task: OpenMP directive name required

Question

Here is my code:

#include <stdio.h>
#include <cstdlib>
#include <locale>
#include <omp.h>

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;

ll fib(int n) {
    if (n <= 1)
        return 1;
    ll a, b;
#pragma omp task shared(a)
    a = fib(n - 1);
#pragma omp task shared(b)
    b = fib(n - 2);
#pragma omp taskwait
    return a + b;
}

int main(int argc, char* argv[]) {
    setlocale(LC_ALL, "");
    int n;
    scanf_s("%d", &n);
    printf("Result: %lld\n", fib(n));
    system("pause");
    return 0;
}

Visual Studio returns C3001 error "task: OpenMP directive name required".
If I comment all the "pragma" it works fine, so there must be a problem with OpenMP. Some other program with "#pragma omp parallel" works fine, it's just the problem with the "task" directive.
What could be the problem?

you need to define an environment of parallel tasks e.g. started with "#pragma omp parallel" followed by "#pragma omp single nowait". — Bort
– Bort, Commented May 30, 2018 at 12:53
@Bort like this? #pragma omp parallel { #pragma omp single { %code% } } — Dmitry Shabat
– Dmitry Shabat, Commented May 30, 2018 at 13:03
E.g. yes. See your error code here. Although, I don't know about supported openmp versions in visual studio. So acraig5075 might be right and it won't work anyways. — Bort
– Bort, Commented May 30, 2018 at 14:18

acraig5075 · Accepted Answer · 2018-05-30 13:00:48Z

6

Visual C++ supports the OpenMP 2.0 standard.

OpenMP introduced tasks with OpenMP 3.0

i.e. It's unsupported.

answered May 30, 2018 at 13:00

acraig5075

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