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Usage
The threadvalue function retrieves the values returned by
the function specified in the threadnew call. The syntax for
its use is
[arg1,arg2,...,argN] = threadvalue(handle)
where handle is the value returned by a threadnew call. Note
that there are issues with nargout. See the examples section
of threadnew for details on how to work around this
limitation. Because the function you have spawned with
threadnew may still be executing, threadvalue must first
threadwait for the function to complete before retrieving
the output values. This wait may take an arbitrarily long
time if the thread function is caught in an infinite loop.
Hence, you can also specify a timeout parameter to
threadvalue as
[arg1,arg2,...,argN] = threadvalue(handle,timeout)
where the timeout is specified in milliseconds. If the wait
times out, an error is raised (that can be caught with a try
and catch block.
In either case, if the thread function itself caused an
error and ceased execution abruptly, then calling
threadvalue will cause that function to raise an error,
allowing you to retrieve the error that was caused and
correct it. See the examples section for more information.
Example
Here we do something very simple. We want to obtain a
listing of all files on the system, but do not want the
results to stop our computation. So we run the system call
in a thread.
--> a = threadnew; % Create the
thread
--> threadstart(a,'system',1,'ls -lrt /'); % Start the
thread
--> b = rand(100)\rand(100,1); % Solve some
equations simultaneously
--> c = threadvalue(a); % Retrieve the
file list
--> size(c) % It is large!
ans =
1 28
--> threadfree(a);
In this example, we force the threaded function to cause an
exception (by calling the error function as the thread
function). When we call threadvalue, we get an error,
instead of the return value of the function
--> a = threadnew
a =
3
--> threadstart(a,'error',0,'Hello world!'); % Will
immediately stop due to error
--> c = threadvalue(a) % The error
comes to us
Error: Thread: Hello world!
--> threadfree(a)
Note that the error has the text Thread: prepended to the
message to help you identify that this was an error in a
different thread.
* FreeMat_Documentation
* FreeMat_Threads
* Generated on Thu Jul 25 2013 17:18:29 for FreeMat by
doxygen_ 1.8.1.1
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