However, it has been mostly rewritten (60-70% of the code), especially in platform-specific parts (memory allocation, disk input/output, network), mathematic functions (e.g., matrix operations), and quantum chemistry methods (such as Hartree–Fock method, Møller–Plesset perturbation theory, and density functional theory).
Since October 2008, the project is no longer associated with GAMESS (US) and the Firefly rename occurred.
[2] On July 25, 2012, a state of the art edition of Firefly, version 8.0.0 RC, was launched for public beta testing.
A relative comparison has shown that it is far faster and more reliable than the prior edition, Firefly 7.1.G.
Firefly's unique capabilities include XMCQDPT2, a reformulation of Nakano's multi-state multi-configuration quasi-degenerate perturbation theory (MCQDPT) correcting for some of its deficiencies.