*DECK DX SUBROUTINE DX (U, IDMN, I, J, UXXX, UXXXX) C***BEGIN PROLOGUE DX C***SUBSIDIARY C***PURPOSE Subsidiary to SEPELI C***LIBRARY SLATEC C***TYPE SINGLE PRECISION (DX-S) C***AUTHOR (UNKNOWN) C***DESCRIPTION C C This program computes second order finite difference C approximations to the third and fourth X C partial derivatives of U at the (I,J) mesh point. C C***SEE ALSO SEPELI C***ROUTINES CALLED (NONE) C***COMMON BLOCKS SPLPCM C***REVISION HISTORY (YYMMDD) C 801001 DATE WRITTEN C 891214 Prologue converted to Version 4.0 format. (BAB) C 900402 Added TYPE section. (WRB) C***END PROLOGUE DX C COMMON /SPLPCM/ KSWX ,KSWY ,K ,L , 1 AIT ,BIT ,CIT ,DIT , 2 MIT ,NIT ,IS ,MS , 3 JS ,NS ,DLX ,DLY , 4 TDLX3 ,TDLY3 ,DLX4 ,DLY4 DIMENSION U(IDMN,*) C***FIRST EXECUTABLE STATEMENT DX IF (I.GT.2 .AND. I.LT.(K-1)) GO TO 50 IF (I .EQ. 1) GO TO 10 IF (I .EQ. 2) GO TO 30 IF (I .EQ. K-1) GO TO 60 IF (I .EQ. K) GO TO 80 C C COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=A C 10 IF (KSWX .EQ. 1) GO TO 20 UXXX = (-5.0*U(1,J)+18.0*U(2,J)-24.0*U(3,J)+14.0*U(4,J)- 1 3.0*U(5,J))/(TDLX3) UXXXX = (3.0*U(1,J)-14.0*U(2,J)+26.0*U(3,J)-24.0*U(4,J)+ 1 11.0*U(5,J)-2.0*U(6,J))/DLX4 RETURN C C PERIODIC AT X=A C 20 UXXX = (-U(K-2,J)+2.0*U(K-1,J)-2.0*U(2,J)+U(3,J))/(TDLX3) UXXXX = (U(K-2,J)-4.0*U(K-1,J)+6.0*U(1,J)-4.0*U(2,J)+U(3,J))/DLX4 RETURN C C COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=A+DLX C 30 IF (KSWX .EQ. 1) GO TO 40 UXXX = (-3.0*U(1,J)+10.0*U(2,J)-12.0*U(3,J)+6.0*U(4,J)-U(5,J))/ 1 TDLX3 UXXXX = (2.0*U(1,J)-9.0*U(2,J)+16.0*U(3,J)-14.0*U(4,J)+6.0*U(5,J)- 1 U(6,J))/DLX4 RETURN C C PERIODIC AT X=A+DLX C 40 UXXX = (-U(K-1,J)+2.0*U(1,J)-2.0*U(3,J)+U(4,J))/(TDLX3) UXXXX = (U(K-1,J)-4.0*U(1,J)+6.0*U(2,J)-4.0*U(3,J)+U(4,J))/DLX4 RETURN C C COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS ON THE INTERIOR C 50 CONTINUE UXXX = (-U(I-2,J)+2.0*U(I-1,J)-2.0*U(I+1,J)+U(I+2,J))/TDLX3 UXXXX = (U(I-2,J)-4.0*U(I-1,J)+6.0*U(I,J)-4.0*U(I+1,J)+U(I+2,J))/ 1 DLX4 RETURN C C COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=B-DLX C 60 IF (KSWX .EQ. 1) GO TO 70 UXXX = (U(K-4,J)-6.0*U(K-3,J)+12.0*U(K-2,J)-10.0*U(K-1,J)+ 1 3.0*U(K,J))/TDLX3 UXXXX = (-U(K-5,J)+6.0*U(K-4,J)-14.0*U(K-3,J)+16.0*U(K-2,J)- 1 9.0*U(K-1,J)+2.0*U(K,J))/DLX4 RETURN C C PERIODIC AT X=B-DLX C 70 UXXX = (-U(K-3,J)+2.0*U(K-2,J)-2.0*U(1,J)+U(2,J))/TDLX3 UXXXX = (U(K-3,J)-4.0*U(K-2,J)+6.0*U(K-1,J)-4.0*U(1,J)+U(2,J))/ 1 DLX4 RETURN C C COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=B C 80 UXXX = -(3.0*U(K-4,J)-14.0*U(K-3,J)+24.0*U(K-2,J)-18.0*U(K-1,J)+ 1 5.0*U(K,J))/TDLX3 UXXXX = (-2.0*U(K-5,J)+11.0*U(K-4,J)-24.0*U(K-3,J)+26.0*U(K-2,J)- 1 14.0*U(K-1,J)+3.0*U(K,J))/DLX4 RETURN END