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authorjason <jason@8a072113-8704-0410-8d35-dd094bca7971>2008-10-28 01:38:50 +0000
committerjason <jason@8a072113-8704-0410-8d35-dd094bca7971>2008-10-28 01:38:50 +0000
commitbaba851215b44ac3b60b9248eb02bcce7eb76247 (patch)
tree8c0f5c006875532a30d4409f5e94b0f310ff00a7 /SRC/sormbr.f
Move LAPACK trunk into position.
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+ SUBROUTINE SORMBR( VECT, SIDE, TRANS, M, N, K, A, LDA, TAU, C,
+ $ LDC, WORK, LWORK, INFO )
+*
+* -- LAPACK routine (version 3.1) --
+* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
+* November 2006
+*
+* .. Scalar Arguments ..
+ CHARACTER SIDE, TRANS, VECT
+ INTEGER INFO, K, LDA, LDC, LWORK, M, N
+* ..
+* .. Array Arguments ..
+ REAL A( LDA, * ), C( LDC, * ), TAU( * ),
+ $ WORK( * )
+* ..
+*
+* Purpose
+* =======
+*
+* If VECT = 'Q', SORMBR overwrites the general real M-by-N matrix C
+* with
+* SIDE = 'L' SIDE = 'R'
+* TRANS = 'N': Q * C C * Q
+* TRANS = 'T': Q**T * C C * Q**T
+*
+* If VECT = 'P', SORMBR overwrites the general real M-by-N matrix C
+* with
+* SIDE = 'L' SIDE = 'R'
+* TRANS = 'N': P * C C * P
+* TRANS = 'T': P**T * C C * P**T
+*
+* Here Q and P**T are the orthogonal matrices determined by SGEBRD when
+* reducing a real matrix A to bidiagonal form: A = Q * B * P**T. Q and
+* P**T are defined as products of elementary reflectors H(i) and G(i)
+* respectively.
+*
+* Let nq = m if SIDE = 'L' and nq = n if SIDE = 'R'. Thus nq is the
+* order of the orthogonal matrix Q or P**T that is applied.
+*
+* If VECT = 'Q', A is assumed to have been an NQ-by-K matrix:
+* if nq >= k, Q = H(1) H(2) . . . H(k);
+* if nq < k, Q = H(1) H(2) . . . H(nq-1).
+*
+* If VECT = 'P', A is assumed to have been a K-by-NQ matrix:
+* if k < nq, P = G(1) G(2) . . . G(k);
+* if k >= nq, P = G(1) G(2) . . . G(nq-1).
+*
+* Arguments
+* =========
+*
+* VECT (input) CHARACTER*1
+* = 'Q': apply Q or Q**T;
+* = 'P': apply P or P**T.
+*
+* SIDE (input) CHARACTER*1
+* = 'L': apply Q, Q**T, P or P**T from the Left;
+* = 'R': apply Q, Q**T, P or P**T from the Right.
+*
+* TRANS (input) CHARACTER*1
+* = 'N': No transpose, apply Q or P;
+* = 'T': Transpose, apply Q**T or P**T.
+*
+* M (input) INTEGER
+* The number of rows of the matrix C. M >= 0.
+*
+* N (input) INTEGER
+* The number of columns of the matrix C. N >= 0.
+*
+* K (input) INTEGER
+* If VECT = 'Q', the number of columns in the original
+* matrix reduced by SGEBRD.
+* If VECT = 'P', the number of rows in the original
+* matrix reduced by SGEBRD.
+* K >= 0.
+*
+* A (input) REAL array, dimension
+* (LDA,min(nq,K)) if VECT = 'Q'
+* (LDA,nq) if VECT = 'P'
+* The vectors which define the elementary reflectors H(i) and
+* G(i), whose products determine the matrices Q and P, as
+* returned by SGEBRD.
+*
+* LDA (input) INTEGER
+* The leading dimension of the array A.
+* If VECT = 'Q', LDA >= max(1,nq);
+* if VECT = 'P', LDA >= max(1,min(nq,K)).
+*
+* TAU (input) REAL array, dimension (min(nq,K))
+* TAU(i) must contain the scalar factor of the elementary
+* reflector H(i) or G(i) which determines Q or P, as returned
+* by SGEBRD in the array argument TAUQ or TAUP.
+*
+* C (input/output) REAL array, dimension (LDC,N)
+* On entry, the M-by-N matrix C.
+* On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q
+* or P*C or P**T*C or C*P or C*P**T.
+*
+* LDC (input) INTEGER
+* The leading dimension of the array C. LDC >= max(1,M).
+*
+* WORK (workspace/output) REAL array, dimension (MAX(1,LWORK))
+* On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
+*
+* LWORK (input) INTEGER
+* The dimension of the array WORK.
+* If SIDE = 'L', LWORK >= max(1,N);
+* if SIDE = 'R', LWORK >= max(1,M).
+* For optimum performance LWORK >= N*NB if SIDE = 'L', and
+* LWORK >= M*NB if SIDE = 'R', where NB is the optimal
+* blocksize.
+*
+* If LWORK = -1, then a workspace query is assumed; the routine
+* only calculates the optimal size of the WORK array, returns
+* this value as the first entry of the WORK array, and no error
+* message related to LWORK is issued by XERBLA.
+*
+* INFO (output) INTEGER
+* = 0: successful exit
+* < 0: if INFO = -i, the i-th argument had an illegal value
+*
+* =====================================================================
+*
+* .. Local Scalars ..
+ LOGICAL APPLYQ, LEFT, LQUERY, NOTRAN
+ CHARACTER TRANST
+ INTEGER I1, I2, IINFO, LWKOPT, MI, NB, NI, NQ, NW
+* ..
+* .. External Functions ..
+ LOGICAL LSAME
+ INTEGER ILAENV
+ EXTERNAL ILAENV, LSAME
+* ..
+* .. External Subroutines ..
+ EXTERNAL SORMLQ, SORMQR, XERBLA
+* ..
+* .. Intrinsic Functions ..
+ INTRINSIC MAX, MIN
+* ..
+* .. Executable Statements ..
+*
+* Test the input arguments
+*
+ INFO = 0
+ APPLYQ = LSAME( VECT, 'Q' )
+ LEFT = LSAME( SIDE, 'L' )
+ NOTRAN = LSAME( TRANS, 'N' )
+ LQUERY = ( LWORK.EQ.-1 )
+*
+* NQ is the order of Q or P and NW is the minimum dimension of WORK
+*
+ IF( LEFT ) THEN
+ NQ = M
+ NW = N
+ ELSE
+ NQ = N
+ NW = M
+ END IF
+ IF( .NOT.APPLYQ .AND. .NOT.LSAME( VECT, 'P' ) ) THEN
+ INFO = -1
+ ELSE IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
+ INFO = -2
+ ELSE IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'T' ) ) THEN
+ INFO = -3
+ ELSE IF( M.LT.0 ) THEN
+ INFO = -4
+ ELSE IF( N.LT.0 ) THEN
+ INFO = -5
+ ELSE IF( K.LT.0 ) THEN
+ INFO = -6
+ ELSE IF( ( APPLYQ .AND. LDA.LT.MAX( 1, NQ ) ) .OR.
+ $ ( .NOT.APPLYQ .AND. LDA.LT.MAX( 1, MIN( NQ, K ) ) ) )
+ $ THEN
+ INFO = -8
+ ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
+ INFO = -11
+ ELSE IF( LWORK.LT.MAX( 1, NW ) .AND. .NOT.LQUERY ) THEN
+ INFO = -13
+ END IF
+*
+ IF( INFO.EQ.0 ) THEN
+ IF( APPLYQ ) THEN
+ IF( LEFT ) THEN
+ NB = ILAENV( 1, 'SORMQR', SIDE // TRANS, M-1, N, M-1,
+ $ -1 )
+ ELSE
+ NB = ILAENV( 1, 'SORMQR', SIDE // TRANS, M, N-1, N-1,
+ $ -1 )
+ END IF
+ ELSE
+ IF( LEFT ) THEN
+ NB = ILAENV( 1, 'SORMLQ', SIDE // TRANS, M-1, N, M-1,
+ $ -1 )
+ ELSE
+ NB = ILAENV( 1, 'SORMLQ', SIDE // TRANS, M, N-1, N-1,
+ $ -1 )
+ END IF
+ END IF
+ LWKOPT = MAX( 1, NW )*NB
+ WORK( 1 ) = LWKOPT
+ END IF
+*
+ IF( INFO.NE.0 ) THEN
+ CALL XERBLA( 'SORMBR', -INFO )
+ RETURN
+ ELSE IF( LQUERY ) THEN
+ RETURN
+ END IF
+*
+* Quick return if possible
+*
+ WORK( 1 ) = 1
+ IF( M.EQ.0 .OR. N.EQ.0 )
+ $ RETURN
+*
+ IF( APPLYQ ) THEN
+*
+* Apply Q
+*
+ IF( NQ.GE.K ) THEN
+*
+* Q was determined by a call to SGEBRD with nq >= k
+*
+ CALL SORMQR( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
+ $ WORK, LWORK, IINFO )
+ ELSE IF( NQ.GT.1 ) THEN
+*
+* Q was determined by a call to SGEBRD with nq < k
+*
+ IF( LEFT ) THEN
+ MI = M - 1
+ NI = N
+ I1 = 2
+ I2 = 1
+ ELSE
+ MI = M
+ NI = N - 1
+ I1 = 1
+ I2 = 2
+ END IF
+ CALL SORMQR( SIDE, TRANS, MI, NI, NQ-1, A( 2, 1 ), LDA, TAU,
+ $ C( I1, I2 ), LDC, WORK, LWORK, IINFO )
+ END IF
+ ELSE
+*
+* Apply P
+*
+ IF( NOTRAN ) THEN
+ TRANST = 'T'
+ ELSE
+ TRANST = 'N'
+ END IF
+ IF( NQ.GT.K ) THEN
+*
+* P was determined by a call to SGEBRD with nq > k
+*
+ CALL SORMLQ( SIDE, TRANST, M, N, K, A, LDA, TAU, C, LDC,
+ $ WORK, LWORK, IINFO )
+ ELSE IF( NQ.GT.1 ) THEN
+*
+* P was determined by a call to SGEBRD with nq <= k
+*
+ IF( LEFT ) THEN
+ MI = M - 1
+ NI = N
+ I1 = 2
+ I2 = 1
+ ELSE
+ MI = M
+ NI = N - 1
+ I1 = 1
+ I2 = 2
+ END IF
+ CALL SORMLQ( SIDE, TRANST, MI, NI, NQ-1, A( 1, 2 ), LDA,
+ $ TAU, C( I1, I2 ), LDC, WORK, LWORK, IINFO )
+ END IF
+ END IF
+ WORK( 1 ) = LWKOPT
+ RETURN
+*
+* End of SORMBR
+*
+ END