Developer Reference

Contents

geqrf_batch (Buffer Strided Version)

Computes the batch of QR factorizations of a general m-by-n matrices. This routine belongs to the
oneapi::mkl::lapack
namespace.

Description

The routine forms the
Q
i
R
i
factorizations of a general
m
-by-
n
matrices
A
i
. No pivoting is performed.
The routine does not form the matrix
Q
i
explicitly. Instead,
Q
i
is represented as a product of min(
m
,
n
) elementary reflectors. Routines are provided to work with
Q
i
in this representation.

API

Syntax
namespace oneapi::mkl::lapack { void geqrf_batch(cl::sycl::queue &queue, std::int64_t m, std::int64_t n, 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
float
Host, CPU, and GPU
double
Host, CPU, and GPU
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
).
a
Array holding input matrices
A
i
.
lda
The leading dimension of
A
i
.
stride_a
The stride between the beginnings of matrices
A
i
inside the batch array
a
.
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 geqrf_batch_scratchpad_size (Strided Version).
Output Parameters
a
Overwritten by the factorization data as follows:
The elements on and above the diagonal of the array contain the
min(m,n)
-by-
n
upper trapezoidal matrices
R
i
(
R
i
is upper triangular if
m≥n
); the elements below the diagonal, with the array tau
i
, present the orthogonal matrix
Q
i
as a product of
min(m,n)
elementary reflectors.
tau
Array to store batch of
tau
i
, each of size
min(m,n)
, containing scalars that define elementary reflectors for the matrices
Q
i
in its decomposition in a product of elementary reflectors.
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 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.