Hi again, I forgot to comment an observation made when writing Glucas for Itanium.
IA64 architecture has a very nice feature: predication. In the DWT used in most GIMPS clients, the normalization and carry phase has a relevant cost in terms of performance. There some branches hard to predict and here the predication substitutes this branches with great success. On small FFT length, the relative cost of carry_and_norm are greater than bigger runlengths, and this is an additional point to know why Itanium is so good at short Mersenne exponents, and why this advantage is decreases when FFT runlength increases. Have a nice Sunday. Guillermo. -- Guillermo Ballester Valor [EMAIL PROTECTED] Granada (Spain) _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
