1SORGTR(1)                LAPACK routine (version 3.1)                SORGTR(1)
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NAME

6       SORGTR  - a real orthogonal matrix Q which is defined as the product of
7       n-1 elementary reflectors of order N, as returned by SSYTRD
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SYNOPSIS

10       SUBROUTINE SORGTR( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO )
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12           CHARACTER      UPLO
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14           INTEGER        INFO, LDA, LWORK, N
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16           REAL           A( LDA, * ), TAU( * ), WORK( * )
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PURPOSE

19       SORGTR generates a real orthogonal matrix Q which  is  defined  as  the
20       product of n-1 elementary reflectors of order N, as returned by SSYTRD:
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22       if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
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24       if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
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ARGUMENTS

28       UPLO    (input) CHARACTER*1
29               =  'U': Upper triangle of A contains elementary reflectors from
30               SSYTRD; = 'L': Lower triangle of A contains elementary  reflec‐
31               tors from SSYTRD.
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33       N       (input) INTEGER
34               The order of the matrix Q. N >= 0.
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36       A       (input/output) REAL array, dimension (LDA,N)
37               On  entry,  the vectors which define the elementary reflectors,
38               as returned by SSYTRD.  On exit, the N-by-N  orthogonal  matrix
39               Q.
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41       LDA     (input) INTEGER
42               The leading dimension of the array A. LDA >= max(1,N).
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44       TAU     (input) REAL array, dimension (N-1)
45               TAU(i) must contain the scalar factor of the elementary reflec‐
46               tor H(i), as returned by SSYTRD.
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48       WORK    (workspace/output) REAL array, dimension (MAX(1,LWORK))
49               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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51       LWORK   (input) INTEGER
52               The dimension of the array  WORK.  LWORK  >=  max(1,N-1).   For
53               optimum  performance LWORK >= (N-1)*NB, where NB is the optimal
54               blocksize.
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56               If LWORK = -1, then a workspace query is assumed;  the  routine
57               only  calculates  the  optimal  size of the WORK array, returns
58               this value as the first entry of the WORK array, and  no  error
59               message related to LWORK is issued by XERBLA.
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61       INFO    (output) INTEGER
62               = 0:  successful exit
63               < 0:  if INFO = -i, the i-th argument had an illegal value
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67 LAPACK routine (version 3.1)    November 2006                       SORGTR(1)
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