CNS
CNS stands for "Crystallography and NMR System" and is an integrated and full-featured program for the determination and refinement of X-ray crystallographic and NMR structures.
Among its capabilities is simulated annealing molecular dynamics refinement.
There is a parallelization (OpenMP) source code patch for CNS from Kay dot Diederichs at uni-konstanz dot de. It is now distributed with CNS 1.2 as an alternate download. The parallel version features (roughly) a 2-fold speedup on a 4-core machine for a typical simulated annealing omit map run.
Consider also the more automated and user-friendly PHENIX which, although less complete, is under more active development.
Troubleshooting
It was reported that due to an operating system bug in Mac OSX 10.5.x, the program may crash with
forrtl: severe (174): SIGSEGV, segmentation fault occurred Image PC Routine Line Source cns_solve 003548DF Unknown Unknown Unknown cns_solve 00339FBB Unknown Unknown Unknown cns_solve 000F62EC Unknown Unknown Unknown Stack trace terminated abnormally.
This may occur if you are running the program with input redirection, but without output redirection, i.e.,
cns < test.inp
and the input file contains one ore more blank lines.
As a possible remedy, try:
cns < test.inp > test.out