Developer Reference

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gerqf

Computes the RQ factorization of a general m-by-n matrix. This routine belongs to the
oneapi::mkl::lapack
namespace.

Description

The routine forms the
RQ
factorization of a general
m
-by-
n
matrix
A
No pivoting is performed.
The routine does not form the matrix
Q
explicitly. Instead,
Q
is represented as a product of min(
m
,
n
) elementary reflectors. Routines are provided to work with
Q
in this representation.
This routine supports the Progress Routine feature.

API

Syntax
namespace oneapi::mkl::lapack { void gerqf(cl::sycl::queue &queue, std::int64_t m, std::int64_t n, cl::sycl::buffer<T> &a, std::int64_t lda, cl::sycl::buffer<T> &tau, cl::sycl::buffer<T> &scratchpad, std::int64_t scratchpad_size) }
gerqf
supports the following precisions and devices:
T
Devices supported
float
Host and CPU
double
Host and CPU
std::complex<float>
Host and CPU
std::complex<double>
Host and CPU
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
).
a
Buffer holding input matrix
A
. The second dimension of
a
must be at least
max(1, n)
.
lda
The leading dimension of
a
, at least
max(1, m)
.
scratchpad
Buffer holding 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 gerqf_scratchpad_size function.
Output Parameters
a
Overwritten by the factorization data as follows:
if
m ≤ n
, the upper triangle of the subarray
a(1:m, n-m+1:n )
contains the
m
-by-
m
upper triangular matrix
R
; if
m ≥ n
, the elements on and above the (
m
-
n
)-th subdiagonal contain the
m
-by-
n
upper trapezoidal matrix
R
In both cases, the remaining elements, with the array
tau
, represent the orthogonal/unitary matrix
Q
as a product of
min(m,n)
elementary reflectors.
tau
Array, size at least
min(m,n)
.
Contains scalars that define elementary reflectors for the matrix
Q
in its decomposition in a product of elementary reflectors.
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.

Product and Performance Information

1

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