With many variables streaming past, there is a need to keep track on some
particular variables. It would be rather inefficient and laborious to need
to continually call uvprobvr, to check on particular variables. The
uvtrack routine is used to instruct the uv routines to keep track
of when certain variable changes its value, and to perform special
processing on these variables at a later stage. Typically uvtrack
would be called soon after uvopen, marking all the variables of
particular interest. The special processing that the uv routines perform
is dictated by the switches argument. This is a string,
consisting of several characters, each character representing a particular
processing step to be taken. Currently there are two switches -
u and c. The u switch is used by uvupdate, whereas
the c switch is used by uvcopyvr.
uvupdate returns a .true. value if one of the variables, marked
with the u switch, has been updated ``recently''
(see Section 2.5.10).
The routine uvcopyvr copies variables marked with the c
switch, from the input dataset (given by tin) to the output
dataset (given by tout) if they have changed ``recently'' (see
Section 2.5.10). You need only
mark the variables in the input dataset.