready!');
    btnStartCancel = uicontrol('Parent', fig, 'Units', 'normalized', 'Position', [0.1 0.1 0.8 0.5], 'Style', 'pushbutton', 'String', 'Start', 'Callback', @(s,e)onOkCancelClicked(fig)); 

    % Backstore for later use
    data = guidata(fig);    
    data.stState = stState;
    data.btnStartCancel = btnStartCancel;
    guidata(fig, data);

    % Wait until figure is closed
    waitfor(fig);   
%]
end

%% -- Event handler for 'go/cancel' button in the GUI
function [] = onOkCancelClicked(fig)
%[
    % Backstore
    data = guidata(fig);        
    if (~isfield(data, 'bgw'))
        data.bgw = [];        
    end


    % Depending if background process is running or not
    if (isempty(data.bgw))

        % Start background work
        set(data.btnStartCancel, 'String', 'Cancel');
        data.bgw = parfeval(@doBackgroundWork, 0, @(r, m)onBackgroundProgress(fig, r, m));

        % Start timer to monitor bgw
        data.bgwtimer = timer('ExecutionMode', 'fixedSpacing', 'Period', 0.1, ...
                              'TimerFcn', @(s,e)onBackgroundCheck(fig, data.bgw));

        guidata(fig, data);                          
        start(data.bgwtimer);

    else

        % Cancel background work
        p = gcp('nocreate'); % Make sure parpool is started
        if (~isempty(p))
            cancel(data.bgw);
        end
        set(data.btnStartCancel, 'String', 'Cancelling (please wait)...', 'Enable', 'off');

    end    
%]
end

%% --- Event handlers for monitoring the background worker
function [] = onBackgroundCheck(fig, bgw)
%[    
    try

        idx = fetchNext(bgw, 0.3);
        if (isempty(idx)),

            % Check for messages from the background worker
            if ((numlabs ~= 1) && labProbe)
                data = labReceive();
                onBackgroundProgress(data{:});
            end

        else    
            onBackgroundCompleted(fig);
        end

    catch err

        onBackgroundCompleted(fig, err);

    end    
%]
end
function [] = onBackgroundCompleted(fig, err)
%[
    if (nargin < 2), err = []; end

    if (isempty(err))
        % Normal completion
        uiwait(msgbox('Processing done!', 'Processing', 'help', 'modal'));
    elseif (~isempty(err.cause) && (strcmp(err.cause{1}.identifier, 'parallel:fevalqueue:ExecutionCancelled')))
        % Error was due to cancelation
        uiwait(msgbox('Processing canceled by user!', 'Processing', 'help', 'modal'));
    else
        % Error real error (TODO: display it in some way)
        uiwait(msgbox(sprintf('Processing error: %s', err.message), 'Processing', 'error', 'modal'));                    
    end 

    data = guidata(fig);
    data.bgw = [];
    stop(data.bgwtimer);
    set(data.stState, 'String', 'Ready!');
    set(data.btnStartCancel, 'String', 'Start', 'Enable', 'on');
    guidata(fig, data);        
%]
end

%% --- Event handler for reporting progression status
function [] = onBackgroundProgress(fig, ratio, msg)
%[
    cw = getCurrentWorker();

    if (~isempty(cw))
        % Were are the background thread so send message to the GUI
        % NB: Doing broadcast as I don't know the id of the gui
        labBroadcast(labindex, {fig, ratio, msg });
    else
        % Were are the GUI
        data = guidata(fig);
        set(data.stState, 'String', sprintf('%f - %s', ratio, msg));
    end    
%]
end

%% --- Processing to be performed in the background
function [] = doBackgroundWork(onProgress)
%[
    count = 15;
    for k = 1:count,        
        onProgress((k-1)/count, sprintf('Step %i / %i', k, count)); 
        pause(1);       
    end
%]
end

显然labSend 和labReceive 只能发生在工作人员之间，而不能发生在客户端之间……似乎是一条死胡同。

Answer 1

如果您的唯一目标是监控员工进度，您可能需要查看parfor progress monitor v2。它还让您了解如何建立从工作人员到客户端的套接字连接，您可以使用它来构建更复杂的 UI。