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SRC/sorm22.f(3) LAPACK SRC/sorm22.f(3)

SRC/sorm22.f


subroutine sorm22 (side, trans, m, n, n1, n2, q, ldq, c, ldc, work, lwork, info)
SORM22 multiplies a general matrix by a banded orthogonal matrix.

SORM22 multiplies a general matrix by a banded orthogonal matrix.

Purpose


SORM22 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
where Q is a real orthogonal matrix of order NQ, with NQ = M if
SIDE = 'L' and NQ = N if SIDE = 'R'.
The orthogonal matrix Q processes a 2-by-2 block structure
[ Q11 Q12 ]
Q = [ ]
[ Q21 Q22 ],
where Q12 is an N1-by-N1 lower triangular matrix and Q21 is an
N2-by-N2 upper triangular matrix.

Parameters

SIDE


SIDE is CHARACTER*1
= 'L': apply Q or Q**T from the Left;
= 'R': apply Q or Q**T from the Right.

TRANS


TRANS is CHARACTER*1
= 'N': apply Q (No transpose);
= 'C': apply Q**T (Conjugate transpose).

M


M is INTEGER
The number of rows of the matrix C. M >= 0.

N


N is INTEGER
The number of columns of the matrix C. N >= 0.

N1
N2


N1 is INTEGER
N2 is INTEGER
The dimension of Q12 and Q21, respectively. N1, N2 >= 0.
The following requirement must be satisfied:
N1 + N2 = M if SIDE = 'L' and N1 + N2 = N if SIDE = 'R'.

Q


Q is REAL array, dimension
(LDQ,M) if SIDE = 'L'
(LDQ,N) if SIDE = 'R'

LDQ


LDQ is INTEGER
The leading dimension of the array Q.
LDQ >= max(1,M) if SIDE = 'L'; LDQ >= max(1,N) if SIDE = 'R'.

C


C is 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.

LDC


LDC is INTEGER
The leading dimension of the array C. LDC >= max(1,M).

WORK


WORK is REAL array, dimension (MAX(1,LWORK))
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK


LWORK is 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 >= M*N.
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


INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 161 of file sorm22.f.

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Sun Jan 12 2025 15:13:31 Version 3.12.1

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