INTYD(3)

SYNOPSIS
SUBROUTINE INTYD (T, K, YH, NYH, DKY, IFLAG)

NAME
intyd - Subsidiary to DEBDF

LIBRARY
SLATEC

TYPE
SINGLE PRECISION (INTYD-S, DINTYD-D)

AUTHOR
Watts, H. A., (SNLA)

DESCRIPTION
INTYD approximates the solution and derivatives at T by polynomial interpolation. Must be used in conjunction with the integrator package DEBDF. ---------------------------------------------------------------------- INTYD computes interpolated values of the K-th derivative of the dependent variable vector Y, and stores it in DKY. This routine is called by DEBDF with K = 0,1 and T = TOUT, but may also be called by the user for any K up to the current order. (see detailed instructions in LSODE usage documentation.) ---------------------------------------------------------------------- The computed values in DKY are gotten by interpolation using the Nordsieck history array YH. This array corresponds uniquely to a vector-valued polynomial of degree NQCUR or less, and DKY is set to the K-th derivative of this polynomial at T. The formula for DKY is.. Q DKY(I) = sum C(J,K) * (T - TN)**(J-K) * H**(-J) * YH(I,J+1) J=K where C(J,K) = J*(J-1)*...*(J-K+1), Q = NQCUR, TN = TCUR, H = HCUR. The quantities NQ = NQCUR, L = NQ+1, N = NEQ, TN, and H are communicated by common. The above sum is done in reverse order. IFLAG is returned negative if either K or T is out of bounds. ----------------------------------------------------------------------

SEE ALSO
DEBDF

ROUTINES CALLED
(NONE)

COMMON BLOCKS
DEBDF1

REVISION HISTORY (YYMMDD)
800901 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
891214 Prologue converted to Version 4.0 format. (BAB)
900328 Added TYPE section. (WRB)
910722 Updated AUTHOR section. (ALS)