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

Developer Reference

Contents

ungqr_batch (Buffer Strided Version)

Generates the complex unitary matrices Q
i
 of the batch of QR factorizations formed by
geqrf_batch
 function (Buffer stride version). This routine belongs to the
oneapi::mkl::lapack
 namespace.

Description

The routine generates the wholes or parts of
m
-by-
m
 unitary matrix
Q
i
 of the
QR
 factorization formed by the geqrf_batch (Buffer Strided Version) function.
Usually
Q
i
 is determined from the
QR
 factorization of an
m
 by
p
 matrix
A
i
 with
m≥p
. To compute the whole matrices
Q
i
, use:
ungqr_batch(queue, m, m, p, a, ...)
To compute the leading
p
 columns of
Q
i
 (which form an orthonormal basis in the space spanned by the columns of
A
i
):
ungqr_batch(queue, m, p, p, a, ...)
To compute the matrix
Q
i
k
 of the
QR
 factorization of the leading
k
 columns of the matrices
A
i
:
ungqr_batch(queue, m, m, k, a, ...)
To compute the leading
k
 columns of
Q
i
k
 (which form an orthonormal basis in the space spanned by the leading
k
 columns of the matrices
A
i
):
ungqr_batch(queue, m, k, k, a, ...)

API

Syntax
namespace oneapi::mkl::lapack {
  void ungqr_batch(cl::sycl::queue &queue,
  std::int64_t m,
  std::int64_t n,
  std::int64_t k,
  cl::sycl::buffer<T> &a,
  std::int64_t lda,
  std::int64_t stride_a,
  cl::sycl::buffer<T> &tau,
  std::int64_t stride_tau,
  std::int64_t batch_size,
  cl::sycl::buffer<T> &scratchpad,
  std::int64_t scratchpad_size)
}
Function 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 matrices
A
i
 (
0 ≤ m
).
n
The number of columns in the matrices
A
i
 (
0 ≤ n
).
k
the number of elementary reflectors whose product defines the matrices
Q
i
 (0 ≤
k
 ≤
n
) .
a
Array resulting after a call to geqrf_batch (Buffer Strided Version).
lda
The leading dimension of
A
i
 (
lda
 ≤
m
).
stride_a
The stride between the beginnings of matrices
A
i
 inside the batch array
a
.
tau
Array resulting after a call to geqrf_batch (Buffer Strided Version).
stride_tau
The stride between the beginnings of arrays
tau
i
 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 ungqr_batch_scratchpad_size (Strided Version).
Output Parameters
a
Array data is overwritten by a batch of
n
 leading columns of the
m
-by-
m
 unitary matrices
Q
i
.
Exceptions
Exception
Description
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.

Product and Performance Information

1

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