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I know ?geqrf to calculate m-by-n A = QR and then ungqr to generate Q. but the Q is m-by-m square matrix, what i want is Q m-by-n.

I really don't know how to deal with this, I found p?geqrf and p?ungqr would generate Q with m-by-n, but I think it's a parallel ?geqrf, it might not help me. could anyone help me, please? thanks very much..

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Hello Leo,

The functions is supposed to be able to get m x n Q too . please see the doc:

?orgqr

Generates the real orthogonal matrix Q of the QR

factorization formed by ?geqrf.

The routine generates the whole or part of m-by-m orthogonal matrix Qof the QRfactorization formed by

the routines geqrf/geqrfor geqpf/geqpf. Use this routine after a call to sgeqrf/dgeqrfor sgeqpf/dgeqpf.

Usually Q is determined from the QR factorization of an **mby p matrix A with m ≥ p**. To compute the whole

matrix Q, use:

call ?orgqr(m, m, p, a, lda, tau, work, lwork, info)

**To compute the leading p columns of Q(which form an orthonormal basis in the space spanned by the
columns of A):
call ?orgqr(m, p, p, a, lda, tau, work, lwork, info)**

To compute the matrix Q k of the QRfactorization of leading k columns of the matrix A:

call ?orgqr(m, m, k, a, lda, tau, work, lwork, info)

To compute the leading k columns of Q k

(which form an orthonormal basis in the space spanned by leading k

columns of the matrix A):

call ?orgqr(m, k, k, a, lda, tau, work, lwork, info)

?ungqr

Generates the complex unitary matrix Q of the QR

factorization formed by ?geqrf

The routine generates the whole or part of m-by-munitary matrix Qof the QRfactorization formed by the

routines geqrf/geqrfor geqpf/geqpf. Use this routine after a call to cgeqrf/zgeqrfor cgeqpf/zgeqpf.

Usually Qis determined from the QRfactorization of an mby pmatrix Awith m ≥ p. To compute the whole

matrix Q, use:

call ?ungqr(m, m, p, a, lda, tau, work, lwork, info)

To compute the leading pcolumns of Q(which form an orthonormal basis in the space spanned by the

columns of A):

call ?ungqr(m, p, p, a, lda, tau, work, lwork, info)

To compute the matrix Q

k

of the QRfactorization of the leading kcolumns of the matrix A:

call ?ungqr(m, m, k, a, lda, tau, work, lwork, info)

To compute the leading kcolumns of Q

k

(which form an orthonormal basis in the space spanned by the

leading kcolumns of the matrix A):

call ?ungqr(m, k, k, a, lda, tau, work, lwork, info)

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Hello Leo,

The functions is supposed to be able to get m x n Q too . please see the doc:

?orgqr

Generates the real orthogonal matrix Q of the QR

factorization formed by ?geqrf.

The routine generates the whole or part of m-by-m orthogonal matrix Qof the QRfactorization formed by

the routines geqrf/geqrfor geqpf/geqpf. Use this routine after a call to sgeqrf/dgeqrfor sgeqpf/dgeqpf.

Usually Q is determined from the QR factorization of an **mby p matrix A with m ≥ p**. To compute the whole

matrix Q, use:

call ?orgqr(m, m, p, a, lda, tau, work, lwork, info)

**To compute the leading p columns of Q(which form an orthonormal basis in the space spanned by the
columns of A):
call ?orgqr(m, p, p, a, lda, tau, work, lwork, info)**

To compute the matrix Q k of the QRfactorization of leading k columns of the matrix A:

call ?orgqr(m, m, k, a, lda, tau, work, lwork, info)

To compute the leading k columns of Q k

(which form an orthonormal basis in the space spanned by leading k

columns of the matrix A):

call ?orgqr(m, k, k, a, lda, tau, work, lwork, info)

?ungqr

Generates the complex unitary matrix Q of the QR

factorization formed by ?geqrf

The routine generates the whole or part of m-by-munitary matrix Qof the QRfactorization formed by the

routines geqrf/geqrfor geqpf/geqpf. Use this routine after a call to cgeqrf/zgeqrfor cgeqpf/zgeqpf.

Usually Qis determined from the QRfactorization of an mby pmatrix Awith m ≥ p. To compute the whole

matrix Q, use:

call ?ungqr(m, m, p, a, lda, tau, work, lwork, info)

To compute the leading pcolumns of Q(which form an orthonormal basis in the space spanned by the

columns of A):

call ?ungqr(m, p, p, a, lda, tau, work, lwork, info)

To compute the matrix Q

k

of the QRfactorization of the leading kcolumns of the matrix A:

call ?ungqr(m, m, k, a, lda, tau, work, lwork, info)

To compute the leading kcolumns of Q

k

(which form an orthonormal basis in the space spanned by the

leading kcolumns of the matrix A):

call ?ungqr(m, k, k, a, lda, tau, work, lwork, info)

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