*DECK DEFEHL SUBROUTINE DEFEHL (F, NEQ, T, Y, H, YP, F1, F2, F3, F4, F5, YS, + RPAR, IPAR) C***BEGIN PROLOGUE DEFEHL C***SUBSIDIARY C***PURPOSE Subsidiary to DERKF C***LIBRARY SLATEC C***TYPE SINGLE PRECISION (DEFEHL-S, DFEHL-D) C***AUTHOR Watts, H. A., (SNLA) C***DESCRIPTION C C Fehlberg Fourth-Fifth order Runge-Kutta Method C ********************************************************************** C C DEFEHL integrates a system of NEQ first order C ordinary differential equations of the form C dU/DX = F(X,U) C over one step when the vector Y(*) of initial values for U(*) and C the vector YP(*) of initial derivatives, satisfying YP = F(T,Y), C are given at the starting point X=T. C C DEFEHL advances the solution over the fixed step H and returns C the fifth order (sixth order accurate locally) solution C approximation at T+H in the array YS(*). C F1,---,F5 are arrays of dimension NEQ which are needed C for internal storage. C The formulas have been grouped to control loss of significance. C DEFEHL should be called with an H not smaller than 13 units of C roundoff in T so that the various independent arguments can be C distinguished. C C This subroutine has been written with all variables and statement C numbers entirely compatible with DERKFS. For greater efficiency, C the call to DEFEHL can be replaced by the module beginning with C line 222 and extending to the last line just before the return C statement. C C ********************************************************************** C C***SEE ALSO DERKF C***ROUTINES CALLED (NONE) C***REVISION HISTORY (YYMMDD) C 800501 DATE WRITTEN C 890831 Modified array declarations. (WRB) C 891009 Removed unreferenced statement label. (WRB) C 891214 Prologue converted to Version 4.0 format. (BAB) C 900328 Added TYPE section. (WRB) C 910722 Updated AUTHOR section. (ALS) C***END PROLOGUE DEFEHL