If there is a center of inversion, the code automatically tries to shift the atomic coordinates such that the crystal has inversion symmetry. If you want to inhibit that, put a line saying:
no restore_inversion
Finally, you can specify whether you want the symmetry-operations to be generated by the code, or if they should be read from the file SYMMETRYOPS. If number_symmetry_ops is followed by -1, then the symmetry operations are determined by the code itself. If number_symmetry_ops is , the matrices for the symmetry operation are read in from the file. The file format is the same as the printout in e.g. OUT. For an example file, see SYMMETRYOPShttp://civet.berkeley.edu/pfrommer/SYMMETRYOPS
Default: number_symmetry_ops -1
If number_symmetry_ops is followed by -2, then the symmetry operations are determined by the code itself, but nonzero fractional translations are ignored. This could be useful for supercells.