VEC_$IREC3C16                     Domain/OS                      VEC_$IREC3C16


NAME
     vec_$irec3c16 - calculate third-order linear recurrence of 16-bit integer
     vector with constant coefficients

SYNOPSIS (C)
     #include <apollo/base.h>
     #include <apollo/vec.h>

     void vec_$irec3c16(
          short int *start_vec,
          long int &count,
          short int &mult_constant,
          short int &mult_constant_2,
          short int &mult_constant_3,
          short int *result_vec)

SYNOPSIS (Pascal)
     %include '/sys/ins/base.ins.pas';
     %include '/sys/ins/vec.ins.pas';

     procedure vec_$irec3c16(
          in start_vec: univ vec_$integer16_vector;
          in count: integer32;
          in mult_constant: integer16;
          in mult_constant_2: integer16;
          in mult_constant_3: integer16;
          var result_vec: univ vec_$integer16_vector);

SYNOPSIS (FORTRAN)
     %include '/sys/ins/base.ins.ftn'
     %include '/sys/ins/vec.ins.ftn'

           parameter (nvec = 10)

           integer*2 start_vec(nvec), result_vec(nvec)
           integer*2 mult_constant, mult_constant_2, mult_constant_3
           integer*4 count

           call vec_$irec3c16(start_vec, count, mult_constant,
          & mult_constant_2, mult_constant_3, result_vec)

DESCRIPTION
     Vec_$irec3c16 calculates a third-order linear recurrence with constant
     coefficients based on start_vec.  It differs from vec_$rec3c in that the
     vectors being handled contain 16-bit integers.

     This routine reads the first three entries in the array result_vec; it
     then writes count entries into result_vec based on the following formula:

     For each integer I such that 1 <= I <= count,
     result_vec(I+3) = start_vec(I) + (mult_constant x result_vec(I+2))
                       + (mult_constant_2 x result_vec(I+1))
                       + (mult_constant_3 x result_vec(I))

     Notice that result_vec is used both for input and output, and that it
     must be large enough to hold count + 3 entries.

     start_vec
          An input vector.

     mult_constant
          A scalar multiplier.

     mult_constant_2
          A scalar multiplier.

     mult_constant_3
          A scalar multiplier.

     count
          The number of elements to be operated on.

     result_vec
          The vector containing two input values and the result of the
          recurrence calculation.

NOTES
     When vec_$irec3c16 is used to operate on matrixes in C and Pascal,
     start_vec and result_vec are row vectors; in FORTRAN, they are column
     vectors.

     As in all the vec_$ calls,  the result array must not overlap any of the
     input arrays; the result array may be identical to an input, but must not
     contain any smaller subset of an input.   Because of pipelining, using
     overlapping input and output arrays may cause incorrect results.

     Vec_$irec3c16, like all 16-bit integer routines, performs poorly when
     compared to the 32-bit integer routines.  Its use should be avoided wher-
     ever possible, especially on high-performance workstations.

SEE ALSO
     vec_$rec3, vec_$rec3c, vec_$rec3c_i, vec_$drec3c, vec_$drec3c_i,
     vec_$irec3c, vec_$irec3c_i, vec_$irec3c16_i.