Intel® oneAPI Math Kernel Library (oneMKL) - Data Parallel C++ Developer Reference

Developer Reference

Contents

gerqf (USM Version)

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.

API

Syntax
namespace oneapi::mkl::lapack {
  cl::sycl::event gerqf(cl::sycl::queue &queue,
  std::int64_t m,
  std::int64_t n,
  T *a,
  std::int64_t lda,
  T *tau,
  T *scratchpad,
  std::int64_t scratchpad_size,
  const std::vector<cl::sycl::event> &events = {})
}
gerqf
 (USM version) 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
Pointer to the memory 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
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 gerqf_scratchpad_size function.
events
List of events to wait for before starting computation. Defaults to empty list.
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 get_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 get_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 get_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.