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.
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 cl::sycl::vector_class<cl::sycl::event> &events = {})
}
ungqr
(USM version) supports the following precisions and
devices:
T |
Devices supported |
---|---|
|
Host, CPU, and GPU |
|
Host, CPU, and GPU |
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, ...)
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
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 |
Return Values
Output event to wait on to ensure computation is complete.