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DCL:MATH2:ODELIB: Ordinary Differential Equation (Runge-Kutta): Explanation of Subroutines

3.3.3 ODRKDU

1.

Function

Performs integration using fixed-width steps for the selected algorithm routine. 

2.

Call

CALL ODRKDU(N,ALGOR,FCN,T,TEND,ISTEP,X,WORK)

3.

Explanation of parameters

N	(I)	Number of variables of integration (integrands). (i)
ALGOR	Name of procedure	Name of selected algorithm routine. (i)
FCN	Name of procedure	Name of subroutine that calculates DX. (i)
T	(R)	Value of the independent variable t at which to begin integration. The final step t (TEND) is outputted at RETURN. (i/o)
TEND	(R)	Value of independent variable t at which to end integration. (i)
ISTEP	(I)	Number of steps. (i)
X	R(N)	Outputs the value of the variable of integration at t=TEND for the inputted value of variable at t=T. (i/o)
WORK	R(N,M)	Working variable. M=5 (for ODRK4) and M=3 (for other subroutines).

4.

Notes

(a)

The use of ODRKG (Runge-Kutta-Gill) is recommended whenever possible.

(b)

FCN is provided by the user in the form of a subroutines according to the format:

SUBROUTINE FCN(N,T,X,DX).