c - omp_set_num_threads should I use it every time or can set it once? -

i have program calls sequently 100 functions - want use omp_set_num_threads every function. should use before every time call ith function? or can use once, lets after int main(int argc, char **argv) , used every function call?

it looks this:

omp_set_num_threads(val); if(call_me_i)    call_ith_function;   omp_set_num_threads(val); if(call_me_i+1)    call_ith+1_function; ... 

short answer: need set number of threads once, unless want change later. once set, "remembered".

it sounds me have individual functions have parallel code in them, , want make sure indeed run in parallel. when have large number of if statements, want consider switch.

omp_set_num_threads(val); //<<< set once switch(whatfunction) {   case fun1:     callfunction1();     break;   case fun2:     callfunction2();     break;   default:     // etc }  void callfunction1() {   int ii;   #pragma omp parallel   // <<<< loop run in parallel >>>>>   for(ii=0; ii<100; ii++) {     // stuff   }   printf("done\n"); printf("really done\n"); printf("totally done\n"); // << not in parallel }  void callfunction2() {   int jj;   for(jj=0; jj<100; jj++) {     // stuff   }  // <<<< loop not run in parallel since there no #pragma in front of }