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

6       DORGQL - an M-by-N real matrix Q with orthonormal columns,
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SYNOPSIS

9       SUBROUTINE DORGQL( M, N, K, A, LDA, TAU, WORK, LWORK, INFO )
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11           INTEGER        INFO, K, LDA, LWORK, M, N
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13           DOUBLE         PRECISION A( LDA, * ), TAU( * ), WORK( * )
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PURPOSE

16       DORGQL  generates  an  M-by-N  real  matrix Q with orthonormal columns,
17       which is defined as the last N columns of a  product  of  K  elementary
18       reflectors of order M
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20             Q  =  H(k) . . . H(2) H(1)
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22       as returned by DGEQLF.
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ARGUMENTS

26       M       (input) INTEGER
27               The number of rows of the matrix Q. M >= 0.
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29       N       (input) INTEGER
30               The number of columns of the matrix Q. M >= N >= 0.
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32       K       (input) INTEGER
33               The  number  of elementary reflectors whose product defines the
34               matrix Q. N >= K >= 0.
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36       A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
37               On entry, the (n-k+i)-th column must contain the  vector  which
38               defines  the  elementary  reflector H(i), for i = 1,2,...,k, as
39               returned by DGEQLF in the last k columns of its array  argument
40               A.  On exit, the M-by-N matrix Q.
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42       LDA     (input) INTEGER
43               The first dimension of the array A. LDA >= max(1,M).
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45       TAU     (input) DOUBLE PRECISION array, dimension (K)
46               TAU(i) must contain the scalar factor of the elementary reflec‐
47               tor H(i), as returned by DGEQLF.
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49       WORK      (workspace/output)   DOUBLE   PRECISION   array,    dimension
50       (MAX(1,LWORK))
51               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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53       LWORK   (input) INTEGER
54               The  dimension of the array WORK. LWORK >= max(1,N).  For opti‐
55               mum performance LWORK >= N*NB, where NB is the  optimal  block‐
56               size.
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58               If  LWORK  = -1, then a workspace query is assumed; the routine
59               only calculates the optimal size of  the  WORK  array,  returns
60               this  value  as the first entry of the WORK array, and no error
61               message related to LWORK is issued by XERBLA.
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63       INFO    (output) INTEGER
64               = 0:  successful exit
65               < 0:  if INFO = -i, the i-th argument has an illegal value
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69 LAPACK routine (version 3.1)    November 2006                       DORGQL(1)