On Friday, 29 of July 2005 23:14, Michal Schmidt wrote: > Rafael J. Wysocki wrote: > > On Friday, 29 of July 2005 21:46, Michal Schmidt wrote: > > > >>The function calc_nr uses an iterative algorithm to calculate the number > >>of pages needed for the image and the pagedir. Exactly the same result > >>can be obtained with a one-line expression. > > > > > > Could you please post the proof? > > > > Rafael > > OK, attached is a proof-by-brute-force program. It compares the results > of the original function and the simplified one. > > This is its output: > > $ ./calc_nr2 > checked 0 ... > checked 100000000 ... > checked 200000000 ... > checked 300000000 ... > checked 400000000 ... > checked 500000000 ... > checked 600000000 ... > checked 700000000 ... > checked 800000000 ... > checked 900000000 ... > checked 1000000000 ... > checked 1100000000 ... > checked 1200000000 ... > checked 1300000000 ... > checked 1400000000 ... > checked 1500000000 ... > checked 1600000000 ... > checked 1700000000 ... > checked 1800000000 ... > checked 1900000000 ... > checked 2000000000 ... > checked 2100000000 ... > First difference at 2130706433: -2147483646 x -2147483647 > > It means that the two functions give the same results for sensible > values of the input argument. > They results only differ when they overflow into negative values. At > this point both of the results are useless. Thanks, fine. :-) Greets, Rafael -- - Would you tell me, please, which way I ought to go from here? - That depends a good deal on where you want to get to. -- Lewis Carroll "Alice's Adventures in Wonderland"
