Library Functions Manual

NAME¶

lamtsqr - lamtsqr: multiply by Q from latsqr

SYNOPSIS¶

Functions¶

subroutine CLAMTSQR (side, trans, m, n, k, mb, nb, a, lda, t, ldt, c, ldc, work, lwork, info)
CLAMTSQR subroutine DLAMTSQR (side, trans, m, n, k, mb, nb, a, lda, t, ldt, c, ldc, work, lwork, info)
DLAMTSQR subroutine SLAMTSQR (side, trans, m, n, k, mb, nb, a, lda, t, ldt, c, ldc, work, lwork, info)
SLAMTSQR subroutine ZLAMTSQR (side, trans, m, n, k, mb, nb, a, lda, t, ldt, c, ldc, work, lwork, info)
ZLAMTSQR

Detailed Description¶

Function Documentation¶

subroutine CLAMTSQR (character side, character trans, integer m, integer n, integer k, integer mb, integer nb, complex, dimension( lda, * ) a, integer lda, complex, dimension( ldt, * ) t, integer ldt, complex, dimension(ldc, * ) c, integer ldc, complex, dimension( * ) work, integer lwork, integer info)¶

CLAMTSQR

Purpose:

!>
!>      CLAMTSQR overwrites the general complex M-by-N matrix C with
!>
!>
!>                 SIDE = 'L'     SIDE = 'R'
!> TRANS = 'N':      Q * C          C * Q
!> TRANS = 'C':      Q**H * C       C * Q**H
!>      where Q is a complex unitary matrix defined as the product
!>      of blocked elementary reflectors computed by tall skinny
!>      QR factorization (CLATSQR)
!>

Parameters

SIDE

!>          SIDE is CHARACTER*1
!>          = 'L': apply Q or Q**H from the Left;
!>          = 'R': apply Q or Q**H from the Right.
!>

TRANS

!>          TRANS is CHARACTER*1
!>          = 'N':  No transpose, apply Q;
!>          = 'C':  Conjugate Transpose, apply Q**H.
!>

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

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

!>          K is INTEGER
!>          The number of elementary reflectors whose product defines
!>          the matrix Q. M >= K >= 0;
!>
!>

!>          MB is INTEGER
!>          The block size to be used in the blocked QR.
!>          MB > N. (must be the same as CLATSQR)
!>

!>          NB is INTEGER
!>          The column block size to be used in the blocked QR.
!>          N >= NB >= 1.
!>

!>          A is COMPLEX array, dimension (LDA,K)
!>          The i-th column must contain the vector which defines the
!>          blockedelementary reflector H(i), for i = 1,2,...,k, as
!>          returned by CLATSQR in the first k columns of
!>          its array argument A.
!>

LDA

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

!>          T is COMPLEX array, dimension
!>          ( N * Number of blocks(CEIL(M-K/MB-K)),
!>          The blocked upper triangular block reflectors stored in compact form
!>          as a sequence of upper triangular blocks.  See below
!>          for further details.
!>

LDT

!>          LDT is INTEGER
!>          The leading dimension of the array T.  LDT >= NB.
!>

!>          C is COMPLEX array, dimension (LDC,N)
!>          On entry, the M-by-N matrix C.
!>          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
!>

LDC

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

WORK

!>         (workspace) COMPLEX array, dimension (MAX(1,LWORK))
!>
!>

LWORK

!>          LWORK is INTEGER
!>          The dimension of the array WORK.
!>
!>          If SIDE = 'L', LWORK >= max(1,N)*NB;
!>          if SIDE = 'R', LWORK >= max(1,MB)*NB.
!>          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.

Further Details:

!> Tall-Skinny QR (TSQR) performs QR by a sequence of unitary transformations,
!> representing Q as a product of other unitary matrices
!>   Q = Q(1) * Q(2) * . . . * Q(k)
!> where each Q(i) zeros out subdiagonal entries of a block of MB rows of A:
!>   Q(1) zeros out the subdiagonal entries of rows 1:MB of A
!>   Q(2) zeros out the bottom MB-N rows of rows [1:N,MB+1:2*MB-N] of A
!>   Q(3) zeros out the bottom MB-N rows of rows [1:N,2*MB-N+1:3*MB-2*N] of A
!>   . . .
!>
!> Q(1) is computed by GEQRT, which represents Q(1) by Householder vectors
!> stored under the diagonal of rows 1:MB of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,1:N).
!> For more information see Further Details in GEQRT.
!>
!> Q(i) for i>1 is computed by TPQRT, which represents Q(i) by Householder vectors
!> stored in rows [(i-1)*(MB-N)+N+1:i*(MB-N)+N] of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,(i-1)*N+1:i*N).
!> The last Q(k) may use fewer rows.
!> For more information see Further Details in TPQRT.
!>
!> For more details of the overall algorithm, see the description of
!> Sequential TSQR in Section 2.2 of [1].
!>
!> [1] “Communication-Optimal Parallel and Sequential QR and LU Factorizations,”
!>     J. Demmel, L. Grigori, M. Hoemmen, J. Langou,
!>     SIAM J. Sci. Comput, vol. 34, no. 1, 2012
!>

Definition at line 197 of file clamtsqr.f.

subroutine DLAMTSQR (character side, character trans, integer m, integer n, integer k, integer mb, integer nb, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldt, * ) t, integer ldt, double precision, dimension(ldc, * ) c, integer ldc, double precision, dimension( * ) work, integer lwork, integer info)¶

DLAMTSQR

Purpose:

!>
!>      DLAMTSQR 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 defined as the product
!>      of blocked elementary reflectors computed by tall skinny
!>      QR factorization (DLATSQR)
!>

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':  No transpose, apply Q;
!>          = 'T':  Transpose, apply Q**T.
!>

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

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

!>          K is INTEGER
!>          The number of elementary reflectors whose product defines
!>          the matrix Q. M >= K >= 0;
!>
!>

!>          MB is INTEGER
!>          The block size to be used in the blocked QR.
!>          MB > N. (must be the same as DLATSQR)
!>

!>          NB is INTEGER
!>          The column block size to be used in the blocked QR.
!>          N >= NB >= 1.
!>

!>          A is DOUBLE PRECISION array, dimension (LDA,K)
!>          The i-th column must contain the vector which defines the
!>          blockedelementary reflector H(i), for i = 1,2,...,k, as
!>          returned by DLATSQR in the first k columns of
!>          its array argument A.
!>

LDA

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

!>          T is DOUBLE PRECISION array, dimension
!>          ( N * Number of blocks(CEIL(M-K/MB-K)),
!>          The blocked upper triangular block reflectors stored in compact form
!>          as a sequence of upper triangular blocks.  See below
!>          for further details.
!>

LDT

!>          LDT is INTEGER
!>          The leading dimension of the array T.  LDT >= NB.
!>

!>          C is DOUBLE PRECISION 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

!>         (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK))
!>
!>

LWORK

!>          LWORK is INTEGER
!>          The dimension of the array WORK.
!>
!>          If SIDE = 'L', LWORK >= max(1,N)*NB;
!>          if SIDE = 'R', LWORK >= max(1,MB)*NB.
!>          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.

Further Details:

!> Tall-Skinny QR (TSQR) performs QR by a sequence of orthogonal transformations,
!> representing Q as a product of other orthogonal matrices
!>   Q = Q(1) * Q(2) * . . . * Q(k)
!> where each Q(i) zeros out subdiagonal entries of a block of MB rows of A:
!>   Q(1) zeros out the subdiagonal entries of rows 1:MB of A
!>   Q(2) zeros out the bottom MB-N rows of rows [1:N,MB+1:2*MB-N] of A
!>   Q(3) zeros out the bottom MB-N rows of rows [1:N,2*MB-N+1:3*MB-2*N] of A
!>   . . .
!>
!> Q(1) is computed by GEQRT, which represents Q(1) by Householder vectors
!> stored under the diagonal of rows 1:MB of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,1:N).
!> For more information see Further Details in GEQRT.
!>
!> Q(i) for i>1 is computed by TPQRT, which represents Q(i) by Householder vectors
!> stored in rows [(i-1)*(MB-N)+N+1:i*(MB-N)+N] of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,(i-1)*N+1:i*N).
!> The last Q(k) may use fewer rows.
!> For more information see Further Details in TPQRT.
!>
!> For more details of the overall algorithm, see the description of
!> Sequential TSQR in Section 2.2 of [1].
!>
!> [1] “Communication-Optimal Parallel and Sequential QR and LU Factorizations,”
!>     J. Demmel, L. Grigori, M. Hoemmen, J. Langou,
!>     SIAM J. Sci. Comput, vol. 34, no. 1, 2012
!>

Definition at line 197 of file dlamtsqr.f.

subroutine SLAMTSQR (character side, character trans, integer m, integer n, integer k, integer mb, integer nb, real, dimension( lda, * ) a, integer lda, real, dimension( ldt, * ) t, integer ldt, real, dimension(ldc, * ) c, integer ldc, real, dimension( * ) work, integer lwork, integer info)¶

SLAMTSQR

Purpose:

!>
!>      SLAMTSQR 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 defined as the product
!>      of blocked elementary reflectors computed by tall skinny
!>      QR factorization (SLATSQR)
!>

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':  No transpose, apply Q;
!>          = 'T':  Transpose, apply Q**T.
!>

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

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

!>          K is INTEGER
!>          The number of elementary reflectors whose product defines
!>          the matrix Q. M >= K >= 0;
!>
!>

!>          MB is INTEGER
!>          The block size to be used in the blocked QR.
!>          MB > N. (must be the same as SLATSQR)
!>

!>          NB is INTEGER
!>          The column block size to be used in the blocked QR.
!>          N >= NB >= 1.
!>

!>          A is REAL array, dimension (LDA,K)
!>          The i-th column must contain the vector which defines the
!>          blockedelementary reflector H(i), for i = 1,2,...,k, as
!>          returned by SLATSQR in the first k columns of
!>          its array argument A.
!>

LDA

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

!>          T is REAL array, dimension
!>          ( N * Number of blocks(CEIL(M-K/MB-K)),
!>          The blocked upper triangular block reflectors stored in compact form
!>          as a sequence of upper triangular blocks.  See below
!>          for further details.
!>

LDT

!>          LDT is INTEGER
!>          The leading dimension of the array T.  LDT >= NB.
!>

!>          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

!>         (workspace) REAL array, dimension (MAX(1,LWORK))
!>
!>

LWORK

!>          LWORK is INTEGER
!>          The dimension of the array WORK.
!>
!>          If SIDE = 'L', LWORK >= max(1,N)*NB;
!>          if SIDE = 'R', LWORK >= max(1,MB)*NB.
!>          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.

Further Details:

!> Tall-Skinny QR (TSQR) performs QR by a sequence of orthogonal transformations,
!> representing Q as a product of other orthogonal matrices
!>   Q = Q(1) * Q(2) * . . . * Q(k)
!> where each Q(i) zeros out subdiagonal entries of a block of MB rows of A:
!>   Q(1) zeros out the subdiagonal entries of rows 1:MB of A
!>   Q(2) zeros out the bottom MB-N rows of rows [1:N,MB+1:2*MB-N] of A
!>   Q(3) zeros out the bottom MB-N rows of rows [1:N,2*MB-N+1:3*MB-2*N] of A
!>   . . .
!>
!> Q(1) is computed by GEQRT, which represents Q(1) by Householder vectors
!> stored under the diagonal of rows 1:MB of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,1:N).
!> For more information see Further Details in GEQRT.
!>
!> Q(i) for i>1 is computed by TPQRT, which represents Q(i) by Householder vectors
!> stored in rows [(i-1)*(MB-N)+N+1:i*(MB-N)+N] of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,(i-1)*N+1:i*N).
!> The last Q(k) may use fewer rows.
!> For more information see Further Details in TPQRT.
!>
!> For more details of the overall algorithm, see the description of
!> Sequential TSQR in Section 2.2 of [1].
!>
!> [1] “Communication-Optimal Parallel and Sequential QR and LU Factorizations,”
!>     J. Demmel, L. Grigori, M. Hoemmen, J. Langou,
!>     SIAM J. Sci. Comput, vol. 34, no. 1, 2012
!>

Definition at line 197 of file slamtsqr.f.

subroutine ZLAMTSQR (character side, character trans, integer m, integer n, integer k, integer mb, integer nb, complex16, dimension( lda, ) a, integer lda, complex16, dimension( ldt, ) t, integer ldt, complex16, dimension(ldc, ) c, integer ldc, complex16, dimension( ) work, integer lwork, integer info)¶

ZLAMTSQR

Purpose:

!>
!>      ZLAMTSQR overwrites the general complex M-by-N matrix C with
!>
!>
!>                 SIDE = 'L'     SIDE = 'R'
!> TRANS = 'N':      Q * C          C * Q
!> TRANS = 'C':      Q**H * C       C * Q**H
!>      where Q is a complex unitary matrix defined as the product
!>      of blocked elementary reflectors computed by tall skinny
!>      QR factorization (ZLATSQR)
!>

Parameters

SIDE

!>          SIDE is CHARACTER*1
!>          = 'L': apply Q or Q**H from the Left;
!>          = 'R': apply Q or Q**H from the Right.
!>

TRANS

!>          TRANS is CHARACTER*1
!>          = 'N':  No transpose, apply Q;
!>          = 'C':  Conjugate Transpose, apply Q**H.
!>

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

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

!>          K is INTEGER
!>          The number of elementary reflectors whose product defines
!>          the matrix Q. M >= K >= 0;
!>
!>

!>          MB is INTEGER
!>          The block size to be used in the blocked QR.
!>          MB > N. (must be the same as ZLATSQR)
!>

!>          NB is INTEGER
!>          The column block size to be used in the blocked QR.
!>          N >= NB >= 1.
!>

!>          A is COMPLEX*16 array, dimension (LDA,K)
!>          The i-th column must contain the vector which defines the
!>          blockedelementary reflector H(i), for i = 1,2,...,k, as
!>          returned by ZLATSQR in the first k columns of
!>          its array argument A.
!>

LDA

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

!>          T is COMPLEX*16 array, dimension
!>          ( N * Number of blocks(CEIL(M-K/MB-K)),
!>          The blocked upper triangular block reflectors stored in compact form
!>          as a sequence of upper triangular blocks.  See below
!>          for further details.
!>

LDT

!>          LDT is INTEGER
!>          The leading dimension of the array T.  LDT >= NB.
!>

!>          C is COMPLEX*16 array, dimension (LDC,N)
!>          On entry, the M-by-N matrix C.
!>          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q.
!>

LDC

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

WORK

!>         (workspace) COMPLEX*16 array, dimension (MAX(1,LWORK))
!>
!>

LWORK

!>          LWORK is INTEGER
!>          The dimension of the array WORK.
!>
!>          If SIDE = 'L', LWORK >= max(1,N)*NB;
!>          if SIDE = 'R', LWORK >= max(1,MB)*NB.
!>          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.

Further Details:

!> Tall-Skinny QR (TSQR) performs QR by a sequence of unitary transformations,
!> representing Q as a product of other unitary matrices
!>   Q = Q(1) * Q(2) * . . . * Q(k)
!> where each Q(i) zeros out subdiagonal entries of a block of MB rows of A:
!>   Q(1) zeros out the subdiagonal entries of rows 1:MB of A
!>   Q(2) zeros out the bottom MB-N rows of rows [1:N,MB+1:2*MB-N] of A
!>   Q(3) zeros out the bottom MB-N rows of rows [1:N,2*MB-N+1:3*MB-2*N] of A
!>   . . .
!>
!> Q(1) is computed by GEQRT, which represents Q(1) by Householder vectors
!> stored under the diagonal of rows 1:MB of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,1:N).
!> For more information see Further Details in GEQRT.
!>
!> Q(i) for i>1 is computed by TPQRT, which represents Q(i) by Householder vectors
!> stored in rows [(i-1)*(MB-N)+N+1:i*(MB-N)+N] of A, and by upper triangular
!> block reflectors, stored in array T(1:LDT,(i-1)*N+1:i*N).
!> The last Q(k) may use fewer rows.
!> For more information see Further Details in TPQRT.
!>
!> For more details of the overall algorithm, see the description of
!> Sequential TSQR in Section 2.2 of [1].
!>
!> [1] “Communication-Optimal Parallel and Sequential QR and LU Factorizations,”
!>     J. Demmel, L. Grigori, M. Hoemmen, J. Langou,
!>     SIAM J. Sci. Comput, vol. 34, no. 1, 2012
!>

Definition at line 197 of file zlamtsqr.f.

Author¶

Generated automatically by Doxygen for LAPACK from the source code.

Version 3.12.0

LAPACK

Source file:	lamtsqr.3.en.gz (from lapack-man 3.12.0-160000.1.3)
Source last updated:	2024-11-04T16:48:43Z
Converted to HTML:	2025-03-25T08:55:52Z