1DORM2R(1)                LAPACK routine (version 3.2)                DORM2R(1)
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NAME

6       DORM2R  -  overwrites  the general real m by n matrix C with   Q * C if
7       SIDE = 'L' and TRANS = 'N', or   Q'* C if SIDE = 'L' and TRANS  =  'T',
8       or   C * Q if SIDE = 'R' and TRANS = 'N', or   C * Q' if SIDE = 'R' and
9       TRANS = 'T',
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SYNOPSIS

12       SUBROUTINE DORM2R( SIDE, TRANS, M, N, K, A, LDA,  TAU,  C,  LDC,  WORK,
13                          INFO )
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15           CHARACTER      SIDE, TRANS
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17           INTEGER        INFO, K, LDA, LDC, M, N
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19           DOUBLE         PRECISION  A( LDA, * ), C( LDC, * ), TAU( * ), WORK(
20                          * )
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PURPOSE

23       DORM2R overwrites the general real m by n matrix C with where  Q  is  a
24       real  orthogonal  matrix defined as the product of k elementary reflec‐
25       tors
26             Q = H(1) H(2) . . . H(k)
27       as returned by DGEQRF. Q is of order m if SIDE = 'L' and of order n  if
28       SIDE = 'R'.
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ARGUMENTS

31       SIDE    (input) CHARACTER*1
32               = 'L': apply Q or Q' from the Left
33               = 'R': apply Q or Q' from the Right
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35       TRANS   (input) CHARACTER*1
36               = 'N': apply Q  (No transpose)
37               = 'T': apply Q' (Transpose)
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39       M       (input) INTEGER
40               The number of rows of the matrix C. M >= 0.
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42       N       (input) INTEGER
43               The number of columns of the matrix C. N >= 0.
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45       K       (input) INTEGER
46               The  number  of elementary reflectors whose product defines the
47               matrix Q.  If SIDE = 'L', M >= K >= 0; if SIDE = 'R', N >= K >=
48               0.
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50       A       (input) DOUBLE PRECISION array, dimension (LDA,K)
51               The  i-th column must contain the vector which defines the ele‐
52               mentary reflector H(i), for i = 1,2,...,k, as returned by  DGE‐
53               QRF in the first k columns of its array argument A.  A is modi‐
54               fied by the routine but restored on exit.
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56       LDA     (input) INTEGER
57               The leading dimension of the array A.  If SIDE =  'L',  LDA  >=
58               max(1,M); if SIDE = 'R', LDA >= max(1,N).
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60       TAU     (input) DOUBLE PRECISION array, dimension (K)
61               TAU(i) must contain the scalar factor of the elementary reflec‐
62               tor H(i), as returned by DGEQRF.
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64       C       (input/output) DOUBLE PRECISION array, dimension (LDC,N)
65               On entry, the m by n matrix C.  On exit, C  is  overwritten  by
66               Q*C or Q'*C or C*Q' or C*Q.
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68       LDC     (input) INTEGER
69               The leading dimension of the array C. LDC >= max(1,M).
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71       WORK    (workspace) DOUBLE PRECISION array, dimension
72               (N) if SIDE = 'L', (M) if SIDE = 'R'
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74       INFO    (output) INTEGER
75               = 0: successful exit
76               < 0: if INFO = -i, the i-th argument had an illegal value
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80 LAPACK routine (version 3.2)    November 2008                       DORM2R(1)
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