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I've got a small unit test using Intel TBB:
SInt32 nextThreadId = 0; SInt32 maxNumThreads = 0; HashSet activeThreads; Random seedRng; tbb::spin_mutex randMutex; tbb::parallel_for( tbb::blocked_range<SInt32>(0, 1000000), [&](tbb::blocked_range<SInt32>& br) { randMutex.lock(); SInt32 randSeed = seedRng.RandNum(); SInt32 sleepTime = randSeed % 3; SInt32 threadId = nextThreadId; printf("Starting thread %d\n", threadId); activeThreads.InsertInt(threadId); maxNumThreads = (activeThreads.Num() > maxNumThreads) ? activeThreads.Num() : maxNumThreads; nextThreadId++; randMutex.unlock(); sleep(sleepTime); HashTable hashTable; Random random(randSeed); for (SInt32 i = br.begin(); i < br.end(); i++) { SInt32 randNum1 = random.RandNum(); SInt32 randNum2 = random.RandNum(); if (!hashTable.Contains(randNum1)) { hashTable.AtPutInt(randNum1, randNum2); } } for (HashIter i(&hashTable); !i.End(); i.Next()) { SInt32 randNum1 = i.GetKeyInt(); SInt32 randNum2 = i.GetValueInt(); if (randNum1 == randNum2) { printf("Impossible happened\n"); } } randMutex.lock(); activeThreads.RemoveInt(threadId); randMutex.unlock(); }); printf("Finished with %d threads (max %d)\n", nextThreadId, maxNumThreads); exit(0);
The variables randSeed, sleepTime, nextThreadId, maxNumThreads, and activeThreads are all in the critical section and protected by a mutex called randMutex. The programs runs fine on the command line but Intel Inspector reports 42 problems, all data races. Here's the first one
Read: SInt32 threadId = nextThreadId; >>>> Write: nextThreadId++;
Both of these accesses are protected by the spin_mutex. Any idea why it's being reported?
The rest seem to be in other parts of my application that aren't multi-threaded or even executed. My application uses TCmalloc for memory allocation and some of the errors are coming from it.
- Tags:
- CC++
- Debugging
- Development Tools
- Fortran
- Intel® Inspector
- Optimization
- Parallel Computing
- Vectorization
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