Hello Nat, Yes - i am sure that every Thread is just computing the reduced number - i tested it more than once. They are not producing log output. I have a timer to measure the time basing on the Frequency Performance Counter. After 5 seconds of runtime I do an output of the average computation time. Will now try to eliminate the dll - have a little luck that the required class has no dependencies, so it will take not long - will show the results shorty. Simon