2.1.2.1 Data Races in omp_prime.c and pthr_prime.c

As noted in the2.1.1 Complete Listing of omp_prime.c, the order of memory accesses is non-deterministic when code contains a race condition and the computation gives different results from run to run. Each execution of omp_prime.c produces incorrect and inconsistent results because of the data races in the code. An example of the output is shown below:

% cc -xopenmp=noopt omp_prime.c -lm
% a.out | sort -n
0
0
0
0
0
0
0
Number of prime numbers between 2 and 3000: 336
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
...
2971
2999

% a.out | sort -n
0
0
0
0
0
0
0
0
0
Number of prime numbers between 2 and 3000: 325
3
5
7
13
17
19
23
29
31
41
43
47
61
67
71
73
79
83
89
101
...
2971
2999

Similarly, as a result of data-races in pthr_prime.c, different runs of the program may produce incorrect and inconsistent results as shown below.

% cc pthr_prime.c -lm -mt                             
% a.out | sort -n
Number of prime numbers between 2 and 3000: 304
751
757
761
769
773
787
797
809
811
821
823
827
829
839
853
857
859
863
877
881
...
2999
2999

% a.out | sort -n
Number of prime numbers between 2 and 3000: 314
751
757
761
769
773
787
797
809
811
821
823
827
839
853
859
877
881
883
907
911
...
2999
2999