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PROGRAM TEST
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IMPLICIT NONE
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C
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INTEGER LDA, LDWORK, N, NDIAG
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PARAMETER (N = 4)
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PARAMETER (NDIAG = 1)
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PARAMETER (LDA = NDIAG + 1)
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PARAMETER (LDWORK = 3 * N)
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C
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DOUBLE PRECISION A(LDA,N), ANORM, RCOND, WORK(LDWORK)
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INTEGER ICOL, INFO, IROW, IWORK(N)
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C
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EXTERNAL DPBCON, DPBTRF
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INTRINSIC ABS
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C
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C Initialize the array A to store in symmetric banded form
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C the 4x4 symmetric positive definite matrix A with one
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C subdiagonal and one superdiagonal shown below.
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C
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C 2 -1 0 0
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C A = -1 2 -1 0
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C 0 -1 2 -1
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C 0 0 -1 2
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C
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DATA A / 8D8, 2.0D0, -1.0D0, 2.0D0,
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$ -1.0D0, 2.0D0, -1.0D0, 2.0D0 /
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C
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C Print the initial values of the arrays.
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C
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PRINT 1000
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PRINT 1010, A(2,1), A(1,2), 0.0D0, 0.0D0
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PRINT 1010, A(1,2), A(2,2), A(1,3), 0.0D0
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PRINT 1010, 0.0D0, A(1,3), A(2,3), A(1,4)
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PRINT 1010, 0.0D0, 0.0D0, A(1,4), A(2,4)
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PRINT 1020
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PRINT 1010, ((A(IROW,ICOL), ICOL = 1, N), IROW = 1, LDA)
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C
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C Cholesky factor A.
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C
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CALL DPBTRF ('UPPER TRIANGLE OF A STORED', N, NDIAG, A, LDA,
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$ INFO)
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IF (INFO .NE. 0) THEN
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PRINT 1030, INFO
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STOP 1
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END IF
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C
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C Compute and print the condition number of A.
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C
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ANORM = 3.0D0
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CALL DPBCON ('UPPER TRIANGLE FACTOR STORED', N, NDIAG, A,
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$ LDA, ANORM, RCOND, WORK, IWORK, INFO)
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IF (INFO .NE. 0) THEN
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PRINT 1040, ABS(INFO)
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STOP 2
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END IF
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PRINT 1050, 1.0D0 / RCOND
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C
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1000 FORMAT (1X, 'A in full form:')
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1010 FORMAT (4(3X, F6.3))
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1020 FORMAT (/1X, 'A in banded form: (* in unused elements)')
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1030 FORMAT (1X, 'Error factoring A, INFO = ', I5)
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1040 FORMAT (1X, 'Illegal argument to DPBCON, argument #', I2)
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1050 FORMAT (/1X, 'Estimated condition number of A = ', F8.4)
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C
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END
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