47th Mersenne Prime Confirmed

radiot88 writes to let us know that he heard a confirmation of the discovery of the 47th known Mersenne Prime on NPR's Science Friday (audio here). The new prime, 2^42,643,801 - 1, is actually smaller than the one discovered previously. It was "found by Odd Magnar Strindmo from Melhus, Norway. This prime is the second largest known prime number, a 'mere' 141,125 digits smaller than the Mersenne prime found last August. Odd is an IT professional whose computers have been working with GIMPS since 1996 testing over 1,400 candidates. This calculation took 29 days on a 3.0 GHz Intel Core2 processor. The prime was independently verified June 12th by Tony Reix of Bull SAS in Grenoble, France..."

Comments

Re:Cool processor

[rbarreira]

Do they realize that they can put eight quad-core xeons in a machine and finish the calculation in a single shift instead of waiting a month?

Do you realize that that's less efficient than using those 32 cores to calculate 32 independent numbers?

Re:Why is this useful?

[Rockoon]

Well, for one thing if you need a prime divisor, 2^n-1 primes have some good properties...

Modulus or Division by such numbers can be accomplished with a few fast operations (bitwise Shift/And, a comparison, and maybe a subtraction) instead of a single very slow one (an actual division.)