DDAJAC(3)

SYNOPSIS
SUBROUTINE DDAJAC (NEQ, X, Y, YPRIME, DELTA, CJ, H, IER, WT, E, * WM, IWM, RES, IRES, UROUND, JAC, RPAR, IPAR, NTEMP)

NAME
ddajac - Compute the iteration matrix for DDASSL and form the LU-decomposition.

LIBRARY
SLATEC (DASSL)

TYPE
DOUBLE PRECISION (SDAJAC-S, DDAJAC-D)

AUTHOR
Petzold, Linda R., (LLNL)

DESCRIPTION
C----------------------------------------------------------------------- THIS ROUTINE COMPUTES THE ITERATION MATRIX PD=DG/DY+CJ*DG/DYPRIME (WHERE G(X,Y,YPRIME)=0). HERE PD IS COMPUTED BY THE USER-SUPPLIED ROUTINE JAC IF IWM(MTYPE) IS 1 OR 4, AND IT IS COMPUTED BY NUMERICAL FINITE DIFFERENCING IF IWM(MTYPE)IS 2 OR 5 THE PARAMETERS HAVE THE FOLLOWING MEANINGS. Y = ARRAY CONTAINING PREDICTED VALUES YPRIME = ARRAY CONTAINING PREDICTED DERIVATIVES DELTA = RESIDUAL EVALUATED AT (X,Y,YPRIME) (USED ONLY IF IWM(MTYPE)=2 OR 5) CJ = SCALAR PARAMETER DEFINING ITERATION MATRIX H = CURRENT STEPSIZE IN INTEGRATION IER = VARIABLE WHICH IS .NE. 0 IF ITERATION MATRIX IS SINGULAR, AND 0 OTHERWISE. WT = VECTOR OF WEIGHTS FOR COMPUTING NORMS E = WORK SPACE (TEMPORARY) OF LENGTH NEQ WM = REAL WORK SPACE FOR MATRICES. ON OUTPUT IT CONTAINS THE LU DECOMPOSITION OF THE ITERATION MATRIX. IWM = INTEGER WORK SPACE CONTAINING MATRIX INFORMATION RES = NAME OF THE EXTERNAL USER-SUPPLIED ROUTINE TO EVALUATE THE RESIDUAL FUNCTION G(X,Y,YPRIME) IRES = FLAG WHICH IS EQUAL TO ZERO IF NO ILLEGAL VALUES IN RES, AND LESS THAN ZERO OTHERWISE. (IF IRES IS LESS THAN ZERO, THE MATRIX WAS NOT COMPLETED) IN THIS CASE (IF IRES .LT. 0), THEN IER = 0. UROUND = THE UNIT ROUNDOFF ERROR OF THE MACHINE BEING USED. JAC = NAME OF THE EXTERNAL USER-SUPPLIED ROUTINE TO EVALUATE THE ITERATION MATRIX (THIS ROUTINE IS ONLY USED IF IWM(MTYPE) IS 1 OR 4) C-----------------------------------------------------------------------

ROUTINES CALLED
DGBFA, DGEFA

REVISION HISTORY (YYMMDD)
830315 DATE WRITTEN
901009 Finished conversion to SLATEC 4.0 format (F.N.Fritsch)
901010 Modified three MAX calls to be all on one line. (FNF)
901019 Merged changes made by C. Ulrich with SLATEC 4.0 format.
901026 Added explicit declarations for all variables and minor cosmetic changes to prologue. (FNF)
901101 Corrected PURPOSE. (FNF)