Difference between static and dynamic schedule in OpenMP in C

Question

I've got two similar codes.

First

#pragma omp parallel for shared(g) private(i) schedule(dynamic, 1)
for(i = (*g).actualNumberOfChromosomes; i < (*g).maxNumberOfChromosomes; i++)
{
    AddCrossoverChromosome(g, i); // it doesnt change actualNumberOfChromosomes
    #pragma omp atomic
    (*g).actualNumberOfChromosomes++;
}

Second

#pragma omp parallel for shared(g) private(i) schedule(static, 1)
for(i = (*g).actualNumberOfChromosomes; i < (*g).maxNumberOfChromosomes; i++)
{
    AddCrossoverChromosome(g, i); // it doesnt change actualNumberOfChromosomes
    #pragma omp atomic
    (*g).actualNumberOfChromosomes++;
}

The only difference is in the first line. First code works fine, but the second one crashes. Why?

Problem is somewhere in actualNumberOfChromosomes, but I would like to understand why, and not just solve this. I could solve this by creating addition variable p and assigning actualNumberOfChromosomes to it and changing the loop so that i was equal to p.

Answer 1

The difference between static schedule type and dynamic schedule type is that with static the chunks can be pre-computed as well as decided how to scheduled to threads during compilation itself, whereas with dynamic the same thing is done during run-time.

With the usage of dynamic, it involves some complex mechanisms like deadlock handling mechanism, load handling, etc.

You can get some more info at: http://openmp.blogspot.com.