| 1 | SUBROUTINE DTRIDGL(L,AF,BF,CF,DF,XK) |
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| 2 | C DOUBLE PRESCISION VERSION OF TRIDGL |
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| 3 | c PARAMETER (NMAX=201) |
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| 4 | PARAMETER (NMAX=401) |
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| 5 | IMPLICIT REAL (A-H,O-Z) |
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| 6 | DIMENSION AF(L),BF(L),CF(L),DF(L),XK(L) |
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| 7 | DIMENSION AS(NMAX),DS(NMAX) |
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| 8 | C* THIS SUBROUTINE SOLVES A SYSTEM OF TRIDIAGIONAL MATRIX |
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| 9 | C* EQUATIONS. THE FORM OF THE EQUATIONS ARE: |
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| 10 | C* A(I)*X(I-1) + B(I)*X(I) + C(I)*X(I+1) = D(I) |
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| 11 | C* WHERE I=1,L LESS THAN 103. |
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| 12 | C* ..............REVIEWED -CP........ |
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| 13 | AS(L) = AF(L)/BF(L) |
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| 14 | DS(L) = DF(L)/BF(L) |
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| 15 | DO 10 I=2,L |
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| 16 | X=1./(BF(L+1-I) - CF(L+1-I)*AS(L+2-I)) |
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| 17 | AS(L+1-I)=AF(L+1-I)*X |
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| 18 | DS(L+1-I)=(DF(L+1-I)-CF(L+1-I)*DS(L+2-I))*X |
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| 19 | 10 CONTINUE |
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| 20 | XK(1)=DS(1) |
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| 21 | DO 20 I=2,L |
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| 22 | XKB=XK(I-1) |
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| 23 | XK(I)=DS(I)-AS(I)*XKB |
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| 24 | 20 CONTINUE |
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| 25 | 910 FORMAT(/,8X,'AF(I)',7X,'BF(I)',7X,'CF(I)',7X,'DF(I)',7X, |
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| 26 | * 'AS(I)',7X,'DS(I)',7X,'XK(I)',/) |
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| 27 | 915 FORMAT((3X,7(1X,1PE11.4))) |
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| 28 | RETURN |
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| 29 | END |
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