File: RK2INT.FT of Tape: Various/ETH/eth11-1

(Source file text) 

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C  RK2INT.FTN - SAMPLE PROGRAM TO TEST THE FOLLOWING SUBROUTINE:
C  RK2		- TABULATED INTEGRAL OF FIRST-ORDER DIFFERENTIAL
C		  EQUATION BY RUNGE-KUTTA METHOD
	EXTERNAL FCN
C	THE FOLLOWING DIMENSION MUST BE AS LARGE AS THE MAXIMUM
C	NUMBER OF TABULATED VALUES DESIRED
	DIMENSION A(500)
1	FORMAT(3F10.0,2I5)
2	FORMAT(////7X,44HSOLUTION OF DY/DX=FCN(X,Y) BY RK2 SUBROUTINE///,
	110X,2HH=,F7.3,2X,3HX0=,F7.3,2X,3HY0=,F7.3///12X,1HX,18X,4HY(X)//)
3	FORMAT(/10X,F5.2,10X,E15.8)
C
C	OUTPUT CHANNEL = IOUT,INPUT CHANNEL = IN
	IOUT = 2
	IN=1
C
C	READ CONTROL CARD CONTAINING ITEMS X0,Y0,H,JNT,IENT
10	READ(IN,1) X0, Y0, H, JNT, IENT
C	STOP IF IENT = 0
	IF(IENT) 20,40,20
C	WRITE HEADING INFORMATION
20	WRITE(IOUT,2) H,X0,Y0
C	PERFORM INTEGRATION
	CALL RK2(FCN,H,X0,Y0,JNT,IENT,A)
C	WRITE OUTPUT
	STEP=FLOAT(JNT)*H
	X=X0
	DO 30 I=1,IENT
	X=X+STEP+.1E-05
30	WRITE(IOUT,3) X,A(I)
C	GO BACK AND CHECK FOR ADDITIONAL CONTROL CARD
	GO TO 10
40	STOP
	END
	FUNCTION FCN(X,Y)
	FCN = 1./X
	RETURN
	END

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