1SORGHR(1)                LAPACK routine (version 3.2)                SORGHR(1)
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NAME

6       SORGHR  -  generates a real orthogonal matrix Q which is defined as the
7       product of IHI-ILO elementary reflectors of order  N,  as  returned  by
8       SGEHRD
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SYNOPSIS

11       SUBROUTINE SORGHR( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO )
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13           INTEGER        IHI, ILO, INFO, LDA, LWORK, N
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15           REAL           A( LDA, * ), TAU( * ), WORK( * )
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PURPOSE

18       SORGHR  generates  a  real  orthogonal matrix Q which is defined as the
19       product of IHI-ILO elementary reflectors of order  N,  as  returned  by
20       SGEHRD: Q = H(ilo) H(ilo+1) . . . H(ihi-1).
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ARGUMENTS

23       N       (input) INTEGER
24               The order of the matrix Q. N >= 0.
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26       ILO     (input) INTEGER
27               IHI      (input)  INTEGER ILO and IHI must have the same values
28               as in the previous call of SGEHRD.  Q  is  equal  to  the  unit
29               matrix  except  in  the submatrix Q(ilo+1:ihi,ilo+1:ihi).  1 <=
30               ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
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32       A       (input/output) REAL array, dimension (LDA,N)
33               On entry, the vectors which define the  elementary  reflectors,
34               as  returned  by SGEHRD.  On exit, the N-by-N orthogonal matrix
35               Q.
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37       LDA     (input) INTEGER
38               The leading dimension of the array A. LDA >= max(1,N).
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40       TAU     (input) REAL array, dimension (N-1)
41               TAU(i) must contain the scalar factor of the elementary reflec‐
42               tor H(i), as returned by SGEHRD.
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44       WORK    (workspace/output) REAL array, dimension (MAX(1,LWORK))
45               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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47       LWORK   (input) INTEGER
48               The dimension of the array WORK. LWORK >= IHI-ILO.  For optimum
49               performance LWORK >= (IHI-ILO)*NB,  where  NB  is  the  optimal
50               blocksize.   If  LWORK = -1, then a workspace query is assumed;
51               the routine only calculates the optimal size of the WORK array,
52               returns this value as the first entry of the WORK array, and no
53               error message related to LWORK is issued by XERBLA.
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55       INFO    (output) INTEGER
56               = 0:  successful exit
57               < 0:  if INFO = -i, the i-th argument had an illegal value
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61 LAPACK routine (version 3.2)    November 2008                       SORGHR(1)