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PROGRAM TEST
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IMPLICIT NONE
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C
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INTEGER LDB, LDIWRK, LDWORK, N, NRHS
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PARAMETER (N = 4)
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PARAMETER (LDB = N)
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PARAMETER (LDIWRK = N)
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PARAMETER (LDWORK = N)
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PARAMETER (NRHS = 1)
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C
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DOUBLE PRECISION B(LDB,NRHS), DIAG(N), DLOWER(N-1)
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DOUBLE PRECISION DUPPER(N-1)
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INTEGER ICOL, INFO, IROW
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C
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EXTERNAL DGTSV
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INTRINSIC ABS, MAX
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C
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C Initialize the arrays DLOWER, DIAG, and DUPPER to store the
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C first subdiagonal, the diagonal, and the first superdiagonal
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C of the coefficient matrix A shown below. Initialize the
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C array B to store the right hand side matrix b shown below.
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C
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C 2 -1 0
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C A = 1 2 -1 b = 2
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C 1 2 -1 4
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C 1 2 11
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C
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DATA DLOWER / 1.0D0, 1.0D0, 1.0D0 /
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DATA DIAG / 2.0D0, 2.0D0, 2.0D0, 2.0D0 /
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DATA DUPPER / -1.0D0, -1.0D0, -1.0D0 /
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DATA B / 0.0D0, 2.0D0, 4.0D0, 1.1D1 /
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C
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PRINT 1000
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DO 100, IROW = 1, N
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PRINT 1010, (0.0D0, ICOL = 1, IROW - 2),
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$ (DLOWER(ICOL + 1), ICOL = ABS(IROW - 2), IROW - 2),
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$ DIAG(IROW),
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$ (DUPPER(IROW), ICOL = 1, MIN(1, N - IROW)),
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$ (0.0D0, ICOL = IROW + 2, N)
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100 CONTINUE
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PRINT 1020
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PRINT 1030, B
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C
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CALL DGTSV (N, NRHS, DLOWER, DIAG, DUPPER, B, LDB, INFO)
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IF (INFO .LT. 0) THEN
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PRINT 1040, INFO
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STOP 1
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ELSE IF (INFO .GT. 0) THEN
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PRINT 1050
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STOP 2
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END IF
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PRINT 1060
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PRINT 1030, B
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C
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1000 FORMAT (1X, 'A:')
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1010 FORMAT (5(3X, F5.2))
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1020 FORMAT (/1X, 'b:')
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1030 FORMAT (1X, F8.2)
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1040 FORMAT (1X, 'Illegal argument to DGTSV, argument #', I2)
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1050 FORMAT (1X, 'A is singular to working precision.')
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1060 FORMAT (/1X, 'x:')
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C
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END
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