Race conditions occur when different threads write to the same location at the same time. This is not necessarily an undefined behavior, but it should be avoided. In the same way, if at least one thread reads from and writes to the same memory unit without synchronization, as a result of atomicity as described above, then a data race occurs. The outcome of the program is unspecified if a data race occurs.
So we implemented a specific case to solve this situation by using multiple thread to create a 2D array in c++ using vector_name.push_back() routine. code
Single: Lets you specify that a section of code should be executed on a single thread, not necessarily the master thread.
has an implicit barrier upon completion of the region, where all threads wait for synchronization.
Critical: specify that code is executed by one thread at a time, it is executed as many times as there are threads.
single and critical are two very different things.