Changes in primecount 6.3:

This is a minor new release, the API and ABI (Application binary interface) are backwards compatible.

The memory usage of the PiTable and SegmentedPiTable has been reduced by about 2x, this speeds up the computation of the easy special leaves (S2_easy & AC formulas) by up to 30% for large pi(x) computations with x ≥ 1e23. Furthermore, the partial sieve function a.k.a. phi(x, a) has been improved significantly, it now runs 3 to 5x faster for most input. phi(x, a) is used extensively by many other functions such as pi_legendre(x) and pi_meissel(x) which now also run up to 5x faster.

• PiTable.cpp: Reduce memory usage by 2x.
• SegmentedPiTable.cpp: Reduce memory usage by 2x.
• Sieve.cpp: Reduce memory usage of counters array by 2x.
• phi.cpp: Fixed integer overflow #39.
• phi.cpp: Cache 40x more phi(x, a) results.
• phi.cpp: Use pi(x) if a > pi(sqrt(x)).
• phi.cpp: Use larger c constant if phi(x, larger_c) is cached.
• generate_phi.hpp: Same optimizations as phi.cpp.
• LoadBalancer.cpp: Tune for new phi(x, a) implementation.
• FactorTable.hpp: Reduce number of branches.
• DFactorTable.hpp: Reduce number of branches.