1DLARRC(1) LAPACK auxiliary routine (version 3.2) DLARRC(1)
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6 DLARRC - the number of eigenvalues of the symmetric tridiagonal matrix
7 T that are in the interval (VL,VU] if JOBT = 'T', and of L D L^T if
8 JOBT = 'L'
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11 SUBROUTINE DLARRC( JOBT, N, VL, VU, D, E, PIVMIN, EIGCNT, LCNT, RCNT,
12 INFO )
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14 CHARACTER JOBT
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16 INTEGER EIGCNT, INFO, LCNT, N, RCNT
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18 DOUBLE PRECISION PIVMIN, VL, VU
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20 DOUBLE PRECISION D( * ), E( * )
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23 Find the number of eigenvalues of the symmetric tridiagonal matrix T
24 that are in the interval (VL,VU] if JOBT = 'T', and of L D L^T if JOBT
25 = 'L'.
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28 JOBT (input) CHARACTER*1
29 = 'T': Compute Sturm count for matrix T.
30 = 'L': Compute Sturm count for matrix L D L^T.
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32 N (input) INTEGER
33 The order of the matrix. N > 0.
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35 VL (input) DOUBLE PRECISION
36 VU (input) DOUBLE PRECISION The lower and upper bounds for
37 the eigenvalues.
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39 D (input) DOUBLE PRECISION array, dimension (N)
40 JOBT = 'T': The N diagonal elements of the tridiagonal matrix
41 T.
42 JOBT = 'L': The N diagonal elements of the diagonal matrix D.
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44 E (input) DOUBLE PRECISION array, dimension (N)
45 JOBT = 'T': The N-1 offdiagonal elements of the matrix T.
46 JOBT = 'L': The N-1 offdiagonal elements of the matrix L.
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48 PIVMIN (input) DOUBLE PRECISION
49 The minimum pivot in the Sturm sequence for T.
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51 EIGCNT (output) INTEGER
52 The number of eigenvalues of the symmetric tridiagonal matrix T
53 that are in the interval (VL,VU]
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55 LCNT (output) INTEGER
56 RCNT (output) INTEGER The left and right negcounts of the
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59 INFO (output) INTEGER
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62 Based on contributions by
63 Beresford Parlett, University of California, Berkeley, USA
64 Jim Demmel, University of California, Berkeley, USA
65 Inderjit Dhillon, University of Texas, Austin, USA
66 Osni Marques, LBNL/NERSC, USA
67 Christof Voemel, University of California, Berkeley, USA
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71 LAPACK auxiliary routine (versionNo3v.e2m)ber 2008 DLARRC(1)