matlab - MATLAB同步代码

Question

MATLAB中Java的“同步”等价于什么？

假设我有两个计时器，它们都可以修改一个变量（即矩阵）M。如果它们同时触发，它们会同时尝试更改 M（这可能会导致错误）吗？MATLAB 会自动同步这些操作吗？

Answer 1

Matlab 99% 是单线程的（另外 1% 与这个问题并不真正相关）。所以没有synchronized可用的关键字。

但是，某些操作是可中断的，这意味着 GUI 回调或计时器可以在意外时间暂停操作。这可能会导致在多头系统中可以观察到的一些相同问题。

为防止中断，interruptible请在可用时使用该属性（通常在 GUI 对象上）。这应该处理在处理 GUI 回调时防止重入行为的需要。例如

set(gcf,'Interruptible','off')

但是，这不处理与计时器相关的中断。

---

看起来两个定时器不能互相中断，所以不需要同步。但是，计时器可以中断主要活动。

经过一些测试后，这可能发生在文档中隐含的pause、drawnow、figure或call 附近。getframe它也可能发生在其他调用附近，包括一些 tic/toc 调用和对 Java 的调用。

我不知道与Interruptible计时器或函数的属性平行，即使可能需要它。根对象0有一个Interruptible属性，但它没有效果（根据文档，并已确认）。

注意：这与我提供的先前答案（参见历史）相比有很大变化，代表最近的学习。我之前的示例使用了两个计时器，它们似乎相互消除了冲突。本例使用一个定时器加主函数操作。

---

下面包含一个示例，演示了一种不可中断的情况，以及两种功能some_work被中断的情况。

function minimum_synchronization_example

%Defune functions to test for interruptability
%(these are all defined at the bottom of the file)
fnList = {
    @fn_expectedNoInterruption
    @fn_expectedInterruption
    @fn_unexpectedInterruption
    };
for ix = 1:length(fnList)
    disp(['---Examples using ' func2str(fnList{ix}) '--------'])
    test_subfunction_for_interrupt_allowed(fnList{ix});
end
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function test_subfunction_for_interrupt_allowed(fn)
%Setup and start a timer to execute "some_work"
t1 = timer();
set(t1,...
    'Name','PerformSomeWorkTimer1', ...
    'TimerFcn', @(~,~) some_work('Timer-1', fn), ...
    'ExecutionMode','fixedSpacing', ...
    'Period', 0.4, ...
    'TasksToExecute', 6, ...
    'BusyMode', 'drop')
start(t1);

%Then immediately execute "some_work" from the main function
for ix = 1:6
    some_work('MainFun', fn);
    pause(0.2);
end

%The timer and the loop take about the same amount of time, stop and delete
%the timer before moving on
stop(t1);
delete(t1);
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function some_work(displayString, subFunctionWhichMayAllowInterrupts)
%Initialize persistent, if needed.
%This records then umber of active calls to this function.
persistent entryCount
if isempty(entryCount)
    entryCount = 0;
end

%Record entry
entryCount = entryCount+1;
tic;

%Perform some work  (Inverting a 3000-by-3000 matrix takes about 1 sec on my computer)
[~] = inv(randn(3000));

%Run subfunction to see if it will be interrupted
subFunctionWhichMayAllowInterrupts();

%Display results. How many instances of this function are currently active?
if entryCount>1;
    strWarning = 'XXX ';
else
    strWarning = '    ';
end
disp([strWarning ' <' sprintf('%d',entryCount) '> [' displayString '] ; Duration: ' sprintf('%7.3f',toc)]);

%Record exit
entryCount = entryCount-1;
end


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function fn_expectedNoInterruption
x = 1+1;
end

function fn_expectedInterruption
drawnow;
end

function fn_unexpectedInterruption
m = java.util.HashMap();
end