This interpolation software relies on the gensub record (written by Andy
Foster).  A copy of a genSub module version that is compatible with this version
of synApps is included with synApps.

The following fields of the gensub record have the following functions in this
software:

VALA[]  independent variable
VALB[]  dependent variable 1
VALC[]  dependent variable 2
A       new value of independent variable, for interp or adding entry
VALN    number of entries
F       interpolation order (1: linear; >1: polynomial)
G       mode (0: Interpolate; 1: Add Entry; 2: Clear All)
B       new value for dependent variable 1 array (used if mode is "Add Entry")
C       new value for dependent variable 2 array (used if mode is "Add Entry")
VALE    successful interpolation (VALE==1)
VALF    interpolation result for dependent variable 1
VALG    interpolation result for dependent variable 2
NOVA    max number of entries in a array - limits table size
NOVB    max number of entries in b array - limits table size
NOVC    max number of entries in c array - limits table size

Note: the code uses only n entries, where n = MIN(nova, novb, novc)

Here's how you use it:

Load VALA, VALB, VALC arrays such that VALB[i] = y1(VALA[i]) and VALC[i] =
y2(VALA[i]), where y1 and y2 are the functions you want to interpolate, and
VALA]] increases with its array index.  You can do this in several ways:
1) with a channel-access client, such as BURT or caput.  This works only
   at run time.
2) by editing the file autosave writes when it's told to save according to
   'interp.req', and then using autosave/restore to load that file.  This
   works only at boot time
3) by setting the interp mode to "Add Entry", specifying interp_y1 and
   interp_y2 values, and then specifying an interp_x value. This works only at
   run time.

However you load the arrays, make sure you do all of the following:

1) set VALE to the number of meaningful points in the VALA, VALB, VALC arrays.
2) load arrays into VALA, VALB, and VALC
3) Make sure VALA[] is monotonically increasing with its array index

The supplied database adds a sort of user interface to the software described
above.  The user writes to $(P)interp_x, and the database sends this value to
the gensub record, which interpolates and, if successful, writes to
$(P)interp_y1 and $(P)interp_y2.  If the user has specified output-link fields
$(P)interp_y1.OUT or $(P)interp_y2.OUT, then the new values will be written to
the PV's named in those links.

Tim Mooney 3/10/2006