ddaini.f
SUBROUTINE DDAINI (X, Y, YPRIME, NEQ, RES, JAC, H, WT, IDID, RPAR,
* IPAR, PHI, DELTA, E, WM, IWM, HMIN, UROUND, NONNEG, NTEMP)
C***BEGIN PROLOGUE DDAINI
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Warning: this routine is not intended to be user-callable.
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C***SUBSIDIARY
C***PURPOSE Initialization routine for DDASSL.
C***LIBRARY SLATEC (DASSL)
C***TYPE DOUBLE PRECISION (SDAINI-S, DDAINI-D)
C***AUTHOR Petzold, Linda R., (LLNL)
C***DESCRIPTION
C-----------------------------------------------------------------
C DDAINI TAKES ONE STEP OF SIZE H OR SMALLER
C WITH THE BACKWARD EULER METHOD, TO
C FIND YPRIME. X AND Y ARE UPDATED TO BE CONSISTENT WITH THE
C NEW STEP. A MODIFIED DAMPED NEWTON ITERATION IS USED TO
C SOLVE THE CORRECTOR ITERATION.
C
C THE INITIAL GUESS FOR YPRIME IS USED IN THE
C PREDICTION, AND IN FORMING THE ITERATION
C MATRIX, BUT IS NOT INVOLVED IN THE
C ERROR TEST. THIS MAY HAVE TROUBLE
C CONVERGING IF THE INITIAL GUESS IS NO
C GOOD, OR IF G(X,Y,YPRIME) DEPENDS
C NONLINEARLY ON YPRIME.
C
C THE PARAMETERS REPRESENT:
C X -- INDEPENDENT VARIABLE
C Y -- SOLUTION VECTOR AT X
C YPRIME -- DERIVATIVE OF SOLUTION VECTOR
C NEQ -- NUMBER OF EQUATIONS
C H -- STEPSIZE. IMDER MAY USE A STEPSIZE
C SMALLER THAN H.
C WT -- VECTOR OF WEIGHTS FOR ERROR
C CRITERION
C IDID -- COMPLETION CODE WITH THE FOLLOWING MEANINGS
C IDID= 1 -- YPRIME WAS FOUND SUCCESSFULLY
C IDID=-12 -- DDAINI FAILED TO FIND YPRIME
C RPAR,IPAR -- REAL AND INTEGER PARAMETER ARRAYS
C THAT ARE NOT ALTERED BY DDAINI
C PHI -- WORK SPACE FOR DDAINI
C DELTA,E -- WORK SPACE FOR DDAINI
C WM,IWM -- REAL AND INTEGER ARRAYS STORING
C MATRIX INFORMATION
C
C-----------------------------------------------------------------
C***ROUTINES CALLED DDAJAC, DDANRM, DDASLV
C***REVISION HISTORY (YYMMDD)
C 830315 DATE WRITTEN
C 901009 Finished conversion to SLATEC 4.0 format (F.N.Fritsch)
C 901019 Merged changes made by C. Ulrich with SLATEC 4.0 format.
C 901026 Added explicit declarations for all variables and minor
C cosmetic changes to prologue. (FNF)
C 901030 Minor corrections to declarations. (FNF)
C***END PROLOGUE DDAINI