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PROGRAM TEST
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IMPLICIT NONE
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C
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INTEGER LDB, LDWORK, N, NRHS
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PARAMETER (N = 4)
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PARAMETER (LDB = 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 ANORM, DIAG(N), DLOWER(N-1), RCOND
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DOUBLE PRECISION WORK(LDWORK)
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INTEGER ICOL, INFO, IROW
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C
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EXTERNAL DPTCON, DPTTRF
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INTRINSIC ABS
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C
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C Initialize the arrays DIAG and DLOWER to store the diagonal
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C and first off diagonal of the matrix A shown below.
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C
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C 2 -1
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C -1 2 -1
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C A = -1 2 -1
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C 1 2 -1
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C
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DATA DIAG / 2.0D0, 2.0D0, 2.0D0, 2.0D0 /
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DATA DLOWER / -1.0D0, -1.0D0, -1.0D0 /
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C
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C Print the initial value of the arrays.
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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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$ (DLOWER(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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C
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C LDL factor A.
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C
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CALL DPTTRF (N, DIAG, DLOWER, INFO)
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IF (INFO .NE. 0) THEN
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PRINT 1020, INFO
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STOP 1
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END IF
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C
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C Estimate and print the condition number of A.
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C
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ANORM = 4.0D0
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CALL DPTCON (N, DIAG, DLOWER, ANORM, RCOND, WORK, INFO)
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IF (INFO .NE. 0) THEN
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PRINT 1030, ABS (INFO)
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STOP 2
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END IF
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PRINT 1040, 1.0D0 / RCOND
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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, 'Error factoring A, INFO = ', I5)
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1030 FORMAT (1X, 'Illegal argument to DPTCON, argument #', I2)
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1040 FORMAT (/1X, 'Estimated condition number of A: ', F6.2)
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C
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END
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