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59 lines
1.7 KiB
Fortran
59 lines
1.7 KiB
Fortran
*DECK CHKSN4
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SUBROUTINE CHKSN4 (MBDCND, NBDCND, ALPHA, BETA, COFX, SINGLR)
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C***BEGIN PROLOGUE CHKSN4
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C***SUBSIDIARY
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C***PURPOSE Subsidiary to SEPX4
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C***LIBRARY SLATEC
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C***TYPE SINGLE PRECISION (CHKSN4-S)
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C***AUTHOR (UNKNOWN)
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C***DESCRIPTION
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C
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C This subroutine checks if the PDE SEPX4
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C must solve is a singular operator.
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C
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C***SEE ALSO SEPX4
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C***ROUTINES CALLED (NONE)
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C***COMMON BLOCKS SPL4
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C***REVISION HISTORY (YYMMDD)
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C 801001 DATE WRITTEN
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C 890531 Changed all specific intrinsics to generic. (WRB)
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C 900402 Added TYPE section. (WRB)
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C***END PROLOGUE CHKSN4
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C
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COMMON /SPL4/ KSWX ,KSWY ,K ,L ,
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1 AIT ,BIT ,CIT ,DIT ,
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2 MIT ,NIT ,IS ,MS ,
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3 JS ,NS ,DLX ,DLY ,
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4 TDLX3 ,TDLY3 ,DLX4 ,DLY4
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LOGICAL SINGLR
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EXTERNAL COFX
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C***FIRST EXECUTABLE STATEMENT CHKSN4
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SINGLR = .FALSE.
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C
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C CHECK IF THE BOUNDARY CONDITIONS ARE
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C ENTIRELY PERIODIC AND/OR MIXED
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C
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IF ((MBDCND.NE.0 .AND. MBDCND.NE.3) .OR.
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1 (NBDCND.NE.0 .AND. NBDCND.NE.3)) RETURN
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C
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C CHECK THAT MIXED CONDITIONS ARE PURE NEUMAN
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C
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IF (MBDCND .NE. 3) GO TO 10
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IF (ALPHA.NE.0.0 .OR. BETA.NE.0.0) RETURN
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10 CONTINUE
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C
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C CHECK THAT NON-DERIVATIVE COEFFICIENT FUNCTIONS
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C ARE ZERO
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C
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DO 30 I=IS,MS
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XI = AIT+(I-1)*DLX
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CALL COFX (XI,AI,BI,CI)
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IF (CI .NE. 0.0) RETURN
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30 CONTINUE
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C
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C THE OPERATOR MUST BE SINGULAR IF THIS POINT IS REACHED
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C
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SINGLR = .TRUE.
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RETURN
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END
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