Re: fastest way to add up a billion numbers

*To*: mathgroup at smc.vnet.net*Subject*: [mg73937] Re: [mg73880] fastest way to add up a billion numbers*From*: János <janos.lobb at yale.edu>*Date*: Sat, 3 Mar 2007 01:11:22 -0500 (EST)*References*: <200703021141.GAA04040@smc.vnet.net>

On Mar 2, 2007, at 6:41 AM, Raj wrote: > hi! > > Could somebody tell me what would be the fastest way to add up a > billion numbers(from 1 to 10^9 i.e the first billion numbers) in > Mathematica? > > Ofcourse the answer is n(n+1)/2, but is there any other way in > Mathematica other than the following one: > > Total@@Range[10^9] > > Thanks, > > Raj > Here is a newbie reply: z[n_] = RSolve[{y[1] == 1, y[n] == y[n - 1] + n}, y[n], n] Timing[z[10^9]] {0.0001319999999971344* Second, {{y[1000000000] -> 500000000500000000}}} J=E1nos ---------------------------------------------- Trying to argue with a politician is like lifting up the head of a corpse. (S. Lem: His Master Voice)

**References**:**fastest way to add up a billion numbers***From:*"Raj" <rajanikanth@gmail.com>