The code posted by the OP will never execute in parallel, because the parallel keyword does not appear. The fact that the OP got ids different from 0 shows that probably his code was embedded in a parallel directive. However, this is not clear from his post, and might confuse beginners. The minimum sensible example … Read more
private variables are not initialised, i.e. they start with random values like any other local automatic variable (and they are often implemented using automatic variables on the stack of each thread). Take this simple program as an example: #include <stdio.h> #include <omp.h> int main (void) { int i = 10; #pragma omp parallel private(i) { … Read more
The effect on g_qCount is the same, but what’s done is different. An OpenMP critical section is completely general – it can surround any arbitrary block of code. You pay for that generality, however, by incurring significant overhead every time a thread enters and exits the critical section (on top of the inherent cost of … Read more