ungqr¶

Generates the complex unitary matrix Q of the QR factorization formed by geqrf.

ungqr supports the following precisions.

T

std::complex<float>

std::complex<double>

Description

The routine generates the whole or part of m-by-m unitary matrix Q of the QR factorization formed by the routines geqrf.

Usually Q is determined from the QR factorization of an m by p matrix A with m≥p. To compute the whole matrix Q, use:

onemkl::ungqr(queue, m, m, p, a, lda, tau, scratchpad, scratchpad_size)

To compute the leading p columns of Q (which form an orthonormal basis in the space spanned by the columns of A):

onemkl::ungqr(queue, m, p, p, a, lda, tau, scratchpad, scratchpad_size)

To compute the matrix Q^k of the QR factorization of the leading k columns of the matrix A:

onemkl::ungqr(queue, m, m, k, a, lda, tau, scratchpad, scratchpad_size)

To compute the leading k columns of Q^k (which form an orthonormal basis in the space spanned by the leading k columns of the matrix A):

onemkl::ungqr(queue, m, k, k, a, lda, tau, scratchpad, scratchpad_size)

ungqr (BUFFER Version)¶

Syntax

void onemkl::lapack::ungqr(cl::sycl::queue &queue, std::int64_t m, std::int64_t n, std::int64_t k, cl::sycl::buffer<T, 1> &a, std::int64_t lda, cl::sycl::buffer<T, 1> &tau, cl::sycl::buffer<T, 1> &scratchpad, std::int64_t scratchpad_size)¶

Input Parameters

queue: The queue where the routine should be executed.
m: The number of rows in the matrix A (m ≤0).
n: The number of columns in the matrix A (0≤n).
k: The number of elementary reflectors whose product defines the matrix Q (0≤k≤n).
a: The buffer a as returned by geqrf.
lda: The leading dimension of a (lda ≤m).
tau: The buffer tau as returned by geqrf.
scratchpad_size: Size of scratchpad memory as a number of floating point elements of type T. Size should not be less than the value returned by ungqr_scratchpad_size function.

Output Parameters

a: Overwritten by n leading columns of the m-by-m orthogonal matrix Q.
scratchpad: Buffer holding scratchpad memory to be used by routine for storing intermediate results.

Throws

onemkl::lapack::exception

Exception is thrown in case of problems happened during calculations. The info code of the problem can be obtained by get_info() method of exception object:

If info=-i, the i-th parameter had an illegal value.

If info equals to value passed as scratchpad size, and get_detail() returns non zero, then passed scratchpad is of insufficient size, and required size should not be less than value return by get_detail() method of exception object.

ungqr (USM Version)¶