NuShellX shares the same modular design as NuShell. The transition operator program NuTra can take any combination of the operators I , N, a+, a-, a+a-, a+a+ and a-a- for the neutrons and protons giving a total of about 22 useful possibilties. On of these 22 (a+a- x a+a-) is used by the Lanczos routines. The combinations (a+ x a+a+ and a+a+ x a+a+) give 3 particle and alpha transfer spectroscopic factors. These are unique to NuShellX (and NuShell). The programs NuTrx and NuClx convert the output of NuTra to decay rates and spectroscopic amplitudes
On a 3GHz Xeon Duo with 4GB of memory the release version will diagonalise the 0+ of 56Ni in full fp-shell, dimension 15,443,684, in 19 hours. But note that the code only requires 1.3GB of memory plus system overhead for this case. But for full fp-shell calculations for 48Cr, the maximum time to diagonalize any matrix is about 19 mins for J=6, dimension 226,259, while the 0+, dimension 41,355, will take 38 seconds which is about 9 times faster than NuShell. For 48Cr the memory requirements are minimal. When N/=Z much faster times will be possible. All the above times are for the thick restart Lanczos method and 10 converged eigenvalues.
NushellX will be probably 5.5 and 10 times faster than published times for Antoine (Strasbourg group m-scheme cousin of Nathan) for 0+ states in 56Ni and 52Fe correcting for processor differences. But in absolute terms it will be 16.8 and 30 times faster on the Xeon Duo for 0+ states in 56Ni and 52Fe. A calculation that took 14 hours and 60GB memory with Nushell has been done in less than 3 mins with 2GB memory with a pre-release version of NuShellX on the same machine. This is nearly 300 times faster. Note however that for small calculations NuShell will be faster than NuShellX and isospin can be used with NuShell but not with NuShellX. But it is quick and easy to calculate the isospin of final states.
For larger calculations 4 or more processors are recommended to speed up the calculations, but the memory requirement also increases with the number of processors since each processor must have its own copy of the new Lanczos vector and its own buffers for intermediate storage. A large processor cache is also advantageous as is a 10,000 RPM disk.
Note that the diagonalisation of the Hamiltonian matrix has undergone extensive testing for some aspects particularly stability. The transition rate codes have not had extensive testing. There are restrictions on truncation options in this code. These are necessary to get the maximum efficiency from the code and maintain the high speed. Truncations are allowed for neutrons and protons separately, but truncations that have to be applied taking neutrons and protons into account simultaneously are now accommodated albeit inefficiently.
Many thanks to Alex Brown (brown@nscl.msu.edu) who has now tested the codes. Many thanks to Mihai Horoi (horoi@phy.cmich.edu) for finding an error in earlier versions and has tested the codes. The first publication using the new codes in print. There have been other reports from workshops and conferences presenting results from code.
Many very useful and helpful email exchanges with Jussi Toivanen are gratefully acknowledged.