Primecount is a command-line program and C++ library that counts the
primes below an integer x<=10**31 using highly optimized implementations
of the combinatorial prime counting algorithms.
Primecount includes implementations of all important combinatorial prime
counting algorithms known up to this date all of which have been
parallelized using OpenMP. Primecount contains the first ever open
source implementations of the Deleglise-Rivat algorithm and Xavier
Gourdon's algorithm (that works). Primecount also features a novel load
balancer that is shared amongst all implementations and that scales up
to hundreds of CPU cores. Primecount has already been used to compute
several world records e.g. pi(10**27)
(http://www.mersenneforum.org/showthread.php?t=20473) and
nth_prime(10**24) (https://oeis.org/A006988).
