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I use TBB todo filtering with IPPfunction "ippsFIR_32fc", each thead works on portion of data. But the results are quite strange. I can see a lot of glitch (very large values)into the output data.
The code is as following:
parallel_for(tbb::blocked_range
void operator() (const blocked_range
{
Int begin = r.begin();
Int end = r.end();
Int nIters = end - begin;
ippsFIR_32fc(m_inP + begin, m_outP + begin, nIters, m_stateP);
}
If I remove the IPP function "ippsFIR_32fc" with "ippsCopy_32f", the multiple thread copy functionality works fine.
Another question is: For float point function, I did not see this type of FIR: complex input data and real filter coefficients. I indeed see complex input data and complex filter coefficients OR real input data and real filter coefficients.
Note: I have already use function 'ippSetNumThreads(1)' to set IPP internal OpenMP threads number to 1.
Could you please help me?
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Also, if you're using IPP with TBB, I'd recommend linking with the unthreaded static libs instead of the DLLs. I don't think there's a way to completely disable OpenMP when linking with the DLLs, and this is why you need to call ippSetNumThreads(1).
Peter
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I don't see anything wrong with the ipp call. It looks correct and you are using a version of the API that can be multi-threaded (any of the ippsFIR API's withSrcDst parameters cannot be multi-threaded). But what is thattilesize in the parallel for? inv.Length/1.5?Try takingthe default tile size and report back with the results.
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...
Could you please help me?
Hi, I could look at the problem and here aretwo questions:
Could you post a small test-case?
What is your TBB version?
Best regards,
Sergey
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Hello,
You may find the "state structures" in IPP here: "state structures that are modified during operation":
http://software.intel.com/sites/products/documentation/hpc/ipp/ippi/ippi_ch2/ch2_function_context_structures.html
so, each threading should has its own status structures. From the code you post here, it looks the "m_stateP" is shared by multiple tasks, which may create incorrect result.
Thanks,
chao
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Hi Chao, It means that an array of filter states has to be used instead, like:
...
IppsFIRState_32f *pState[
...
Since forevery TBBthreadyou can geta ThreadID, or asimilar uniqueID,it is possible to map the pState variables to
a proper processing thread.
Best regards,
Sergey
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thanks for the letting us know. For the FIR function, I think you may just use the complex function as a workaround.
Thanks,
Chao
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