java - Parallel prime factorization -

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• parallel algorithms generating prime numbers (possibly using hadoop's map reduce) 1 answer

does have idea what's approach parallel prime factorization algorithm ?

i can't figure out @ stage of algorithm should divide threads .. how can think prime factorization in parallel way ?

consider following 1 thread code:

    public static void  primefactorization(arraylist<integer> factors, int num){         //factors array save factorization elements         //num number factorized          int limit = num/2+1;          if(isprime(num))             factors.add(num);          else{             while(num%2==0){                 factors.add(2);                 num=num/2;             }             (int i=3; i<limit; i+=2){                while (isprime(i) && num%i==0){                    factors.add(i);                     num = num/i;                }            }        }     }      private static boolean isprime(int x) {           int top = (int)math.sqrt(x);           (int = 2; <= top; i++)              if ( x % == 0 )                 return false;           return true;     } 

it seems use fork/join framework. seems should able use recursively passing in new factors find. try taking @ recursiveaction well. in pseudo code should able following:

public void getfactors(list<integer> factors, int num){     if(you can find factor){         add 2 factors pool factored further     }     else{         factors.add(num);     }   } 

as side note, might have better performance if started in middle (num/2) , went there opposed starting @ one.