1
SUBROUTINE DORMQR( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
4
* -- LAPACK routine (version 2.0) --
5
* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
6
* Courant Institute, Argonne National Lab, and Rice University
9
* .. Scalar Arguments ..
11
INTEGER INFO, K, LDA, LDC, LWORK, M, N
13
* .. Array Arguments ..
14
DOUBLE PRECISION A( LDA, * ), C( LDC, * ), TAU( * ),
21
* DORMQR overwrites the general real M-by-N matrix C with
23
* SIDE = 'L' SIDE = 'R'
24
* TRANS = 'N': Q * C C * Q
25
* TRANS = 'T': Q**T * C C * Q**T
27
* where Q is a real orthogonal matrix defined as the product of k
28
* elementary reflectors
30
* Q = H(1) H(2) . . . H(k)
32
* as returned by DGEQRF. Q is of order M if SIDE = 'L' and of order N
38
* SIDE (input) CHARACTER*1
39
* = 'L': apply Q or Q**T from the Left;
40
* = 'R': apply Q or Q**T from the Right.
42
* TRANS (input) CHARACTER*1
43
* = 'N': No transpose, apply Q;
44
* = 'T': Transpose, apply Q**T.
47
* The number of rows of the matrix C. M >= 0.
50
* The number of columns of the matrix C. N >= 0.
53
* The number of elementary reflectors whose product defines
55
* If SIDE = 'L', M >= K >= 0;
56
* if SIDE = 'R', N >= K >= 0.
58
* A (input) DOUBLE PRECISION array, dimension (LDA,K)
59
* The i-th column must contain the vector which defines the
60
* elementary reflector H(i), for i = 1,2,...,k, as returned by
61
* DGEQRF in the first k columns of its array argument A.
62
* A is modified by the routine but restored on exit.
65
* The leading dimension of the array A.
66
* If SIDE = 'L', LDA >= max(1,M);
67
* if SIDE = 'R', LDA >= max(1,N).
69
* TAU (input) DOUBLE PRECISION array, dimension (K)
70
* TAU(i) must contain the scalar factor of the elementary
71
* reflector H(i), as returned by DGEQRF.
73
* C (input/output) DOUBLE PRECISION array, dimension (LDC,N)
74
* On entry, the M-by-N matrix C.
75
* On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.
78
* The leading dimension of the array C. LDC >= max(1,M).
80
* WORK (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
81
* On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
83
* LWORK (input) INTEGER
84
* The dimension of the array WORK.
85
* If SIDE = 'L', LWORK >= max(1,N);
86
* if SIDE = 'R', LWORK >= max(1,M).
87
* For optimum performance LWORK >= N*NB if SIDE = 'L', and
88
* LWORK >= M*NB if SIDE = 'R', where NB is the optimal
91
* INFO (output) INTEGER
92
* = 0: successful exit
93
* < 0: if INFO = -i, the i-th argument had an illegal value
95
* =====================================================================
99
PARAMETER ( NBMAX = 64, LDT = NBMAX+1 )
101
* .. Local Scalars ..
103
INTEGER I, I1, I2, I3, IB, IC, IINFO, IWS, JC, LDWORK,
104
$ MI, NB, NBMIN, NI, NQ, NW
107
DOUBLE PRECISION T( LDT, NBMAX )
109
* .. External Functions ..
112
EXTERNAL LSAME, ILAENV
114
* .. External Subroutines ..
115
EXTERNAL DLARFB, DLARFT, DORM2R, XERBLA
117
* .. Intrinsic Functions ..
120
* .. Executable Statements ..
122
* Test the input arguments
125
LEFT = LSAME( SIDE, 'L' )
126
NOTRAN = LSAME( TRANS, 'N' )
128
* NQ is the order of Q and NW is the minimum dimension of WORK
137
IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
139
ELSE IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'T' ) ) THEN
141
ELSE IF( M.LT.0 ) THEN
143
ELSE IF( N.LT.0 ) THEN
145
ELSE IF( K.LT.0 .OR. K.GT.NQ ) THEN
147
ELSE IF( LDA.LT.MAX( 1, NQ ) ) THEN
149
ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
151
ELSE IF( LWORK.LT.MAX( 1, NW ) ) THEN
155
CALL XERBLA( 'DORMQR', -INFO )
159
* Quick return if possible
161
IF( M.EQ.0 .OR. N.EQ.0 .OR. K.EQ.0 ) THEN
166
* Determine the block size. NB may be at most NBMAX, where NBMAX
167
* is used to define the local array T.
169
NB = MIN( NBMAX, ILAENV( 1, 'DORMQR', SIDE // TRANS, M, N, K,
173
IF( NB.GT.1 .AND. NB.LT.K ) THEN
175
IF( LWORK.LT.IWS ) THEN
177
NBMIN = MAX( 2, ILAENV( 2, 'DORMQR', SIDE // TRANS, M, N, K,
184
IF( NB.LT.NBMIN .OR. NB.GE.K ) THEN
188
CALL DORM2R( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK,
194
IF( ( LEFT .AND. .NOT.NOTRAN ) .OR.
195
$ ( .NOT.LEFT .AND. NOTRAN ) ) THEN
200
I1 = ( ( K-1 ) / NB )*NB + 1
214
IB = MIN( NB, K-I+1 )
216
* Form the triangular factor of the block reflector
217
* H = H(i) H(i+1) . . . H(i+ib-1)
219
CALL DLARFT( 'Forward', 'Columnwise', NQ-I+1, IB, A( I, I ),
220
$ LDA, TAU( I ), T, LDT )
223
* H or H' is applied to C(i:m,1:n)
229
* H or H' is applied to C(1:m,i:n)
237
CALL DLARFB( SIDE, TRANS, 'Forward', 'Columnwise', MI, NI,
238
$ IB, A( I, I ), LDA, T, LDT, C( IC, JC ), LDC,