Re: Lookup table problem

[Ralph Lange <Ralph.Lange@bessy.de>]

 On 21.10.2010 11:21, Steven M. Hartman wrote:
> The ai and ao records included in base support a breakpoint table 
> facility which may be adequate for your needs. But this conversion is 
> to/from RVAL (which is an int) and VAL (which is a double). I hacked a 
> bpt record (based on the ai record) which used the break point table 
> functions included in base to do double to double conversions for my 
> needs. In this way, everything was done in the EPICS database (no 
> sequencer, no subroutine records, etc).

RVALs are integer, of course - now I start remembering .... stupid me.

For a similar application (global tune feed-forward from all ID gaps 
towards multiple families of quadrupoles) Benjamin Franksen at BESSY 
created a new record called cvtRecord to handle large 1/2D feed-forward 
tables in a generic way:


/*
 * General Remarks
 * ===============
 *
 * This record type supports conversion of one or two floating point values
 * into one resulting floating point value. The field METH specifies 
the kind
 * of conversion: LINEAR, via a custom SUBROUTINE, or via one- (1D) or
 * two-dimensional (2D) conversion TABLE. More specifically, if METH is
 *
 * menuCvtMethodLinear:
 *     VAL = XSLO * X + YSLO * Y + VOFF
 *
 * menuCvtMethodSubroutine:
 *     SPEC should be the name of a global subroutine. CSUB is set to the
 *     address of the subroutine.
 *     VAL = CSUB(X, Y, &DPVT)
 *
 * menuCvtMethod1DTable:
 * menuCvtMethod1DTableInverted:
 * menuCvtMethod2DTable:
 *     Conversion uses the csm module. SPEC should be the filename
 *     of the table. CSUB is set to the csm_function handle returned by 
csm.
 *     VAL = csm_y(CSUB, X)         for one-dimensional tables
 *     VAL = csm_x(CSUB, Y)         for one-dimensional inverted tables
 *     VAL = csm_z(CSUB, X, Y)      two-dimensional tables
 */


You should probably ask Benjamin.Franksen@bessy.de for the details and 
the code to this record (and the "csm" module it uses) if you are 
interested.

~Ralph