"JVM is not running" Error When m file is called in thread function

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Brian Kim
Brian Kim 2011-3-30
Hi, All. I created a thread function through mexFunction and tried m file in the thread by using mexCallMATLABWithTrap function. However, it did not properly work. I found the error message through the return value of mexCallMATLABWithTrap. It says, "JVM is not running". Why this happens? Does anybody know about this? Is it technically impossible to call m file from the C++ thread function?
As a reference, here is my summarized files.
1. threadtest.cpp
void mexFunction(int nlhs, mxArray *plhs, int nrhs,
mxArray *prhs[])
{
HANDLE hThread;
unsigned threadID;
void* pointer;
hThread = (HANDLE)_beginthreadex( NULL, 0, &MyThreadFunc, pointer, 0, &threadID );
WaitForSingleObject( hThread, INFINITE );
// Destroy the thread object.
CloseHandle( hThread );
}
unsigned __stdcall MyThreadFunc(void * pointer)
{
mexPrintf("I am in thread!!!!\n");
mxArray *returnvalue = mexCallMATLABWithTrap(0, NULL, 0, NULL, "test");
if (returnvalue)
{
mexPrintf("I am here!!!!!\n");
mxArray *plhs = mxGetProperty(returnvalue, 0, "message");
char *buf;
int buflen;
int status;
buflen = (mxGetM(plhs) * mxGetN(plhs)) + 1;
buf = (char*)mxCalloc(buflen, sizeof(char));
if (buf == NULL)
mexErrMsgTxt("Not enough heap space to hold converted string.");
status = mxGetString(plhs, buf, buflen);
if (status == 0)
mexPrintf("The converted string is \n%s.\n", buf);
else
mexErrMsgTxt("Could not convert string data.");
}
_endthreadex( 0 );
return 0;
}
2. test.m
function test()
for i = 1 : 10
fprintf('haha!!!!!!!!!!!!!!!!!!!!\n');
end
Thanks in advance!

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采纳的回答

Richard Alcock
Richard Alcock 2011-3-31
It's fine to create new threads in MEX file, but accessing MATLAB in anyway, including making calls to the MEX API functions, from the spawned thread is not supported.
See http://www.mathworks.com/support/solutions/en/data/1-V3B5T/
  2 个评论
Brian Kim
Brian Kim 2011-3-31
I really appreciate your clear answer. I hope the flexible accessing from threads to MATLAB is supported soon.
Brian Kim
Brian Kim 2011-3-31
I really appreciate your clear answer. I hope the flexible accessing from threads to MATLAB is supported soon.

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更多回答（3 个）

Jan
Jan 2011-3-31
My Matlab 2009a on WinXP-32bit produces a dramatical crash, when I call mexCallMATLAB from different threads.
The article mentioned by Richard is very interesting: You can run a C-thread in parallel, as long as you do not call Matlab API-Functions. But I do not find a documentation about which function should be avoided exactly: mxGetPr? mxCreateDoubleScalar? mxMalloc? mxGetNaN? Multi-threading is fragile and an exact documentation of thread-safe functions would be very helpful.
  2 个评论
Richard Alcock
Richard Alcock 2011-3-31
@Jan - I read "the MEX API is not thread safe" in the link to mean that none of mx* and mex* functions are thread-safe.
Jan
Jan 2011-3-31
@Richard: and if the mx* functions are inlined by "mex -inline"?
All modern processors used for scientific computing have multiple cores. Matlab should be used for scientific computing. Therefore Matlab needs a thread save API. Let's see the new features of 2011a.

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Walfredo
Walfredo 2011-4-15
Hello Brian, I have the same problem. Most of the time, if I try a second time, whatever mexCallMATLAB called would work. I thought it would be ok, but just know, one of my mexCallMATLAB is always failing.
weike yin
weike yin 2011-4-17
????MATLAB engine????????????? ------------------------- You can try to use MATLAB engine, Is't can eval m file in mex spawned thread.

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