C RKIN 10
C ..................................................................RKIN 20
C RKIN 30
C SAMPLE PROGRAM FOR RUNGE-KUTTA INTEGRATION OF A GIVEN FUNCTION RKIN 40
C WITH TABULATED OUTPUT - RKINT RKIN 50
C RKIN 60
C PURPOSE RKIN 70
C INTEGRATES THE FUNCTION SUBPROGRAM FUN USING THE INITIAL RKIN 80
C CONDITIONS CONTAINED IN CONTROL CARDS. PRODUCES TABULATED RKIN 90
C OUTPUT. RKIN 100
C RKIN 110
C REMARKS RKIN 120
C NONE RKIN 130
C RKIN 140
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED RKIN 150
C RK2 RKIN 160
C FUN - USER-SUPPLIED FUNCTION SUBPROGRAM GIVING RKIN 170
C DY/DX=FUN(X,Y) RKIN 180
C RKIN 190
C METHOD RKIN 200
C READS CONTROL CARD CONTAINING INITIAL VALUES OF X AND Y, RKIN 210
C STEP SIZE, NUMBER OF STEPS DESIRED BETWEEN TABULATED VALUES,RKIN 220
C AND NUMBER OF TABULATED VALUES REQUIRED. PROGRAM THEN ENTERSRKIN 230
C RK2 TO PERFORM INTEGRATION. MULTIPLE CONTROL CARDS CAN BE RKIN 240
C USED ON THE SAME FUNCTION. RKIN 250
C RKIN 260
C ..................................................................RKIN 270
C RKIN 280
C THE FOLLOWING DIMENSION MUST BE AS LARGE AS THE MAXIMUM RKIN 290
C NUMBER OF TABULATED VALUES DESIRED RKIN 300
C RKIN 310
DIMENSION A(500) RKIN 320
C RKIN 330
EXTERNAL FUN RKIN 340
C RKIN 350
C ...............................................................RKIN 360
C RKIN 370
C IF A DOUBLE PRECISION VERSION OF THIS ROUTINE IS DESIRED, THE RKIN 380
C C IN COLUMN 1 SHOULD BE REMOVED FROM THE DOUBLE PRECISION RKIN 390
C STATEMENT WHICH FOLLOWS. RKIN 400
C RKIN 410
C DOUBLE PRECISION H,XO,YO,A,FUN RKIN 420
C RKIN 430
C THE C MUST ALSO BE REMOVED FROM DOUBLE PRECISION STATEMENTS RKIN 440
C APPEARING IN OTHER ROUTINES USED IN CONJUNCTION WITH THIS RKIN 450
C ROUTINE. RKIN 460
C RKIN 470
C USER FUNCTION SUBPROGRAM, FUN, MUST BE IN DOUBLE PRECISION. RKIN 480
C RKIN 490
C ...............................................................RKIN 500
C RKIN 510
1 FORMAT (3F10.0,2I5) RKIN 520
2 FORMAT(1H1,7X,44HSOLUTION OF DY/DX=FUN(X,Y) BY RK2 SUBROUTINE// RKIN 530
11H ,10X,2HH=,F7.3,2X,3HXO=,F7.3, 2X,3HYO=,F7.3//1H ,12X,1HX,18X, RKIN 540
24HY(X)//) RKIN 550
3 FORMAT(1H ,10X,F5.2,10X,E15.8) RKIN 560
C RKIN 570
C READ CONTROL CARD CONTAINING ITEMS LISTED UNDER METHOD. RKIN 580
C RKIN 590
10 READ(5,1)XO,YO,H,JNT,IENT RKIN 600
C RKIN 610
C CHECK IF CARD IS BLANK. IF SO, RETURN. RKIN 620
C RKIN 630
IF(IENT)20,40,20 RKIN 640
C RKIN 650
C WRITE HEADING INFORMATION. RKIN 660
C RKIN 670
20 WRITE(6,2)H,XO,YO RKIN 680
C RKIN 690
C PERFORM INTEGRATION RKIN 700
C RKIN 710
CALL RK2(FUN,H,XO,YO,JNT,IENT,A) RKIN 720
C RKIN 730
C WRITE OUTPUT RKIN 740
C RKIN 750
STEP=FLOAT(JNT)*H RKIN 760
X=XO RKIN 770
DO 30 I=1,IENT RKIN 780
X=X+STEP RKIN 790
30 WRITE(6,3)X,A(I) RKIN 800
C RKIN 810
C GO BACK AND CHECK FOR ADDITIONAL CONTROL CARD. RKIN 820
C RKIN 830
GO TO 10 RKIN 840
40 RETURN RKIN 850
END RKIN 860