geqrf_batch (USM Strided Version)

Computes the batch of QR factorizations of a general m-by-n matrices. This routine belongs to the oneapi::mkl::lapacknamespace.

Syntax

cl::sycl::event geqrf_batch(cl::sycl::queue &queue, std::int64_t m, std::int64_t n, T *a, std::int64_t lda, std::int64_t stride_a, T *tau, std::int64_t stride_tau, std::int64_t batch_size, T *scratchpad, std::int64_t scratchpad_size, const cl::sycl::vector_class<cl::sycl::event> &events = {})

Function supports the following precisions and devices.

T

Devices supported

float

Host, CPU, and GPU

double

Host, CPU, and GPU

std::complex<float>

Host, CPU, and GPU

std::complex<double>

Host, CPU, and GPU

Description

The routine forms the QiRi factorizations of a general m-by-n matrix Ai. No pivoting is performed.

The routine does not form the matrix Qi explicitly. Instead, Qi is represented as a product of min(m, n) elementary reflectors. Routines are provided to work with Qi in this representation.

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).

a

Array holding input matrices Ai.

lda

The leading dimension of Ai .

stride_a

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

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 geqrf_batch_scratchpad_size (Strided Version).

events

List of events to wait for before starting computation. Defaults to empty list.

Output Parameters

a

Overwritten by the factorization data as follows:

The elements on and above the diagonal of the array contain the min(m,n)-by-n upper trapezoidal matrices Ri (Ri is upper triangular if m≥n); the elements below the diagonal, with the array taui, present the orthogonal matrix Qi as a product of min(m,n) elementary reflectors.

tau

Array to store batch of taui, each of size min(m,n), containing scalars that define elementary reflectors for the matrices Qi in its decomposition in a product of elementary reflectors.

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.

Return Values

Output event to wait on to ensure computation is complete.