Compiler Error C3039

'var' : index variable in OpenMP 'for' statement cannot be a reduction variable

Remarks

An index variable is implicitly private, so the variable cannot be used in a reduction clause in the enclosing parallel directive.

Example

The following example generates C3039:

// C3039.cpp
// compile with: /openmp /c
int g_i;

int main() {
   int i;

   #pragma omp parallel reduction(+: i)
   {
      #pragma omp for
      for (i = 0; i < 10; ++i)   // C3039
         g_i += i;
   }
}