In each step the SPC's can be redefined using the OP=NEW parameter. To assure
a smooth transition between the values at the end of the previous step and the
newly defined values these must be matched. This matching is performed in
subroutine spcmatch.f. For each SPC i active in a new step the following cases
- a SPC j in the same node and in the same direction was also active in the
previous step; this SPC is identified and the corresponding value, which was
stored in position j of field xbounold before calling spcmatch, is now
stored in position i of field xbounold.
- in the previous step no corresponding SPC (i.e. in the same direction
in the same node) was applied. The appropriate displacement value at the end
of the previous step is stored in position i of field xbounold.