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PROGRAM TEST
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IMPLICIT NONE
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C
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INTEGER LDA, LDAF, LDB, LDIWRK, LDWORK, LDX
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INTEGER N, NRHS
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PARAMETER (N = 4)
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PARAMETER (LDA = (N * (N + 1)) / 2)
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PARAMETER (LDAF = LDA)
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PARAMETER (LDB = N)
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PARAMETER (LDIWRK = N)
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PARAMETER (LDX = N)
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PARAMETER (LDWORK = 3 * N)
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PARAMETER (NRHS = 1)
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C
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DOUBLE PRECISION A(LDA), AF(LDAF), B(LDB,NRHS), BERR(NRHS)
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DOUBLE PRECISION FERR(NRHS), RCOND, WORK(LDWORK)
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DOUBLE PRECISION X(LDX,NRHS)
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INTEGER I, INFO, IPIVOT(N), IWORK(LDIWRK)
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C
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EXTERNAL DSPSVX
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C
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C Initialize the array A to store in packed symmetric form
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C the 4x4 symmetric matrix A shown below. Initialize the
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C array B to store the right hand side vector b shown below.
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C
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C 2 -1 0 0 6
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C A = -1 2 -1 0 b = 12
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C 0 -1 2 -1 12
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C 0 0 -1 2 6
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C
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DATA A / 2.0D0, -1.0D0, 2.0D0, 0.0D0, -1.0D0, 2.0D0,
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$ 0.0D0, 0.0D0, -1.0D0, 2.0D0 /
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DATA B / 6.0D0, 1.2D1, 1.2D1, 6.0D0 /
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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(1), A(2), A(4), A(7)
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PRINT 1010, A(2), A(3), A(5), A(8)
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PRINT 1010, A(4), A(5), A(6), A(9)
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PRINT 1010, A(7), A(8), A(9), A(10)
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PRINT 1020
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PRINT 1030, B
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C
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C Solve Ax=b and print the solution.
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C
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CALL DSPSVX ('NOT FACTORED A', 'UPPER TRIANGLE OF A STORED',
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$ N, NRHS, A, AF, IPIVOT, B, LDB, X, LDX, RCOND,
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$ FERR, BERR, WORK, IWORK, INFO)
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IF (INFO .NE. 0) THEN
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PRINT 1040, INFO
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IF (INFO .EQ. (N + 1)) THEN
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PRINT 1050
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STOP 1
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END IF
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STOP 2
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END IF
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PRINT 1060
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PRINT 1030, X
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PRINT 1070, 1.0D0 / RCOND
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PRINT 1080, (I, BERR(I), I = 1, NRHS)
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PRINT 1090, (I, FERR(I), I = 1, NRHS)
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C
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1000 FORMAT (1X, 'A:')
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1010 FORMAT (4(3X, F6.3))
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1020 FORMAT (/1X, 'b:')
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1030 FORMAT (1X, F6.2)
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1040 FORMAT (1X, 'Error solving Ax=b, INFO = ', I5)
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1050 FORMAT (1X, 'Matrix is singular to working precision.')
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1060 FORMAT (/1X, 'x:')
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1070 FORMAT (/1X, 'Estimated condition number of A: ', F7.2)
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1080 FORMAT (/1X, 'Backward error for system #', I1, ': ', E12.6)
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1090 FORMAT (1X, 'Forward error for system #', I1, ': ', E12.6)
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C
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END
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