ungqr_batch (Buffer Strided Version)

Generates the complex unitary matrices Qi of the batch of QR factorizations formed by geqrf_batch function (Buffer stride version). This routine belongs to the oneapi::mkl::lapacknamespace.

Syntax

void ungqr_batch(cl::sycl::queue &queue, std::int64_t m, std::int64_t n, std::int64_t k, cl::sycl::buffer<T> &a, std::int64_t lda, std::int64_t stride_a, cl::sycl::buffer<T> &tau, std::int64_t stride_tau, std::int64_t batch_size, cl::sycl::buffer<T> &scratchpad, std::int64_t scratchpad_size)

Function supports the following precisions and devices.

T

Devices supported

std::complex<float>

Host, CPU, and GPU

std::complex<double>

Host, CPU, and GPU

Description

The routine generates the wholes or parts of m-by-m unitary matrix Qi of the QR factorization formed by the geqrf_batch (Buffer Strided Version) function.

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

ungqr_batch(queue, m, m, p, a, ...)

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

ungqr_batch(queue, m, p, p, a, ...)

To compute the matrix Qik of the QR factorization of the leading k columns of the matrices Ai:

ungqr_batch(queue, m, m, k, a, ...)

To compute the leading k columns of Qik (which form an orthonormal basis in the space spanned by the leading k columns of the matrices Ai):

ungqr_batch(queue, m, k, k, a, ...)

Input Parameters

queue

Device queue where calculations will be performed.

m

The number of rows in the matrices Ai (0 m).

n

The number of columns in the matrices Ai (0 n).

k

the number of elementary reflectors whose product defines the matrices Qi (0 ≤ kn) .

a

Array resulting after a call to geqrf_batch (Buffer Strided Version).

lda

The leading dimension of Ai (ldam).

stride_a

The stride between the beginnings of matrices Ai inside the batch array a.

tau

Array resulting after a call to geqrf_batch (Buffer Strided Version).

stride_tau

The stride between the beginnings of arrays taui inside the array tau.

batch_size

Specifies the number of problems in a batch.

scratchpad

Scratchpad memory to be used by routine for storing intermediate results.

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_batch_scratchpad_size (Strided Version).

Output Parameters

a

Array data is overwritten by a batch of n leading columns of the m-by-m unitary matrices Qi.

Exceptions

mkl::lapack::batch_exception

This exception is thrown when problems occur during calculations. You can obtain the info code of the problem using the info() method of the exception object: If info = -n, the n-th parameter had an illegal value. If info equals the value passed as scratchpad size, and detail() returns non-zero, then the passed scratchpad is of insufficient size, and the required size should be not less then value returned by the detail() method of the exception object.