Developer Reference

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ungqr (USM Version)

Generates the complex unitary matrix Q of the QR factorization formed by the
geqrf
(USM Version) function. . This routine belongs to the
oneapi::mkl::lapack
namespace.

Description

The routine generates the whole or part of
m
-by-
m
unitary matrix
Q
of the
QR
factorization formed by the geqrf (USM Version) function.
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:
ungqr(queue, m, m, p, a, lda, tau, ...)
To compute the leading
p
columns of
Q
(which form an orthonormal basis in the space spanned by the columns of
A
):
ungqr(queue, m, p, p, a, lda, tau, ...)
To compute the matrix
Q
k
of the
QR
factorization of the leading
k
columns of the matrix
A
:
ungqr(queue, m, m, k, a, lda, tau, ...)
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
):
ungqr(queue, m, k, k, a, lda, tau, ...)

API

Syntax
namespace oneapi::mkl::lapack { cl::sycl::event ungqr(cl::sycl::queue &queue, std::int64_t m, std::int64_t n, std::int64_t k, T *a, std::int64_t lda, T *tau, T *scratchpad, std::int64_t scratchpad_size, const std::vector<cl::sycl::event> &events = {}) }
ungqr
(USM version) supports the following precisions and devices:
T
Devices supported
std::complex<float>
Host, CPU, and GPU
std::complex<double>
Host, CPU, and GPU
Input Parameters
queue
Device queue where calculations will be performed.
m
The number of rows in the matrix
A
(
0≤m
).
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
Pointer to the result of geqrf (USM Version).
lda
The leading dimension of a (
lda≤m
).
tau
Pointer to the result of geqrf (USM Version).
scratchpad
Pointer to scratchpad memory to be used by the 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 the ungqr_scratchpad_size function.
events
List of events to wait for before starting computation. Defaults to empty list.
Output Parameters
a
Overwritten by n leading columns of the m-by-m unitary matrix
Q
.
Exceptions
Exception
Description
mkl::lapack::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 = -i
, the
i
-th parameter had an illegal value.
If
info
is equal to the value passed as scratchpad size, and detail() returns non-zero, then the passed scratchpad has an insufficient size, and the required size should not be less than the value returned by the detail() method of the exception object.
Return Values
Output event to wait on to ensure computation is complete.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.