Multiply 2 big integers (System.Numerics) across several cores

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C#

C#4.0

Basically i need a routine that takes BigInt1 and BigInt2 then returns the multiplied BigInt.

I have tried just dividing the biggest BigInt by the smaller one creating a looping routine that runs across several threads adding to a BigInt total although it worked it was (much) slower than just executing BigInt.Multiply on one thread! xD.

my original loop looked something like below inside each thread and despite 100% my CPU it was far too slow.

      private void MultiplicationThread()
       {
           int MyThreadID = GetNextThreadID();
           if (PartsOfBig[MyThreadID] > 0)
           {
               BigInteger NextBlock = new BigInteger();
               NextBlock = BigInteger.Multiply(PartsOfBig[MyThreadID],TheSmall[MyThreadID]);
               lock (TheBigLock)
               {
                   TheBig = BigInteger.Add(TheBig, NextBlock);
               }
           }
       }
}