drkfs.f
SUBROUTINE DRKFS (DF, NEQ, T, Y, TOUT, INFO, RTOL, ATOL, IDID, H,
+ TOLFAC, YP, F1, F2, F3, F4, F5, YS, TOLD, DTSIGN, U26, RER,
+ INIT, KSTEPS, KOP, IQUIT, STIFF, NONSTF, NTSTEP, NSTIFS, RPAR,
+ IPAR)
C***BEGIN PROLOGUE DRKFS
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Warning: this routine is not intended to be user-callable.
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C***SUBSIDIARY
C***PURPOSE Subsidiary to DDERKF
C***LIBRARY SLATEC
C***TYPE DOUBLE PRECISION (DERKFS-S, DRKFS-D)
C***AUTHOR Watts, H. A., (SNLA)
C***DESCRIPTION
C
C Fehlberg Fourth-Fifth Order Runge-Kutta Method
C **********************************************************************
C
C DRKFS integrates a system of first order ordinary differential
C equations as described in the comments for DDERKF .
C
C The arrays YP,F1,F2,F3,F4,F5,and YS (of length at least NEQ)
C appear in the call list for variable dimensioning purposes.
C
C The variables H,TOLFAC,TOLD,DTSIGN,U26,RER,INIT,KSTEPS,KOP,IQUIT,
C STIFF,NONSTF,NTSTEP, and NSTIFS are used internally by the code
C and appear in the call list to eliminate local retention of
C variables between calls. Accordingly, these variables and the
C array YP should not be altered.
C Items of possible interest are
C H - An appropriate step size to be used for the next step
C TOLFAC - Factor of change in the tolerances
C YP - Derivative of solution vector at T
C KSTEPS - Counter on the number of steps attempted
C
C **********************************************************************
C
C***SEE ALSO DDERKF
C***ROUTINES CALLED D1MACH, DFEHL, DHSTRT, DHVNRM, XERMSG
C***REVISION HISTORY (YYMMDD)
C 820301 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890831 Modified array declarations. (WRB)
C 891024 Changed references from DVNORM to DHVNRM. (WRB)
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900328 Added TYPE section. (WRB)
C 900510 Convert XERRWV calls to XERMSG calls, change GOTOs to
C IF-THEN-ELSEs. (RWC)
C 910722 Updated AUTHOR section. (ALS)
C***END PROLOGUE DRKFS