Man page - lamtsqr(3)

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Manual

lamtsqr

NAME
SYNOPSIS
Functions
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)
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)
subroutine slamtsqr (character side, character trans, integer m, integer n,integer k, integer mb, integer nb, real, dimension( lda, * ) a, integerlda, real, dimension( ldt, * ) t, integer ldt, real, dimension( ldc, *) c, integer ldc, real, dimension( * ) work, integer lwork, integerinfo)
subroutine zlamtsqr (character side, character trans, integer m, integer n,integer k, integer mb, integer nb, complex*16, dimension( lda, * ) a,integer lda, complex*16, dimension( ldt, * ) t, integer ldt,complex*16, dimension( ldc, * ) c, integer ldc, complex*16, dimension(* ) work, integer lwork, integer info)
Author

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

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

N

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

K

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

MB

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

NB

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

A

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

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

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))
On exit, if INFO = 0, WORK(1) returns the minimal LWORK.

LWORK

LWORK is INTEGER
The dimension of the array WORK.
If MIN(M,N,K) = 0, LWORK >= 1.
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 minimal 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

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

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

N

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

K

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

MB

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

NB

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

A

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

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

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))
On exit, if INFO = 0, WORK(1) returns the minimal LWORK.

LWORK

LWORK is INTEGER
The dimension of the array WORK.
If MIN(M,N,K) = 0, LWORK >= 1.
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 minimal 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

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

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

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

N

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

K

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

MB

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

NB

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

A

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

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

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))
On exit, if INFO = 0, WORK(1) returns the minimal LWORK.

LWORK

LWORK is INTEGER
The dimension of the array WORK.
If MIN(M,N,K) = 0, LWORK >= 1.
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 minimal 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

subroutine zlamtsqr (character side, character trans, integer m, integer n,integer k, integer mb, integer nb, complex*16, dimension( lda, * ) a,integer lda, complex*16, dimension( ldt, * ) t, integer ldt,complex*16, dimension( ldc, * ) c, integer ldc, complex*16, 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

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

N

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

K

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

MB

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

NB

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

A

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

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

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))
On exit, if INFO = 0, WORK(1) returns the minimal LWORK.

LWORK

LWORK is INTEGER
The dimension of the array WORK.
If MIN(M,N,K) = 0, LWORK >= 1.
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 minimal 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

Author

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