DFEHL(3)

SYNOPSIS
SUBROUTINE DFEHL (DF, NEQ, T, Y, H, YP, F1, F2, F3, F4, F5, YS, + RPAR, IPAR)

NAME
dfehl - Subsidiary to DDERKF

LIBRARY
SLATEC

TYPE
DOUBLE PRECISION (DEFEHL-S, DFEHL-D)

AUTHOR
Watts, H. A., (SNLA)

DESCRIPTION
Fehlberg Fourth-Fifth Order Runge-Kutta Method ********************************************************************** DFEHL integrates a system of NEQ first order ordinary differential equations of the form DU/DX = DF(X,U) over one step when the vector Y(*) of initial values for U(*) and the vector YP(*) of initial derivatives, satisfying YP = DF(T,Y), are given at the starting point X=T. DFEHL advances the solution over the fixed step H and returns the fifth order (sixth order accurate locally) solution approximation at T+H in the array YS(*). F1,---,F5 are arrays of dimension NEQ which are needed for internal storage. The formulas have been grouped to control loss of significance. DFEHL should be called with an H not smaller than 13 units of roundoff in T so that the various independent arguments can be distinguished. This subroutine has been written with all variables and statement numbers entirely compatible with DRKFS. For greater efficiency, the call to DFEHL can be replaced by the module beginning with line 222 and extending to the last line just before the return statement. **********************************************************************

SEE ALSO
DDERKF

ROUTINES CALLED
(NONE)

REVISION HISTORY (YYMMDD)
820301 DATE WRITTEN
890831 Modified array declarations. (WRB)
891214 Prologue converted to Version 4.0 format. (BAB)
900328 Added TYPE section. (WRB)
910722 Updated AUTHOR section. (ALS)