Comments: which code to choose for your calculation

From ALPSWiki

• looper: models with inversion symmetry in spin space
• dirloop_sse: models with anisotropy that breaks inversion symmetry in spin space e.g., Heisenberg models in a magnetic field

Simple Heisenberg models without a magnetic field can be simulated with either of these. Looper has the smaller range of applicability, but if applicable, it shows the best performance (shortest autocorrelation time).